Module 2 The Endocrine System

Module 2 -The Endocrine System

In This Module

This module addresses how the endocrine system contributes to homeostasis by studying the following lessons.

Lesson 1—Structure and Organization of the Endocrine System

In the big picture you were introduced to Emily and her struggle with FMEN1 disorder. You yourself may experience stress when you are cramming for exams, or are worried about a friend in crisis. When the exam or the crisis has passed, you calm down and your endocrine system returns to normal. In Emily’s case, her body experiences constant stress with no relief in sight. You both have the same endocrine glands, but what causes the difference in communication?

In order to explore these concepts, you will investigate the following focusing question:

• How is the endocrine system organized, and how do its parts communicate with each other and with other various parts of the body?

Lesson 2—Who is in Charge?

Much as the brain is the boss of the nervous system, the endocrine system needs a master or a boss in order to ensure homeostasis. The kingpin of the operation is the hypothalamus/pituitary gland complex. If the pituitary/hypothalamus complex was not doing its job, your life would quickly unravel. You would not be able to develop or function normally. Your growth might be stunted, and your voice would never change if you were a boy.

In this lesson you will explore the following question:

• Who is the boss of the endocrine system, and how is control of the endocrine system managed?

Lesson 3—The Adrenal Gland

When you studied the sympathetic nervous system in Module 1, you learned about the “flight or fight” reaction: the tendency in stressful situations to either run away or stay and work through the stressful situation. Imagine watching a horror movie and anticipating the feeling of being scared out of your skin. If your life were a horror movie, you would constantly be on edge—anxious and just waiting to be scared. It would be like going through life with a constant adrenaline rush. How long do you think that you could last through that?

In this lesson you will focus on the following question:

• How does the adrenal gland and its secretions affect the body?

Lesson 4—The Thyroid and Parathyroid Glands

Chilly? Hot? Overweight? Lethargic? Hyperactive? These are different symptoms of two opposite types of thyroid disorders: Hyperthyroidism [hyper means over activity] and Hypothyroidism. [hypo means under activity] If you have hyperthyroidism you may always feel too hot, you may experience weight loss, you may find it difficult to concentrate, and you may be jittery and hyperactive. If you have hypothyroidism you might always be cold, you may be overweight, you likely have a tendancy to feel tired and lethargic, and you may have trouble staying awake.

To understand the role of the thyroid gland in the functioning of the endocrine system we will explore the following focusing question:

• How do the thyroid and parathyroid glands contribute to homeostasis?

Lesson 5—The Pancreas

It is just before lunch, you are feeling hungry, tired, light-headed, and you are worried about a big exam in the afternoon. This is stress! What do you grab to eat? Are you the quick candy bar type or the protein-based tuna sandwich type?  Which one do you think would get rid of those symptoms you are experiencing, and get you through the exam without a complete collapse or meltdown? This situation deals specifically with the pancreas and how it manages blood sugar levels. For a diabetic this is a daily balancing act, and one that can have very serious consequences if it is not regulated.

To understand the role of the pancreas in the endocrine system, you will investigate the following focusing question:

• How does the pancreas contribute to homeostasis?

Lesson 6—Bringing it all Together

The endocrine system responds to stimuli by using chemical messengers in the blood to control metabolic processes in the body. Your body is kept in balance because your nervous system responds to immediate stimuli or crises while your hormonal system maintains long term stability.

This lesson will explore how the nervous and endocrine systems complement one another and communicate with each other to maintain homeostasis and ensure your well being by investigating the following focusing question:

• How are the nervous and endocrine systems interdependent, and how are they different?

Big Picture

Big Picture

Stressed! Stressed out! and ready to explode—we deal with stress everyday. You might deal with it by eating a bag of cookies, or you might find that your body just needs sleep to recover. Your body needs to adjust to external and internal stresses or changes so that they do not become a detriment to your health. Staying healthy means appropriate choices in how you identify and cope with stress.

Consider the case study of Emily, a thirty year old woman who today lives with the constant stress of an endocrine disorder. Her career goals and life plans are continually interrupted by her health issues.

When she was in Grade 12, Emily developed extreme fatigue and complained that her whole body ached. Even her bones hurt! She felt weak and began finding it very difficult to keep up with the readings and the homework that her teachers assigned. She also noted that she couldn’t focus the microscope in the lab, and that at times, her vision was blurred. It was at this point that her parents took her to see a series of physicians and medical specialists. After extensive tests and consultations, Emily’s doctors confirmed that she had a rare inherited endocrine disorder called familial multiple endocrine neoplasia type 1 (FMEN1). In Unit C, you will learn how Emily inherited this disorder, and you will come to understand how this disorder has impacted Emily’s daily life as well as her longevity.

In FMEN1 specific endocrine glands, such as the parathyroid glands, pituitary gland, pancreas, adrenal glands, or a combination of them become overactive due to the growth of mostly benign, or non-cancerous, tumors called neoplasms. These tumors disrupt normal function by crowding nearby structures and cells. For example, a tumor in the pituitary gland can press against surrounding pituitary tissue, thereby damaging the normal part of the tiny pituitary gland, or the nerves that carry visual information from the eyes. In the picture, notice the very close alignment of the pituitary gland and the optic nerve. This is one reason why Emily’s vision was blurred.

In this module you will explore the big question of how the body uses chemical messengers to respond to stimuli, including stress, to establish homeostasis.

Throughout the module you will explore the following focusing questions:

• How is the endocrine system organized, and how do its parts communicate with each other and other parts of the body?

• Who is the “boss” of the endocrine system, and how is control of the endocrine system managed?

• How do the major endocrine glands, including the anterior and posterior pituitary gland, the thyroid gland, the parathyroid glands, the pancreas, and the adrenal glands contribute to homeostasis?

• What are the metabolic roles fulfilled by hormones in the maintenance of homeostasis, and,what are the physiological consequences of hormonal imbalances?

• How do the nervous and the endocrine systems interact to maintain overall homeostasis?

Lesson 1.2.1

Lesson 1—Structure and Organization of the Endocrine System

Get Focused

In the big picture, you were introduced to Emily and her struggle with familial multiple endocrine neoplasia type 1 (FMEN1) disorder. You might think that you experience stress when you are cramming for exams or worried about a friend. You may get a headache, your heart may race or you may have a sleepless night. Your endocrine system reacts to the stress by secreting many hormones that help you cope with the stress. When the exam or the crisis has passed, you seem to calm down because your endocrine system has returned the level of “stress” hormones to normal. In Emily’s case, her body experiences constant stress with no chance of relief. How might Emily’s endocrine system be different from yours? You both have the same organs, but it is obvious something is not working or communicating properly in Emily’s case.

In order to explore these concepts, you will investigate the following focusing question:

• How is the endocrine system organized, and how its parts communicate with each other and with various parts of the body?

Module 2: Lesson 1 Assignment

While you are completing this lesson, there will be many opportunities for you to acquire, understand and practice the concepts that are presented to you. After completing these assignments as well as your summary notes, file everything in your course folder to reference when you are preparing for exams.

Remember you also have the option of trying additional questions from the textbook for further practice. Consult with your instructor for the answers to these questions. “The Key” will also provide you with many diploma style multiple choice, numerical response, and written response questions that will be an excellent review of the module, and good preparation for the Diploma exam.

The other questions in this lesson are not marked by the teacher; however you should still answer these questions. The Self-Check and Try This questions are placed in this lesson to help you review important information and build key concepts that may be applied in future lessons.

After a discussion with your teacher, you must decide what to do with the questions that are not part of your assignment. For example, you may decide to submit to your teacher the responses to Try This questions that are not marked. You should record the answers to all of the questions in this lesson and place those answers in your course folder.

Complete the  Bio 30 1.2.1 Online Assignment when you have completed all of the learning activities for this lesson.

You should also watch the tutorial video for the lesson and submit a tutorial summary.  Bio30 tut# 1.2.1 Hormone Regulation

1.2.1 page 2

Explore

Crash Course - The Endocrine System

Introduction

Consider how you feel when you worry about exams, deadlines, sick friends, or a relationship with a girlfriend/boyfriend. Your body responds with a racing heart beat, sweaty hands, fast breathing, and maybe sleeplessness.

In this activity, you will measure one or, if possible, both of the following physiological changes: pulse, which is an indirect measure of heart rate (as you learned in Biology 20) and blood pressure. Measuring blood pressure will be dependant on availability of a blood pressure monitor. When you have completed the lab you will submit the data table, four analysis questions and the conclusion for assessment.

Problem (Purpose) (Optional)

How does a stressful situation affect pulse (and blood pressure)?

Materials

• test questions that you can get from your instructor

• clock/watch with a second hand

• blood pressure monitor (If you do not have a blood pressure monitor at home, you can contact your instructor for options. Many drug stores and pharmacies have blood pressure facilities or equipment available. As well, your local health unit may allow you to use a blood pressure monitor.)

Procedure

1. Work with a partner or a small group. You will be the experimenter and the other members will be the subjects.
2. Using a watch with a second hand, the experimenter will time the subject as he/she sits in a comfortable chair with eyes closed and taking deep, relaxing breaths for 2 minutes.
   
   At the end of the relaxation period, the experimenter will take and record the subject’s pulse, and if possible his/her blood pressure. To review how to take a pulse, you can go to any of your favourite “how to” sites. If you are measuring the pulse manually, you can count the number of pulses in 15 seconds and then multiply by 4 to get the heart rate per minute. In the picture, notice where you place the fingers in order to feel the strongest pulse.
   
   If you are using a digital blood pressure monitor, the instructions are usually included with the machine. Blood pressure monitors are often equipped to measure your pulse as well as your blood pressure. If you are using a blood pressure monitor, you can leave the cuff on the subject for the next step. These values will provide baseline data of your subject in a relaxed state.

3. The experimenter will note the time and administer the test to the subject. The subject will have 2 minutes to complete the test. The experimenter should harass the subject by telling him/her to “hurry” and/or telling him/her that they only have so many seconds left to complete the test.
4. At the end of the 2 minutes, shout “Time is up!” and immediately take and record the subject’s pulse and, if possible, blood pressure, and then again after 2 minutes, and once again two minutes after that. You should have a total of four readings.

Data
Complete the data table

Analysis

Complete the questions in the online assignment

Conclusion

In this lab, both the nervous and endocrine systems brought about the physiological changes that you measured. What conclusion can you make from this lab as to how a stressful situation affects pulse and blood pressure? Which parts of the nervous and endocrine systems were involved? What can you conclude about the body’s ability to recover from stressful situations? How were the nervous and endocrine systems involved in this recovery? Write a response to these questions in the Assignment document.

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Negative Feedback Loops

In the Student Stress! lab you learned that a stressful situation such as taking a test in a very short time and being harassed by the experimenter changes physiological processes such as blood pressure and heart rate. After the stressful situation passes, heart rate and blood pressure return to normal or at-rest values.

Every moment of your life your body regulates levels of carbon dioxide and oxygen, maintains water and salt balance, controls blood glucose levels, regulates temperature, maintains a regular heart beat, and sustains a normal blood pressure. An organism is said to be in homeostasis when the internal environment is maintained at the balanced or best condition for each of these factors, called the set point. Homeostasis provides cells within the body with a relatively constant environment and this helps them to work efficiently, no matter what is going on outside the body. Processes which aim to keep a potentially fluctuating feature within narrow limits use negative feedback mechanisms. Negative feedback means that when something changes, the opposite effect is instigated. In a negative feedback system there needs to be a sensor/receptor which measures the value of the feature to be controlled—for example chemoreceptors monitor the glucose concentration in the blood. If the sensor finds that the value is higher than it should be, it sends the information to an effector, which does something to lower the value back towards the correct level. It keeps on doing this until the sensor, which is still measuring the value, finds that the value is too low, and sends information to the effector to stop doing whatever it is doing and start doing something to raise the value once more.  Information is therefore “fed back” to the sensor from the effector. The feedback is called “negative” because it stops the effector from doing one thing and stimulates it to do the opposite. Notice how this is shown in the diagram below.

In the case of blood glucose regulation, an increase in the concentration of glucose sets into motion the processes which decrease it. Conversely a decrease in glucose concentration sets into motion the processes which increase it. The result is that, whatever the direction of the change (i.e. the error) the concentration of blood glucose automatically returns to its set value. This is shown in the diagram below.

Further discussion of homeostasis and feedback loops is found on page 203 of your textbook.

OR

Watch and Listen

Negative Feedback System?

Drawing a Feedback Loop

An increase in blood glucose can be represented by a feedback loop where the following conventions and symbols are used:

• a ascending arrow ↑ means an increase in the parameter
• a descending arrow ↓ means a decrease in the parameter
• a horizontal arrow → means “leads to”
• a dashed horizontal arrow → with either the words “negative feedback” and/or the negative symbol, sometimes in a circle, which means that the opposite effect has been performed.

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Try This

TR 1.

Now it is your turn to try your hand at drawing a feedback loop using all of the conventions and symbols described above. Given the following information on the hormone ADH (antidiuretic hormone) and its regulation of water volume in the body, summarize by drawing a negative feedback loop. After checking it your diagram, file it in your course folder for future reference when studying.

• a person is losing water by sweating profusely while playing 3-on-3 basketball on a sunny hot summer day

• this basketball player forgot to bring a water bottle and has no water to drink

• this situation results in a decrease in the plasma (watery part) of the blood so that the solute (dissolved substances) concentration of the blood increases. As a result, both the blood volume and the blood pressure decrease

• sensors (or receptors) in the hypothalamus called osmoreceptors sense the increased solute concentration, decreased blood volume, and decreased blood pressure

• the hypothalamus sends messages to the posterior pituitary gland to increase the release of the hormone ADH

• an increased level of ADH causes the kidneys (kidney tubules) to retain (reabsorb) more water and release less in the urine

• reabsorbed water in the blood increases blood volume, increases blood pressure, and decreases solute concentration

• information on the above three factors is fed back to the sensors in the hypothalamus

Positive Feedback:

Sometimes the deviation from the set point or normal value is not corrected. Instead it leads to a further deviation. The result is a “runaway” situation in which a change triggers more change in the same direction. This is called positive feedback. At first sight, positive feedback would appear to be damaging and even destructive. It may cause illness or the onset of a disorder. Returning to the glucose example, if the pancreas were not able to decrease blood glucose after a meal because it could not produce insulin, the glucose level would remain high. You would feel hungry and perhaps eat a candy bar. As the glucose was absorbed from the stomach and intestines, even higher blood glucose levels would result. You might know this as the disorder diabetes (mellitus). Emily has this disorder and you will study it in considerable detail in Lesson 5 of this module. Using all of the conventions and symbols that you learned for drawing negative feedback loops, a positive feedback loop for glucose regulation might look like the following:

However in some cases positive feedback is a good thing. In Unit B you will study the process of natural childbirth which is dependent on positive feedback involving the hormone oxytocin.

Try This

TR 2.

Using the information below, practice drawing a positive feedback loop to show how water regulation functions when the hormone ADH cannot be secreted. Use the symbols and conventions that you learned when drawing a negative feedback loop. After comparing your work with the key, file your work in your course folder.

• a person is losing water by sweating profusely while playing 3-on-3 basketball on a sunny hot summer day

• this basketball player forgot to bring a water bottle and has no water to drink

• this situation results in a decrease in the plasma (watery part) of the blood so that the solute (dissolved substances) concentration of the blood increases and both the blood volume and the blood pressure decrease

• sensors (or receptors) in the hypothalamus called osmoreceptors sense the increased solute concentration, decreased blood volume, and decreased blood pressure

• the hypothalamus sends messages to the posterior pituitary gland to increase the release of the hormone ADH

• a tiny tumor in the posterior pituitary prevents the release of ADH

• the kidney cannot reabsorb more water so it is released as an increased volume of urine

• this information is fed back to the sensors in the hypothalamus

1.2.1 page 5

Fluctuation Around the Set Point

Do you recall playing on the seesaw on your school playground? Remember how hard it was for you and your friend to balance the seesaw evenly? Usually it was a case of you being up and your friend being down around that balance point, or vice versa. Like the seesaw, negative feedback loops in living organisms do not usually succeed in keeping a particular feature constant. There is usually some fluctuation about the set point. This happens because it takes time for information to be passed from the sensor to the effector, and for the actions of the effector to have their effect. The longer this time delay, the greater the fluctuation will be.  Fluctuation around the set point is shown in the illustration to the right.

In humans the sensors/receptors are specialized cells. Some of these cells are in the brain, but cells in other organs, such as the pancreas, also act as detectors for particular substances. Many different organs act as effectors. For example, the skin is an effector in temperature regulation, while the kidneys are effectors in the regulation of water content. Information passes from sensors to effectors either along nerves, as in the fight or flight regulation of epinephrine from the adrenal medulla, or via hormones in the blood, as in regulation of water content for example. The overall response is coordinated by some kind of control centre or boss. In the endocrine system the control centre is the hypothalamus/pituitary complex.

Try This

TR 3.

To ensure that you understand how negative feedback loops contribute to homeostasis and how positive feedback affects this balance, answer the following questions. Where appropriate, remember to phrase your answers in complete sentences. Check and then file your work in your course folder.

1. Define homeostasis and explain how the endocrine system helps to maintain homeostasis in the body.

© Lori Sparkia/shutterstock

Use the following information describing how the temperature in your house is maintained to answer the next question.

• the thermostat is set at 20°C

• room temperature cools below the set value of 20°C

• the thermostat detects the lowered temperature

• an electronic signal is sent to the furnace

• the furnace is turned on and the temperature in the room increases

2. Draw and describe a negative feedback mechanism for a thermostat connected to the furnace in your house. How is this feedback mechanism similar to how some hormones are regulated in the body?

Use the following information to answer the next question.

• set point for human body temperature is 37°C
• thermoreceptors in skin sense temperature
• brain receives information
• effectors for regulating body temperature include:
  • sweat glands which when activated produce sweat for cooling the body
  • skin blood vessels which constrict to direct blood away from the skin, thus warming the body or they dilate to direct blood to the skin, thus cooling the body
  • shivering—a rapid contraction of muscles—warming the body,
  • behaviour such as putting on a hoodie to warm the body or putting on tank tops and shorts to cool the body

3. Draw a positive feedback loop that results in a fever.

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Endocrine Glands

In the previous module you learned about the basic unit of the nervous system—the neuron and how communication occurs through neural pathways. Now, you will learn about the major glands of the endocrine system and how communication through the use of special chemical messengers called hormones occurs.

 Endocrine glands are ductless glands; they do not release their secretions into a duct as exocrine glands do. Instead, endocrine glands secrete their hormones directly into the blood which acts as their transport medium. As the hormones pass cells, only those cells with special receptors will react to their presence. These cells are called target cells. Lipid-soluble hormones and water-soluble hormones activate their target cells very differently. Hormones interact together and in many instances, one hormone counteracts the action of a second hormone. Hormones such as these are called antagonistic hormones. This type of action is illustrated in the figure on the left.

Some hormones, called tropic hormones, influence other endocrine glands. These hormones are very important in the control and regulation of the endocrine system. They are secreted by the hypothalamus/pituitary complex. You can view the regulatory pathway of tropic hormones in Figure 13.10 on page 441 of your textbook. You may want to copy this pathway and store it in your course folder for later reference.

Read

To help you identify the main endocrine glands read pp. 436 – 441 in your textbook. Summarize your readings about the endocrine glands in a chart with the following headings: “endocrine gland”, “hormone produced by gland” and “primary effect of the hormone”. Place this chart in your course folder for future reference.

Watch and Listen

To further explore and review these concepts visually, watch the following video

Hormones

Try This

Instructions

TR 4

Practice labeling the endocrine glands, identifying the hormones they produce and describing the main functions of the hormones in the exercise that follows. After you have completed the exercise and have auto-checked it, file it in your course folder for access when you are studying.

Download the diagram of the endocrine system.

1. Label the major endocrine glands numbered 1 - 5 on the diagram.
2. List the hormones (the number of hormones to be identified is indicated in brackets) that each gland produces. The ovary and testis will be studied in Unit B. Although the thymus and pineal gland are part of the endocrine system, you are not responsible for studying them for this course.
3. Construct and complete a table with the following headings:
   
   

   Endocrine Gland

   Hormone

   Target Cells

   Primary Function

   
   

Self-Check Answers

TR 4b.

Labeling of the glands on the diagram and the hormones that the glands produce is as follows:

Structure #1: hypothalamus; secretes releasing and inhibiting factors/hormones

Structure #2a: anterior pituitary gland; secretes human growth hormone, thyroid stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), and follicle stimulating hormone (FSH), luteinizing hormone (LH), and prolactin, the last three hormones to be studied in detail in Unit B.

Structure #2b: posterior pituitary: releases oxytocin (to be studied in detail in Unit B) and antidiuretic hormone (ADH);

Structure #3: Parathyroid glands; secrete parathormone (PTH)

Structure #4: Thyroid gland; secretes thyroxine and calcitonin

Structure #6: Adrenal glands; adrenal cortex secretes cortisol, aldosterone, and gonadotropins (which are studied in Unit B); adrenal medulla secretes epinephrine and norepinephrine

Structure #7: Islet cells of pancreas; insulin and glucagon

Structure #8: Ovary secretes estrogen and progesterone; to be studied in Unit B

Structure #9: Testis secretes testosterone and inhibin; to be studied in Unit B

The completed table should incorporate the following:

Endocrine Glands, Their Hormones, Target Cells and Main Functions

1.2.1 page 7

Self-Check

To refresh your memory on the structure and organization of the endocrine system and the hormones that the endocrine glands produce, complete the following questions. Check them before going on to the assessment in Reflect and Connect.

1. Maintaining stable conditions in the internal environment of a cell is called
   
   
   1. positive feedback
   2. homeostasis
   3. reflex loops
   4. tropic control
2. Your body temperature is controlled by
   
   
   1. negative feedback
   2. positive feedback
   3. tropic hormones
   4. antagonistic hormones
3. The three components of a homeostatic mechanism in the body are
   
   
   1. a stimulus, a sensor, and a response
   2. a receptor, a neural pathway, and a control centre
   3. a sensor, a set point, and a response
   4. a sensor, an effector, and a control centre
4. Skeletal growth is promoted by a hormone secreted by the
   
   
   1. adrenal cortex
   2. adrenal medulla
   3. anterior pituitary
   4. posterior pituitary
5. A hormone that regulates glucose levels in the blood and a hormone that regulates sodium ions in the blood, and indirectly regulates water reabsorption by the kidneys are respectively,
   
   
   1. aldosterone and insulin
   2. glucagon and aldosterone
   3. insulin and antidiuretic hormone
   4. epinephrine and antidiuretic hormone
6. During an emergency situation, the adrenal gland is stimulated to release a hormone that directly causes an increase in
   
   
   1. conversion of glucose to glycogen
   2. insulin levels
   3. thyroxine levels
   4. blood glucose levels

Use the following information to answer the next question.

A tumor of the adrenal medulla is called phenochromocytoma. This tumor causes hypersecretion of epinephrine and norepinephrine, and a number of other symptoms.

7.  Possible symptoms of phenochromocytoma include
   
   
   1. increased heart rate, increased blood glucose, increased metabolic rate
   2. decreased heart rate, increased blood glucose, increased metabolic rate
   3. increased heart rate, decreased blood glucose, decreased metabolic rate
   4. decreased heart rate, decreased blood glucose, decreased metabolic rate
8. The release of milk from the breast after the birth of a baby is related to increased levels of
   
   
   1. estrogen
   2. progesterone
   3. oxytocin
   4. FSH and LH

True/False Questions

Identify each of the statements below as being true or false. If you think that the statement is false, change the statement to make it true.

1. The main purpose of the endocrine system is for the protection of the body.
2. Hormones are released into the blood stream.
3. Adrenocorticotropic hormone is released by the adrenal glands to control the pituitary gland.
4. Positive feedback leads to instability of the internal environment.
5. The anterior pituitary releases tropic hormones that were produced by the hypothalamus and stored.

1.2.1 page 8

  Reflect on the Big Picture

At the beginning of this module, you were introduced to Emily. She has all of the same endocrine glands as you do. She even secretes all the hormones that you do. However, due to growth of tiny tumors in her endocrine glands, she may secrete too much of one kind of hormone and not enough of another. Her body is under constant stress, and her negative feedback mechanisms do not restore homeostasis. Instead, positive feedback results and she becomes ill due to the over secretion of hormones putting constant stress on her body.

Going Beyond

Melatonin is a hormone that is produced by the tiny pineal gland located within the brain, and it is involved in your sleep and awake cycle. Many people experience tiredness, inability to concentrate, and irritability when they are not exposed to periods of sunshine. Read “Light up Your Life!” on p. 443 of your textbook and address the following two questions:

1. Explain why people living in northern countries such as Canada, parts of Russia, and the Scandinavian countries may be more susceptible to Season Affective Disorder (SAD), as compared to people who live in more southern regions.
2. How do innovative technologies such as the “Litebook” contribute to society

Lesson Summary

In this lesson, you investigated the following focusing question:

• How is the endocrine system organized, and how do its parts communicate with each other and with various parts of the body?

To answer this question, the major glands of the endocrine system including the hypothalamus/pituitary complex, the thyroid gland, the parathyroid glands, the adrenal glands, and the islet cells of the pancreas were introduced and studied. These glands secrete hormones which have unique effects on the body by interacting with target cells. Some of these hormones work opposite each other and are called antagonistic hormones. Other hormones, called tropic hormones, target other endocrine gland, causing them to consequently secrete more hormones. Levels of hormonal secretions are regulated by negative feedback mechanisms. Negative feedback tends to stabilize a system because the response compensates for the change in the internal environment. This leads to the reestablishment of homeostasis. Reinforcing the change in the internal environment leads to instability and an imbalance or deviation from homeostasis called positive feedback. It is rarely beneficial in the body.

Glossary

antagonistic hormones: two hormones that produce opposite effects

endocrine gland: a cell, tissue, or organ that produces secretions that are released directly into the bloodstream; ductless gland e.g. thyroid gland
exocrine gland: a cell, tissue, or organ that produces secretions that are released through ducts or channels; e.g. a sweat gland

gonadotropic hormones: hormones that affect the reproductive organs; also called the gonads

homeostasis: the maintenance of a constant internal environment or one within narrow limits despite possible fluctuations in the external environment

hormone: a chemical messenger that is produced by specialized cells, circulated in the bloodstream, and coordinates the various parts of the body by interacting with target cells

lipid soluble hormones: hormones that are chemically identified as lipids or steroids, such as testosterone, estrogen, progesterone, or cortisol
negative feedback: a mechanism where deviation from the optimum state causes a return to the optimum state; acts to eliminate any deviation from optimal conditions and leads to stability
positive feedback: a mechanism where movement away from the optimum state causes further deviation from the optimum state; usually leads to instability and is tolerated by the body only for a short time
set point (set value): ideal or optimum conditions

tropic hormone: a hormone that has another endocrine gland as its target cell

water soluble hormones: hormones that are chemically identified as being either amino acids or proteins, such as epinephrine, human growth hormone, thyroxine, insulin, and glucagon

Lesson 1.2.2

Lesson 2—Who is in Charge?

Get Focused

In the first lesson of this module you learned about the different glands that make up the endocrine system. The level of hormones from these different glands circulating in the body needs to be just right. Like the brain in the nervous system, the endocrine system also has a boss to ensure homeostasis. The kingpin of the operation is the hypothalamus/pituitary gland complex. From your previous studies, you should recall that the hypothalamus is part of the brain, making this is one of the situations where the nervous and endocrine systems overlap. You may know the pituitary as the gland that regulates cellular respiration or metabolism from your studies in Biology 20. If this complex were not doing its job your life would quickly unravel. You would not be able to function or develop normally. Your growth might be stunted, and your voice change would never occur if you were a boy. In Emily’s case, tiny tumors in her pituitary gland either cause an oversecretion or an undersecretion of several pituitary hormones that regulate other endocrine glands. Inappropriately stimulated, these glands, in turn, oversecrete or undersecrete their hormones and cause potentially life threatening symptoms.

In this lesson you will explore the following focusing question:

• Who is the boss of the endocrine system and how is the control of the endocrine system managed?

This lesson will take approximately 2 hours to complete.

Module 2: Lesson 2 Assignment (not to be submitted.)

While you are completing this lesson, there will be many opportunities for you to learn, understand and practice the concepts that are presented. After completing these assignments, as well as your summary notes, file everything in your course folder for reference when you are preparing for unit exams and the Diploma exam.

Remember, you also have the option of trying additional questions from the textbook for further practice. Consult with your instructor for answers to these questions. “The Key” will provide you with many Diploma exam style multiple choice, numerical response, and written response questions that will be an excellent review of the module, as well as good preparation for the Diploma exam.

There is no assignment for this lesson but you should watch the tutorial video for this lesson and submit a summary.  Bio30 tut#1.2.2 Metabolism

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all of the questions and place those answers in your course folder.

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The Posterior Pituitary

You have learned that the hypothalamus lies just above the tiny, pea-sized pituitary gland in the middle of the head. The two structures are connected by a stalk. Anatomically, the pituitary gland is made up of two very different kinds of cells. The posterior pituitary is made up of modified nerve cells. It is connected to the hypothalamus by neurosecretory cells in the stalk, which secrete two hormones – antidiuretic hormone (ADH, also called vasopressin) and oxytocin. Releasing hormones (releasing factors) from the hypothalamus signal the release of the stored ADH and oxytocin from the posterior pituitary into the blood stream.

You have already learned that ADH targets cells in the kidney to reabsorb more water into the blood producing a smaller volume of concentrated urine. You have also practiced drawing the negative feedback loop that regulates ADH production in Lesson 1. If ADH cannot be produced or secreted, then copious amounts of urine are produced (up to 24 L/24 h). The person experiences what is known as diabetes insipidus (diabetes meaning to pass through and insipidus meaning without taste) which is treated with ADH in pill form.

Oxytocin, the other hormone secreted by the hypothalamus and released by the posterior pituitary begins the contractions of the uterine muscles at the end of pregnancy, thus initiating childbirth. It also causes tiny cells that surround the milk glands in the breasts to contract and squeeze milk into the nipples. You will study oxytocin in more detail in Unit B.

Watch and Listen

To review and further your understanding of the hormones associated with the posterior pituitary you can watch the following video segments:

The Pituitary

Oxytocin

Oxytocin and child birth

Antidiuretic Hormone

Try This

TR 1.

To further your understanding and application of concepts on posterior pituitary hormones, complete the following questions. Answer in full sentences where appropriate. After checking your work, file it in your course folder.

1. In general, how is a hormone able to recognize and stimulate its target cells?
2. Describe how the secretion of ADH is regulated by negative feedback. 
3. What causes diabetes insipidus? Describe the symptoms of this condition.
4. Complete the following table:

Self-Check Answers

1. A hormone is able to recognize its target cells because the target cells have receptors on their cell membrane that have a complementary shape to the shape of the hormone molecules. When the hormone fits into the receptors, the cells are stimulated by the hormone.
2. When the solute/osmotic concentration of the blood increases, tiny receptors called osmoreceptors in the hypothalamus are stimulated. In turn, neurosecretory cells in the hypothalamus are stimulated to secrete ADH, which moves along the axons of the neurosecretory cells into the posterior pituitary and is released into the blood stream. ADH moves in the blood to the kidneys where it fits into receptors on the kidney tubules. This causes the tubules to become more permeable and reabsorb more water into the blood, which in turn reduces the urine volume. The increased water in the blood reduces the solute/osmotic concentration, which inhibits the osmoreceptors, and less ADH is released. Students may include a diagram of a feedback loop as shown below.

3. Diabetes insipidus is usually caused by a tumor which prevents the hypothalamus from producing ADH, or prevents the posterior pituitary from releasing the ADH. Consequently, the kidney tubules cannot reabsorb adequate amounts of water, which in turn increases the urine output. The main symptom of diabetes insipidus is a very large output of urine with the other components of urine remaining stable.
4. The completed table should resemble the following:

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Anterior Pituitary

Compared to the posterior pituitary which only stores and releases hormones produced in the hypothalamus, the anterior pituitary synthesizes and releases 6 major hormones. It is connected to the hypothalamus by blood vessels that run through the stalk. Three of the hormones (FSH, LH, and prolactin) are involved in the reproductive process and will be studied in detail in the next unit. For this unit you will learn their general functions. The other three hormones –adrenocorticotropic hormone (ACTH), thyroid stimulating hormone (TSH), and human growth hormone (hGH), – will be introduced in this lesson. The hypothalamus and pituitary control their production and release through negative feedback loops. The hypothalamus is stimulated to secrete releasing hormones by conditions in the internal environment of the body. Moving through the blood vessels in the stalk, the releasing hormones stimulate target cells in the anterior pituitary, which produces ACTH, TSH, and hGH. As indicated by its name, ACTH stimulates the outside layer of the adrenal gland called the adrenal cortex, which releases cortisol, a major stress hormone, and aldosterone. TSH stimulates the thyroid gland and its production of thyroxine. Emily’s anterior pituitary gland overproduces ACTH and under secretes TSH. You will study the effects of inappropriate amounts of these hormones on the body in the next two lessons.

Releasing hormones ACTH, TSH, and hGH, which are produced in the hypothalamus, are called tropic hormones. In the Lesson 1 you learned that tropic hormones are one group of hormones. Do you remember their characteristics? Explore this group of hormones in more depth by studying Figure 13.10 on page 441. Read, and summarize the section on tropic hormones on pages 441 – 442. Store your notes in your course folder.

Watch and Listen

You can review some of the concepts on the anterior pituitary by watching the following video

Anterior Pituitary

Try This

TR 3.

To practice applying your knowledge on specific tropic hormones and their regulation by the hypothalamus and anterior pituitary gland complete the questions below. Check your work and add it to your course folder.

1. Using ACTH as an example, explain a tropic hormone. Besides ACTH, identify three other tropic hormones.

Using the following flowchart which illustrates regulation by tropic hormones, answer the next 6 questions.

2. How is the secretion of tropic hormones from the pituitary gland regulated?
3. If Hormone 2 in the tropic hormone pathway is TSH, what is the target gland?
4. If Hormone 2 is TSH, what is Hormone 3?
5. Explain how Hormone 3 can inhibit or stimulate the release of Hormone 1, and inhibit release of Hormone 2?
6. If the target gland is the adrenal cortex, identify the specific tropic hormone at work.
7. Identify Hormone 3 produced by the adrenal cortex.
8. Explain how the anterior and posterior pituitary differ, with respect to their relationship to the hypothalamus.
9. Explain how the differences between the 2 regions of the pituitary relate to the nature of their hormonal secretions.
10. Suppose a scientist has discovered a new hormone. It is not clear what gland produces the hormone, but people who produce above average amounts of this hormone also produce very high levels of insulin. Based on your knowledge of how tropic hormones function, provide a possible explanation for the observation.

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Human Growth Hormone

The anterior pituitary regulates growth, muscle development, and fat metabolism through the production of human growth hormone (hGH), which ultimately affects every part of your body. Athletes are interested in using human growth hormone to improve performance because it stimulates protein synthesis and subsequent muscle development as well as toning of muscles. Overweight people are interested in using this hormone to fight obesity because it inhibits storage of fat and encourages its use for cellular respiration. At the same time hGH inhibits use of carbohydrates such as glucose. Older people are also interested in using hGH. As one ages, the levels of this hormone decrease - fat is harder to keep off and muscles become flabby. Testimonials, by aging stars, such as Sylvester Stallone, are prominent in advertisements for hGH. You will examine some of these ideas in the Thought Lab further in this lesson.

Nearly everyone is interested being tall. Girls usually imagine being swept away by a hero who is “tall, dark, and handsome”. Human growth hormone stimulates the growth plates at the end of the long bones and causes these bones to lengthen and increase a person’s height. Too much hGH during childhood causes gigantism. Today, Leonid Stadnyk is the tallest living person at a height of 2.57 m or 8 feet 5.5 inches. Too little hGH during childhood results in pituitary dwarfism. Thapa Magar, the shortest living person is only 50.8 cm or 20 inches tall. Emily, who you met earlier, had some minute tumors develop in the anterior pituitary several years after her final growth spurt. Instead of gigantism, she shows the symptoms of acromegaly. Because her growth plates have sealed, she cannot grow in height. Instead, her jaw has thickened, as have her ribs, and her fingers, toes, and nose have become enlarged.

Read

To learn more about human growth hormone and to summarize the functions and effects of this important hormone read pages 444 – 446 in your textbook. Figures 13.11 and 13.15 are good summaries that you may want to include in your course folder along with your notes.

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Try This

TR 4.

Emily’s husband had become very concerned about some of the symptoms that she had been exhibiting and the inability of several physicians to diagnose and treat whatever was wrong. Finally a doctor figured out what was wrong but only provided Emily and her husband with limited information. Her husband thus decided to write to a newspaper column that specializes in answering questions about health.

Pretend that you are Dr. Stoppain, who answers health-related questions in a daily newspaper column. You received the following letter, and your task is to write a response by defining the health condition, explaining the symptoms of the condition, outlining possible treatment, and answering the writer’s questions.

Dear Dr. Stoppain,

My wife is 30 years old. For the last several years she has suffered from numerous violent headaches. She has sought help from several different doctors who suggested various treatments. None of these worked. Then she noticed that her vision was blurred, particularly off to the sides. She went to see an eye doctor who suggested that she had acromegaly and referred her to an endocrine specialist who confirmed the suspicion. We know next to nothing about this condition. What causes it? Is treatment successful? Will acomegaly shorten her life?

Concerned Husband

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Thought Lab

Evaluating Potential Uses for Human Growth Hormone

Parents want their children to be successful. Recent studies have linked job success with being tall. In China, certain heights have been used as a prerequisite for jobs. Since 1985, genetic engineering technology has been used to produce human growth hormone, referred to as synthetic human growth hormone. Parents have pestered doctors to prescribe it for the purpose of increasing the stature of their children. In addition, it has been discovered that human growth hormone may have some antiaging properties. The internet is littered with ads for its purchase.

Since the approval of the restricted use of synthetic hGH, concerns have arisen about its use and potential abuse. Health Canada has approved extremely limited use of the hormone, which is very expensive (Injections cost in excess of $25 000 per year.) and may be associated with several negative health effects.

Problem

Should Health Canada approve the widespread use of synthetic hGH for Canadians?

© Konstantin Sutyagin/shutterstock

Issue 1

Until recently, the use of synthetic hGH was approved only for those children who had malfunctioning pituitary glands and could not produce adequate amounts of the necessary hormone themselves. Recently, the use of synthetic hGH has been approved for children who are genetically of short stature. Should people have the option to take synthetic hGH just to increase their genetically predetermined height?

© Glenda M. Powers/shutterstock

Issue 2

In adults, the production of natural hGH declines with age. This makes it increasingly difficult to reduce one’s body fat as one ages. Given that obesity has reached epidemic levels in the North American population, and one of the functions of hGH in the body is to reduce cellular fat, should synthetic hGH be approved as a diet treatment for obesity?

© Carlos E. Santa Maria/shutterstock

Issue 3

Because one of the functions of hGH in the body is to build lean muscle mass, its use has become widespread among various athletes. In fact, many athletes at the 1996 summer Olympic Games in Altlanta, Georgia, referred to the event as the “hGH Games.” Despite its expense, many athletes, from baseball players to weightlifters, are acquiring synthetic hGH because it is difficult for drug testers to detect. Should competitive athletes be allowed legal access to synthetic hGH?

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Reflect and Connect

So, who is in charge of the endocrine system? Is it the hypothalamus, the pituitary gland or both? To review the connections between the hypothalamus and the pituitary gland watch the following video

Relationship between the Hypothalamus and the Pituitary Gland

Then, using what you have learned in this lesson about the hypothalamus, the posterior, and the anterior pituitary, choose who you think is the boss of the endocrine system and provide as much evidence as you can to support your position. You may choose the hypothalamus, the posterior pituitary, anterior pituitary or a combination of these structures. You may wish to discuss your ideas with your instructor or post your position and evidence on the discussion board for your peers to evaluate. Read at least two other students’ positions and discuss their evidence.

Self Check

Review the lesson, then complete the following multiple choice questions which will help assess your understanding of the concepts presented in this lesson. Check your answers and discuss any questions that you do not understand with your instructor.

Use the following diagram to answer the next two questions.

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), 445, fig. 13. 12. Reproduced by permission.

1. The structures labeled A and F on this diagram respectively are the
   
   
   1. hypothalamus and posterior pituitary.
   2. hypothalamus and anterior pituitary.
   3. anterior pituitary and posterior pituitary.
   4. posterior pituitary and anterior pituitary

2. The function of the structure labeled C on the diagram is to
   
   
   1. synthesize antidiuretic hormone and oxytocin.
   2. stimulate release of ADH and oxytocin.
   3. stimulate production of tropic hormones
   4. regulate the levels of ADH released into the blood.

Use the following diagram to answer the next two questions.

3. Which endocrine gland shown on this diagram would be directly responsible for the development of dwarfism or gigantism in humans?
   
   
   1. G
   2. F
   3. B
   4. D

4. Which of the following best explains the development of acromegaly in adults?
   
   
   1. increased production of TSH
   2. increased production of ACTH
   3. increased production of ADH
   4. increased production of hGH

Use the following feedback loop and information to answer the next two questions.

For this question, assume that the feedback loop shown is for a hormone primarily responsible for regulating the metabolic rate. The target cells for this hormone are all the cells of the body which it stimulates to metabolize at a faster rate.

5. Which row correctly identifies the hormones indicated by the numbers 1. 2, and 3 on the feedback loop?

6. The number 5 on the diagram would cause the release of the following hormone:
   
   
   1. releasing hormone
   2. inhibiting hormone
   3. ACTH
   4. TSH

7. The pituitary is often called the “master gland” because it
   
   
   1. receives impulses directly from the brain
   2. controls every other gland and organ in the body
   3. secretes hormones that control the functions of exocrine glands
   4. produces hormones that regulate the activities of other endocrine glands

8. An abnormally large volume of urine may be produced after a person drinks alcoholic beverages. It is likely that ethyl alcohol affects normal secretion of
   
   
   1. antidiuretic hormone
   2. thyroxine
   3. cortisol
   4. aldosterone

Use the following information to answer the next question.

The following procedures and observations were used to determine the function of secretions from an animal organ suspected of being an endocrine gland.

The suspected endocrine gland was surgically removed from the animal.
Symptoms in the animal were observed.
A chemical mixture was extracted from the suspected endocrine gland.
The chemical mixture was injected into the animal.
Symptoms in the animal were no longer observed.

Normal female rats injected with the chemical mixture showed accelerated body growth and increased thyroxine production.

9. Based on these observations, the organ was the
   
   
   1. thyroid gland
   2. posterior pituitary
   3. hypothalamus
   4. anterior pituitary

Use the following information to answer the next question.

10. If Gland 1 is the pituitary gland, the row that identifies Hormone 1, Gland 2, and Hormone 2 is

Use the following information to answer the next question.

11. Normally inhibition of the pituitary gland would occur if the secretion of Hormone X
    
    
    1. increased, causing a decrease in the secretion of Hormone Y
    2. decreased, causing a decrease in the secretion of Hormone Y
    3. increased, causing an increase in the secretion of Hormone Y
    4. decreased, causing an increase in the secretion of Hormone Y

Reflect on the Big Picture

The endocrine system is self-regulating through its boss and through negative feedback mechanisms. What happens when the CEO or boss of the endocrine system is not doing its job, as in Emily’s case? How are the regulatory pathways affected when tropic hormones are AWOL [absent with-out leave]? In Lesson 3 you will examine Emily’s inability to regulate the stress hormones produced by the adrenal gland because her pituitary tumor causes too much ACTH to be secreted. In Lesson 4 you will examine the effects of her body not being able to regulate the thyroid hormone thyroxine because the tumor causes the under secretion of TSH.

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Lesson Summary

Self-regulated by the hypothalamus/pituitary complex, the endocrine system utilizes tropic hormones such as releasing hormone from the hypothalamus and ACTH, TSH, and hGH from the anterior pituitary to stimulate other endocrine glands, such as the adrenal gland and thyroid gland, to produce their hormones. Negative feedback shuts off the tropic hormones when levels of hormones by the target glands reach correct amounts. Disruption in the level of a hormone can cause serious effects on physiological function such as urine production, growth, and metabolic rate.

Lesson Glossary

acromegaly: a condition brought about by excessive secretion of human growth hormone in an adult; hands, feet and nose widen and become enlarged, jaw protrudes, voice becomes husky, barrel chest may develop, sweat glands enlarge, heart enlarges, high blood pressure may develop, enlarged tissues press on nerves, especially the optic nerves causing loss of vision, particularly in the outer fields, and pressure on the brain causes severe headaches; there is an increased likelihood of developing diabetes mellitus

anterior pituitary: an endocrine gland consisting of secretory cells which synthesize and secrete several hormones directly into the bloodstream

diabetes insipidus: a condition caused by lack of ADH which results in excessive production of very dilute urine; ADH may be produced in insufficient quantities by the hypothalamus or the posterior pituitary may fail to release it into the bloodstream when a tumor develops

gigantism: a condition where a person produces excess hGH during childhood, resulting in a height of 8 feet or more

hypothalamus: region of the brain located below the cerebral hemispheres and thalamus, and just above the pituitary gland; functions in maintaining homeostasis, and is especially important in coordinating the endocrine and nervous systems; secretes hormones of the posterior pituitary as well as releasing hormones which regulate the anterior pituitary

neurosecretory cells: specialized nerve cells in the hypothalamus that extend into the posterior pituitary and secrete ADH and oxytocin into the posterior pituitary and subsequently into the bloodstream

pituitary dwarfism: a condition where a person does not produce enough hGH during childhood resulting in short stature

posterior pituitary: an extension of the hypothalamus composed of nervous tissue that secretes hormones produced in the hypothalamus into the bloodstream; consists of a temporary storage site for hormones produced in the hypothalamus

releasing hormones: sometimes called releasing factors; hormones produced by neurosecretory cells in the hypothalamus that stimulate or inhibit the secretion of hormones by the anterior pituitary

tropic hormones: chemical messengers (hormones) that have another endocrine gland as their target; hormones that stimulate other glands to produce their secretions

vasopressin: also called antidiuretic hormone

Lesson 1.2.3

Lesson 3—The Adrenal Gland

Get Focused

When you studied the sympathetic nervous system in Module 1, you learned about the “flight or fight” reaction, which refers to the tendency in stressful situations to run away or stay and work through the situation. Imagine watching a horror movie and anticipating the feeling of being scared out of your skin. If your life were a horror movie, you would constantly be on edge—anxious and just waiting to be scared. Life would be a constant adrenaline rush. How long do you think you could last like that?? Emily’s life is like a never-ending horror movie. Tiny tumors in and on her adrenal glands cause the glands to overproduce epinephrine, norepinephrine and cortisol—hormones that combat stress both short and long term. As a result, Emily’s body, left untreated, prepares itself for the flight or fight reaction twenty-four seven.

In this lesson you will explore the following focusing question:

How do the adrenal glands and their secretions affect the body?

This lesson will take approximately 2.0 – 2.5 hours to complete.

Module 2 Lesson 3: Assignments

  Once you have completed all of the learning activities in this lesson, you can complete the online assignment.

Bio30 1.2.3 online assignment

You must decide what to do with the questions that are not marked by the teacher.

You should also watch the tutorial video for this lesson and submit a summary. Bio30 tut#1.2.3 Stress Response

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all of the questions and place those answers in your course folder.

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Explore

Read

Adrenal Gland and Stress Reactions

Like small baseball caps, the adrenal glands perch on top of the kidneys. See page 451 of the text. Further examination shows that each adrenal gland is really two glands with the adrenal cortex (meaning bark) wrapped around the adrenal medulla (meaning middle). The adrenal cortex consists of layers of secretory cells while the adrenal medulla consists of modified nerve cells. What other gland have you studied that is made of both nervous and endocrine tissue? Both parts of the adrenal gland produce and release hormones in response to stress stimuli. Remember the Student Stress! Lab that you completed in Lesson 1 and the stress that the experimenter created in the subjects? The adrenal gland would have played a significant role in bringing about changes in the subjects blood pressure and heart rate. The stress reactions of the human body comprise a wide range of reactions which prepare the body to resist any damaging or potentially damaging changes in the environment. A great variety of stimuli trigger these responses, including injury, infection and emotional responses such as fear or anger. The effectiveness of a particular stimulus varies from person to person. You may be freaking out about that exam in the afternoon but your friend may not be worried about it at all. Or the bass in your car stereo may be driving your parents nuts, but you’re enjoying the beat.

Watch and Listen

At this time, you may want to review and reinforce concepts about the adrenal gland and stress responses by viewing the video below.

Adrenal Glands

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Read

The Adrenal Medulla

In Module 1, you studied sympathetic nerve activity, which is collectively called the “fight or flight” responses. These responses prepare the body for immediate action. To refresh your memory and summarize what these responses are, read the following two pages of your text: page 397 and page 452.

Nerve impulses from the sympathetic nerve system stimulate the adrenal medulla to release epinephrine and norepinephrine. These hormones circulate in the bloodstream and enhance the activities of the sympathetic nervous system. Together the sympathetic nervous system and the release of hormones from the adrenal medulla provide the resources (oxygen and blood glucose) for energy release by aerobic cellular respiration and allow the body to perform far beyond its capacity. You may have heard stories of how a mother fearlessly fought off a bear which was mauling her child, or a man lifting a car to free an accident victim pinned beneath it. These incredible feats were performed because the sympathetic nervous system stimulated the adrenal medulla to release a burst of adrenaline which enabled a lot of energy to be released by metabolism.

© John Bell/shutterstock

Watch and Listen

The following videos will reinforce your understanding of how the adrenal medulla works to combat the effects of what is sometimes called short term stress.

Epinephrine Release

Body’s Responses Norepinephrine

Symptoms of Stress

Try This

TR 1.

To review the concepts on the short term stress response, complete the following questions. After checking your answers, file them in your course folder.

1. Describe a “fight” and a “flight” response and include the biological mechanism behind these responses.

2. Identify three groups of stress stimuli (categories of things that cause stress).

3. Explain how the hypothalamus is involved in the release of epinephrine and norepinephrine by the adrenal medulla. You may choose to use a flow chart to illustrate your response.

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The Adrenal Cortex

Cortisol produced by the adrenal cortex is thought to be the most important glucocorticoid in humans. It is primarily concerned with glucose metabolism during periods of long term stress, such as engaging in athletic competition and writing Diploma exams. It also plays a role in helping to maintain high blood pressure. It works in concert with the sympathetic nervous system and the release of epinephrine and norepinephrine by the adrenal medulla. After a time, the stress responses fade and normal conditions are restored in part by the parasympathetic nervous system, as you experienced in the Student Stress! Lab. However, if stress producing stimuli persist, the body may be subjected to an excessively high metabolic rate, high blood pressure, and an elevated heart rate for a prolonged period of time. This is particularly damaging for the circulatory system and is a contributing factor in increasing the risk of heart attacks and atherosclerosis, which you studied in Biology 20.

Cortisol also acts to suppress inflammation, and is sometimes used in the treatment of arthritis and allergies. Side effects, such as reducing the effectiveness of your immune system, limit its usefulness.

You can further your understanding of the role that cortisol plays in body homeostasis by reading pages 452 – 453 of your textbook and making notes.  Remember to file your notes in your course folder.

Or if you prefer, you may watch the following videos and make some notes for your course folder.

Adrenal Cortex

Cortisol is secreted in response to ACTH when the anterior pituitary is stimulated by releasing hormone from the hypothalamus. Secretion is decreased by negative feedback exerted on the anterior pituitary and the hypothalamus as outlined in the general regulatory pathway of tropic hormones in Figure 13.10 on page 441 of your textbook, and in the following video.

Adrenocorticotropic Hormone

Try This

TR 2.

Use the following information to answer the next four questions. Where appropriate, practice answering in complete sentences. After checking your answers, file them in your course folder. Consult with your instructor for clarification if you do not understand any questions/answers.

Due to tiny tumors growing in Emily’s anterior pituitary, she over-produces ACTH which in turn stimulates over-secretion of cortisol. The cortisol maintains a high metabolic rate by burning protein and fat, constricts her blood vessels, causing an increase in her blood pressure, and causes her heart to race constantly.

1. Draw a feedback loop that would illustrate this disruption in Emily’s production of cortisol.

2. Before treatment, Emily’s blood glucose was abnormally high. Explain how this situation could have been the result of overproduction of cortisol.

3. Emily’s heart rate and blood pressure were elevated around the clock. Explain why this is a potentially life-threatening situation.

4. Emily was very prone to infections such as colds, laryngitis, and bronchitis. Explain why this was probably the result of elevated cortisol levels.

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Aldosterone

A second group of hormones produced by the adrenal cortex are called the mineral corticoids, which includes aldosterone. Read page 454 in your textbook and summarize the role that aldosterone plays in homeostasis. File your summary in your course folder for later reference.

Try This

TR 3.

To apply your understanding of how aldosterone contributes to sodium ion and water homeostasis, complete the following questions using full sentences.  Autocheck your answers. Consult with your instructor if you are having difficulty understanding the questions. File your work.

1. What is the difference in the way that aldosterone and ADH affect water balance?

2. Why are sodium ions important in the body?

3. How does aldosterone help the body cope with an ongoing stressful situation?  How is this response different from the “fight or flight” response?

Self-Check

Complete the following Self Check in preparation for doing the lesson assessment that follows. This Self Check consists of both multiple choice and written response style questions. When you have finished, check your answers, and if you do not understand any of the concepts be sure to discuss this with your instructor.

Use the following information to answer the next two questions.

 n

Use the following additional information to answer the next question.

1.  A logical interpretation of the graph is that the

a) secretion of cortisol is inhibited by increased ACTH

b) secretion of cortisol is doubled if the secretion of ACTH is doubled

c)  adrenal glands respond more quickly to small amounts of ACTH than to large amounts of ACTH

d)  adrenal glands respond to large amounts of ACTH by having a maximum cortisol secretion rate

2. The secretion of Hormone A causes an increase in activity X in the body. If this mechanism works by positive feedback, which of the following statements represents this?

a)An increase in X produces an increase in A

b)  An increase in A produces a decrease in X

c)  An increase in X produces a decrease in A

d)  A decrease in A produces an increase in X

3.  Suppose you are lost in concentration while studying biology. Suddenly, the phone rings and startles you. Outline the physiological changes that occur in your body due to release of the stress hormones cortisol and epinephrine. What triggers the release of each of these hormones?

4.  The appropriate level of hormones circulating in the body is critical to proper homeostasis. Too much cortisol and aldosterone and a person develops Cushing’s Disease. Too little of these hormones and a person develops Addison’s Disease. Complete the following table contrasting the two disorders.

Contrasting Oversecretion and Undersecretion of Adrenal Cortex Hormones

9. Features	Cushing’s Disease	Addison’s Disease
   Hormones Involved
   Level of Hormones Secreted
   Cause of Inappropriate Level of Secretion
   Symptoms
   Treatment

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Reflect and Connect

Stress in moderate doses is a good thing! How is it good? What kinds of activities are carried out better under some stress? Do you think that athletes would do as well as they do if they did not experience the stress of competition that gives them that extra burst of epinephrine? If your heart did not beat a little faster and your breathing rate was not increased at all, do you think you would do as well on an exam? Why do you think “extreme sports” are becoming so popular? Is being too laid back a good thing in some situations? How is too much stress bad for you? Why does a constant accelerated heart rate and constant higher than normal blood pressure lead to heart attacks?

Going Beyond

Hans Selye, a scientist at the University of Montreal, first described the General Adaptation Syndrome or GAS. GAS has three main stages: Alarm, Resistance, and Exhaustion. However, Selye did not regard all stress as bad and even said that some stress was the “spice of life”. Researchers have called this good stress “eustress”. Using library sources as well as the internet, research more about GAS.

Lesson Summary

In this lesson, the following focusing question was explored:

How do the adrenal glands and their secretions affect the body?

Located atop the kidneys, the adrenal gland is really two glands. Similar to the two lobes of the pituitary gland, the adrenal cortex is composed of several layers of secretory cells, while the adrenal medulla is made up of modified nerve cells. Hormones from both parts of the adrenal gland deal with stress. Epinephrine and norepinephrine from the adrenal medulla intensify the “fight or flight” responses of the sympathetic nervous system. The purpose of these responses is to get more oxygen and glucose to the tissues. For example, breathing rate increases and bronchioles dilate so more oxygen can be taken to the lungs. Glucose is synthesized from glycogen. Heart rate, cardiac output and blood pressure are increased so that the increased levels of oxygen and glucose can be delivered to the muscles. Cortisol, from the adrenal cortex, intensifies the fight or flight responses. It increases blood glucose by converting amino acids, proteins, and fats into glucose. Cortisol also decreases the inflammatory response, so it is useful in treating allergic reactions and joint inflammations. High levels of cortisol are regulated by negative feedback on the hypothalamus and anterior pituitary, and their secretions of releasing hormone and ACTH respectively. Aldosterone, another hormone from the adrenal cortex, is concerned with regulation of sodium ions and subsequent homeostasis of tissue water.

Glossary

adrenal medulla: the central or middle part of the adrenal gland composed of modified nervous tissue which responds to sympathetic nerve signals by secreting the “fight or flight” hormones epinephrine and norepinephrine in reaction to stress

adrenal cortex: the outer portion of the adrenal gland composed of three distinct layers of cells which respond to hormonal signals from the anterior pituitary by producing three groups of hormones including the glucocorticoids and mineralocorticoids; reacts to stress stimuli and affects salt and water balance

glucocorticoids: a group of hormones, produced by the adrenal cortex, of which cortisol is of prime importance; influences glucose metabolism from protein and fat and immune function by suppressing inflammation

mineralocorticoid: a hormone produced by the adrenal cortex that regulates salt and water homeostasis by influencing the reabsorption of sodium ions

fight or flight response: a collection of responses that prepare the body to combat an immediate stressful situation by increasing the availability of oxygen and glucose for aerobic cellular respiration which releases energy; short term stress responses that ensure increased amounts of glucose and oxygen available to muscle cells for cellular respiration, which results in increased available energy for use by muscles
 
cortisol: also called hydrocortisone or cortisone; cortisol is secreted in highest amounts in humans and is produced by the adrenal cortex in response to stimulation by ACTH; involved in enhancing short term stress responses and in stimulating conversion of protein and fat into glucose

aldosterone: hormone produced by adrenal cortex in response to an increase in certain enzymes and high levels of ACTH; acts to increase sodium ion reabsorption

epinephrine: a hormone produced by the adrenal medulla in response to stress; also called adrenaline; the adrenal gland produces about 80% epinephrine and 20% norepinephrine

norepinephrine: a second hormone produced by the adrenal medulla in response to stress but in much smaller quantities; about 20% of adrenal medulla secretions are norepinephrine

long term stress responses: responses, mainly stimulated by cortisol, which are of long duration

Lesson 1.2.4

Lesson 4—The Thyroid and Parathyroid Glands

Get Focused

Hyperthyroidism and hypothyroidism are two opposite types of thyroid disorders. If you have hyperthyroidism you might always feel too hot, experience weight loss, and find it difficult to concentrate. You may also be jittery and hyperactive. If you have hypothyroidism, you are likely to feel cold, you may be overweight, you may feel lethargic, and you may have trouble staying awake. Emily developed hypothyroidism. She also developed tiny growths in the parathyroid glands. An overproduction of a parathyroid hormone caused her to lose calcium from her bones, which became fragile and brittle and caused her to develop kidney stones.

In this lesson you will explore the following focusing question:

• How do the thyroid and parathyroid glands contribute to homeostasis?

This lesson will take approximately 2.0 – 2.5 hours to complete.

Module 2: Lesson 4 Assignment

  After you have completed all of the learning activities for this lesson, you can complete the online assignment.

Bio30 1.2.4 online assignment.

You should also watch the tutorial video for this lesson and submit a summary.  Bio20 tut#1.2.3 Thyroid Parathyroid

You must decide what to do with the questions that are not marked by the teacher.

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course.  You should respond to all of the questions and place those answers in your personal course folder to be used for study purposes.

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Anatomy of the Thyroid Gland

The structure of the thyroid gland is different from other endocrine glands. Thyroid tissue contains many spherical follicles consisting of a single layer of secretory cells surrounding a storage space. The secretory cells produce a precursor of thyroxine which is stored in the storage space. Stimulation by thyroid stimulating hormone, produced by the anterior pituitary, causes the follicles to change the precursor and release it as thyroxine into the many blood capillaries between the follicles. Look at the micrograph of thyroid tissue. Notice that between the follicles there are some large cells (C cells or parafollicular cells). These cells secrete calcitonin, another important thyroid hormone which will be addressed later in this lesson.

Read pp. 446 – 447 on the structure of the thyroid gland; study Figure 13.16 on p. 448, and then complete Try This #1.

Try This

TR 1.

On the Thyroid Tissue Handout, label the follicle, storage space, C cells and the blood capillaries (vessels). Annotate the diagram by indicating the function of each structure in brackets after the name label. Once you have finished, check your diagram and annotations and place it in your course folder.

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The Thyroid Gland and Metabolism

Do you know someone who seems to be able to consume great amounts of food and still stay thin? Do you know other people who seem to put on weight just by smelling or looking at food? Thin people often excuse themselves by explaining that they have a high metabolism. Metabolic rate is regulated by the hypothalamus/pituitary complex, which produces tropic hormones that stimulate the thyroid gland to release increased amounts of thyroxine. Thyroxine increases the number of mitochondria in cells and generally increases cellular respiration, a major set of decomposition chemical reactions that make up metabolism. You may wish to review these concepts from Biology 20.

To gain an understanding of the composition of thyroxine, how it is regulated, what functions it performs, and what happens when it is over-secreted or under-secreted, answer the following questions in Try This #2. The completed answers to these questions can become your notes for this lesson so it is important to answer in complete sentences. To help you answer the questions, you may use library sources, the internet, pp. 446 – 448 in your textbook, or the video segments which are listed below.

Negative Feedback Loop: Thyroxine

Try This

TR 2.

After completing the questions in this exercise, check your answers and file your work in your course folder. If you do not understand any of the concepts, consult with your instructor for clarification.

Use the following information to answer the questions that follow.

Usually people who have FMEN1 do not develop tumors in the thyroid gland, and Emily did not have a thyroid tumor. However, in Lesson 2 and 3, you learned that Emily had tiny tumors in her anterior pituitary which affected the tropic regulatory pathway for ACTH by causing the over-secretion of this hormone. Those tumors have also affected the secretion of thyroid stimulating hormone (TSH) by causing an under-secretion of this regulatory hormone.

1. Draw a feedback loop that would illustrate the proper negative feedback regulation on the production of thyroxine.
2. Explain how Emily’s feedback loop would be different from the one you drew in Question #1.
3. Identify the element that is necessary for the synthesis of thyroxine. Although we may live in a zone where this element is in short supply in the soil and water, we are able to produce a fully functioning thyroxine. Explain why.
4. Outline the functions of thyroxine in both children and adults.
5. Emily’s feedback mechanism was not working and she could not produce adequate amounts of thyroxine. Identify Emily’s resulting thyroid disorder.
6. Describe the symptoms that Emily would exhibit as a result of a lack of thyroxine. Outline a treatment that is possible for Emily.
7. Define goiter. Left untreated, do you think Emily could have developed a goiter? Explain why or why not.
8. Outline the results of under-secretion of thyroxine in newborn babies. Identify this disorder.
9. 
   © Carolina K. Smith, M.D./shutterstock
   Due to the anterior pituitary tumor, Emily could have just as easily over-secreted thyroxine as she had under-secreted it. Describe the symptoms of over-secretion of thyroxine. Identify the disorder associated with the over-secretion of thyroxine and outline a possible treatment.

10. Is hyperthyroidism different from Grave’s Disease? Explain.

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Antagonistic Hormones Regulate Calcium Levels

Two antagonistic hormones, which are hormones that work in opposition to one another to establish overall balance or homeostasis, regulate calcium levels in the blood. One of these hormones, calcitonin, originates from the thyroid gland, and the other, parathyroid hormone, from the parathyroid glands. To gain an understanding of where these hormones are secreted, how they function to maintain calcium homeostasis, how their secretion is regulated, and what happens when calcium balance is disrupted, research and answer the following questions in Try This #3. As in Try This #2, the completed answers to these questions can become your notes for this part of Lesson 4. Where appropriate, answer in complete sentences. You may use library sources, the Internet, page 449 in your textbook, or any other resources to which you have access that will help you complete the questions. When you have finished the questions, check your answers and file your work in your course folder. Seek help from your instructor to explain any difficulty that you may have encountered.

Try This

TR 3.

1. Describe at least three functions of calcium in the body.
2. Calcium homeostasis is mainly regulated by two hormones. Identify the two hormones and the glands that produce each of them.
3. The two hormones that you identified in Question #2 are described as being antagonistic hormones. Define what is meant by this.
4. Describe the mechanism of calcitonin function.
5. Outline the regulation of blood calcium levels by calcitonin.

Use the following additional information to answer the next four questions.

FMEN 1 patients often develop minute tumors in the parathyroid glands. This happened to Emily. Consequently her parathyroid glands over-secrete parathyroid hormone.

6. Describe the overall effect of parathyroid hormone. Outline three specific actions on the body caused by this hormone to achieve its overall effect.
7. 
   © Troy Kellogg/shutterstock
   Emily had fallen on a very icy sidewalk and had broken some bones in her wrist. The bones were reset, but months later they still had not healed. During this time Emily landed in the emergency room of the hospital with severe abdominal pain which was diagnosed as a case of kidney stones. Construct a hypothesis that may explain the underlying cause of both health problems. (Remember, a hypothesis should be in the form of an “If … Then … Because …” statement.)

8. Draw a negative feedback loop that illustrates the regulation of blood calcium levels by parathyroid hormone.

9. How would Emily’s feedback loop be different?

Self-Check

Do the following Self Check, which consists of some multiple choice questions and a couple of numerical response questions, in preparation for completing the lesson assessment. Check your answers and, if you do not understand any of the concepts, be sure to discuss these with your instructor. The Diploma exam will be composed of questions that are similar in style to the following questions. It is a good idea to practice these types of questions as much as possible.

Use the following diagram to answer the next two questions.

1. Which endocrine gland shown in this illustration would be directly responsible for the development of bone thinning if it was overproducing its hormones?
   
   
   1. 2
   2. 3
   3. 4
   4. 6
2. Cretinism can develop if low secretions of hormone are produced by the gland labeled
   
   
   1. 2
   2. 3
   3. 4
   4. Both 2 and 4
3. Hypothyroidism that developed in childhood would be characterized by
   
   
   1. impaired physical and mental development
   2. thirst and consumption of large volumes of water
   3. increased blood pressure and increased heart rate
   4. suppression of the immune system and the development of goiter
4. The area of the brain that normally initiates the secretion of TSH is the
   
   
   1. medulla oblongata
   2. cerebrum
   3. pons
   4. hypothalamus
5. A condition that results in an enlargement of the thyroid gland may be caused by a diet deficient in
   
   
   1. salt
   2. iron
   3. iodine
   4. sodium

Use the following information to answer the next three questions.

Vegetables such as cabbage, rutabaga, and turnips contain goitrin, a substance that inhibits iodine uptake by the body.

6. A person with a diet high in vegetables containing goitrin may gain weight fairly rapidly. A possible explanation for this weight gain would be
   
   
   1. increased protein metabolism
   2. decreased blood sugar levels
   3. increased glycogen release
   4. decreased metabolic rate
7. The function of which gland would be most affected by goitrin?
   
   
   1. anterior pituitary
   2. adrenal cortex
   3. thyroid gland
   4. parathyroid gland
8. An increase in goitrin consumption would likely cause a person to experience increased
   
   
   1. fatigue
   2. heart rate
   3. breathing rate
   4. blood pressure

Use the following information to answer the next two questions.

On April 26, 1986, a major accident occurred at a nuclear generating station in Chernobyl. The nuclear explosion dispersed several tons of radioactive iodine, cesium, uranium, and other elements five kilometers into the air.

Radioactivity is extremely damaging to living cells.

From Biosphere 2000: Protecting Our Global Environment

9. As soon as people in Europe realized there had been a nuclear accident, they rushed to buy iodine tablets. What reason would people have for consuming large quantities of iodine?
   
   
   1. So that iodine from the tablets, instead of the radioactive iodine, would accumulate in the thyroid
   2. Because iodine, by negative feedback, blocks the formation of TSH, therefore protecting the thyroid from radioactivity
   3. Because iodine inhibits cell division, thereby reducing the amount of cellular damage occurring during exposure to radiation
   4. So that iodine from the tablets could accumulate in the hypothalamus and block radioactivity from killing/altering body cells
10. In addition to symptoms of radiation poisoning, which symptoms would be expected among people who did not take iodine tablets?
    
    
    1. Pancreatic dysfunction and insufficient insulin production
    2. Metabolic dysfunction resulting in fatigue and weight gain
    3. Increased ACTH secretion and puffiness of face, chest, and abdomen
    4. Pituitary dysfunction resulting in increased hGH secretion and development of gigantism

Use the following information to answer the next question.

Some Glands and Hormones of the Human Body

Numerical Response

11. Select a set of numbers for glands and hormones that correctly completes the statement below.
    
    The ______ secretes ______ which stimulates the ______ to produce ______,
          (gland)             (hormone)                          (gland)                (hormone)
    
    which regulates metabolism (cellular respiration).

Numerical Response

Use the following information to answer the next question.

Endocrine Glands

1. adrenal medulla
2. anterior pituitary
3. posterior pituitary
4. thyroid
5. parathyroid gland
6. adrenal cortex

12. Using the numbers that represent the endocrine glands shown above, match the hormone below to the endocrine gland that produces it.

Endocrine Gland:          ________                  ______           ______           _______
Hormone:                   Thyroxine                    PTH                TSH                Calcitonin

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Lesson Summary

This lesson explored the following focusing question:

• How do the thyroid and parathyroid glands contribute to homeostasis

The thyroid gland, a butterfly shaped gland located just below the larynx, has embedded in it the four pea sized parathyroid glands. These glands produce two antagonistic hormones—calcitonin and PTH—that work together to maintain blood calcium homeostasis. Through mechanisms such as increasing absorption of calcium from food or urine and by stimulating decomposition of bone tissue, PTH increases blood calcium levels. Calcitonin decreases blood calcium levels by stimulating uptake of calcium by the bones and inhibiting decomposition of bone tissue. Both are regulated by negative feedback mechanisms.

When stimulated by TSH from the anterior pituitary, the thyroid gland also produces thyroxine which increases metabolism (cellular respiration) in every cell of your body and especially in cardiac cells, muscle cells, and cells of the kidney and liver. It stimulates the liver to convert glycogen to glucose and increases body temperature. Thyroxine also stimulates proper development and function of the nervous system. Iodine is required to synthesize thyroxine. Lack of thyroxine is called hypothyroidism and presents differently in babies/children and adults. Overproduction is called hyperthyroidism. Goitre, myxedema and cretinism are disorders caused by imbalances in thyroxine. Thyroxine levels are regulated by negative feedback of the tropic hormone TSH produced by the anterior pituitary. Surgical removal of parts of the thyroid, death of the most active follicle cells initiated by radioactive iodine and consumption of thyroid pills are medical technologies that can treat thyroxine imbalances.

Glossary

metabolism: all of the chemical reactions which occur in living organisms that support and sustain its life processes; one type involves the build-up or synthesis of complex compounds from simple ones, and a second type consists of the breakdown or decomposition of complex compounds into simple ones; cellular respiration is one of the major metabolic processes

cellular respiration: a process occurring in the mitochondria of cells of all living organisms in which energy rich compounds such as carbohydrates (glucose), proteins, and fats are burned with oxygen to release energy in form of ATP, and waste products such as water and carbon dioxide

follicle: as it relates to the thyroid gland, is a microscopic structure consisting of a circle of cells called follicle cells surrounding a central cavity; thyroid gland consists of many follicles

central cavity: also called the lumen, is surrounded by follicle cells and stores the precursor for thyroxine formation
follicle cells: as they relate to the thyroid gland, they are the cells that surround the central cavity and are responsible for storing iodine and synthesizing thyroxine from the precursor

C cells: also called parafollicular cells, they are located between the follicles of the thyroid gland and are responsible for synthesizing calcitonin

calcitonin: hormone produced by the C cells (parafollicular cells) in the thyroid gland that decreases blood calcium levels by increasing uptake of calcium into the skeleton and inhibiting decomposition of bone when the blood levels of calcium are too high

thyroxine: hormone produced by the follicle cells of the thyroid gland; mainly controls the rate at which the body metabolizes carbohydrates, fats, and proteins for energy and stimulates the proper development of the nervous system

precursor: an inactive form of a molecule that can easily be changed into the active form; the precursor thyroglobin can easily be changed into the active thyroxine by the addition of iodine atoms

goitre: sometimes called endemic goitre, is an enlargement of the thyroid gland caused by a lack of iodine, which is necessary for the production of thyroxine

exothalmic goitre: an enlargement of the thyroid gland caused by the overactivity of the thyroid gland due to over-stimulation

hypothyroidism: disorder of the thyroid gland indicated by a lack of thyroxine, which may be caused by a ack of dietary iodine or a lack of TSH

hyperthyroidism: overactivity of the thyroid gland that leads to high levels of thyroxine and subsequent speeding up of bodily functions

myxedema: form of hypothyroidism in adults

cretinism: form of hypothyroidism in infants and young children

Grave’s Disease: an autoimmune disorder caused by an abnormal protein which stimulates the thyroid gland to produce and secrete excess thyroxine; most common cause of hyperthyroidism 

Lessonn 1.2.5

Lesson 5—The Pancreas

Get Focused

left: © Marc Dietrich/shutterstock, rig© Hannamariah / Barbara Helgason/shutterstock

It is just before lunch, you are feeling hungry, tired, light-headed, and you are worried about a big exam in the afternoon. This is stress! What do you grab to eat? Are you the quick candy bar type, or are you the protein-based tuna sandwich type? Which one do you think would get rid of those symptoms you are experiencing, and get you through the exam without you having a complete collapse and meltdown? This situation is all about the pancreas and how it manages that blood sugar high, or low. For a diabetic this is a daily balancing act, and one that can have very serious consequences if not managed properly. Next time you are feeling exhausted, think about Emily and how her pancreas cannot regulate her blood sugar level. The tiny tumors growing in the islet cells of her pancreas cause havoc with the levels of her pancreatic hormones. That tuna sandwich will not make a difference for her, but the candy bar may save her life.

To understand the role of the pancreas in the endocrine system, you will investigate the following focusing question:

• How does the pancreas contribute to homeostasis?

This lesson should take approximately 2.0 – 2.5 hours to complete.

Module 2: Lesson 5 Assignments

While you are completing this lesson, there will be many opportunities for you to learn, understand and practice the concepts that are presented. After completing these assignments as well as your summary notes, file everything in your course folder for reference when you are preparing for exams.

Remember, you have the option of trying additional questions from the textbook for further practice. Consult with your instructor for answers to these questions. “The Key” will provide you with many Diploma exam style multiple choice, numerical response, and written response questions that will be an excellent review of the module, as well as good preparation for the Diploma exam.

 Once you have completed all of the learning activities for this lesson, you can complete the online assignment.

Bio30 1.2.5 online assignment

You should also watch the tutorial video for this lesson. Bio30 tut#1.2.5 Blood sugar regulation

You must decide what to do with the questions that are not marked by the teacher.

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all of the questions and place those answers in your course folder.

1.2.5 page 2

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The Anatomy of the Pancreas

Located in the space between the stomach and the first loop of the small intestine, the pancreas is a dual function organ. In Biology 20, you learned about the digestive enzymes that it produces. Scattered among the enzyme-producing cells are clusters of cells called the islets of Langerhans (or simply islets) which produce pancreatic hormones. The vast majority of cells in the islets are beta cells, which produce insulin. A few elongated alpha cells produce glucagon. Look at the photomicrograph above and see if you can distinguish the two types of cells in the islet.

Read

Watch and Listen

Study Figure 13.24 on page 456 of your textbook to help you do this. HOWEVER, IN THIS FIGURE THE LABELS FOR THE ALPHA AND BETA CELLS SHOULD BE REVERSED. THE BETA CELLS ARE MORE NUMEROUS.

To give you a better understanding of the structures of the pancreas, read page 456 in your textbook OR view the video below.

The Pancreas

Try This

TR 1.

To apply your knowledge of the anatomy of the pancreas and the function of its various structures, label the structures on the Pancreatic Tissue and Associated Structures Handout and on the diagram, annotate the structures with their functions. Several structures are shown that you have studied in previous lessons. After you have completed the exercise, check your answers and file your work in your course folder.

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), BLM 13.4.1. Reproduced by permission.

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Pancreatic Hormones

Like calcitonin and PTH, produced by the thyroid and parathyroid glands, insulin and glucagon produced by the pancreas are antagonistic hormones, responsible for regulating blood glucose. Insulin, through its mechanisms, lowers blood glucose levels while glucagon, through its mechanisms, raises levels of blood glucose. Together, these hormones maintain homeostasis by way of negative feedback. Restoration to a range of normal glucose levels acts to control hormone secretion.

Read and make notes from pp. 456 – 457 of your textbook, which describes how pancreatic hormones maintain blood glucose levels. A good summary of negative feedback is given in Figure 13.25 on p. 457 of the textbook. File your notes, including the feedback loop diagram, in your course folder.

Try This

TR 2.

Now that you know about blood glucose regulation by insulin and glucagon, complete the following closed written response question which has four parts. Notice that mark values have been assigned for each part. The key to this exercise will explain how the mark values are assigned, and when you check your answers, mark each part accordingly. After checking this exercise, file it in your course folder. Consult your instructor if you require clarification or help.

Use the following information to answer the following question.

Blood glucose concentrations of one individual were monitored over several hours. The following data was collected. The blood glucose level of a healthy person is approximately 90 mg/100 mL.

1. Plot this data on the grid provided below. Draw a curved line through the points and label your graph appropriately. Draw a horizontal dotted line showing the approximate blood glucose level of a healthy individual. (6 marks)
   
   

2. On the graph, indicate with an arrow, two places where a blood test would reveal high levels of insulin. Explain why insulin would be at high levels at these times. (4 marks)
3. Predict what would happen to this person’s blood glucose levels if he/she worked out at the gym from 9:00 am to 10:00 am. With respect to blood glucose levels, how would his/her body respond?
4. The graph shows that this person’s glucose levels fluctuate throughout the day. Is this person healthy or does he/she have a malfunctioning pancreas? Explain your answer. (3 marks)

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Blood Glucose Imbalances

Among your friends, relatives, and teachers, you are likely to know someone who has diabetes mellitus. This is a disorder in which blood glucose levels are abnormally high because the pancreas does not produce enough insulin, or the body cells do not respond to the insulin that the body produces. Doctors usually use the full name rather than diabetes alone to distinguish it from diabetes insipidus, which has nothing to do with blood glucose levels. Do you remember what happens in this disorder ? Lack of insulin causes blood glucose levels to spike after meals and to remain high for long periods of time. This is called hyperglycemia. If there is too much insulin, glucose levels plummet and the person has hypoglycemia (a hypoglycemic episode). Diabetes is usually grouped as Type 1 diabetes (also called insulin dependent/juvenile diabetes) or Type 2 diabetes (also called insulin independent/adult onset diabetes). Untreated glucose imbalances lead to many symptoms and can result in blindness, kidney failure, nerve damage and severe infection in the limbs, which may lead to the need for amputation. Several medical technologies have been developed to help diabetics deal with their problems.

© PeJo/shutterstock

left: © Adam Majchrzak/shutterstock, rig© ajt/shutterstock

Read

Read pp. 457 – 459 of your textbook and make notes on the types of diabetes, the causes, the symptoms, the effects, and the medical technologies that have been developed to deal with glucose imbalances. File your work in your course folder.

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Watch and Listen

You can view the following video, make notes on the same concepts and file your notes in your course folder.

Type 1 Diabetes

Diabetes Mellitus

Urinalysis

Blood Glucose Monitoring

Research Approaches for Diabetes

Try This

TR 3. 

Apply what you have learned about diabetes mellitus by completing the questions in this exercise. Check your answers and file your work. Consult your instructor for clarification of any concepts.

1. Complete the following chart that illustrates normal blood glucose regulation through negative feedback.
   
   
2. Complete the following table by comparing Type 1 diabetes with Type 2 diabetes.
   
   

   A Comparison of Type 1 Diabetes with Type 2 Diabetes

   
   

   Feature	Type 1 Diabetes	Type 2 Diabetes
   Cause
   Onset
   Age of Onset
   Predisposition
   Insulin Production
   Immediate Symptoms
   Long Term Effects
   Treatment

3. FMEN 1 wreaks havoc with the levels of Emily’s pancreatic hormones. Rather than being hyperglycemic, she is hypoglycemic. Tiny islet cell tumors affect the beta cells and cause an over-secretion of insulin.
   
   
   1. Differentiate between hyperglycemia and hypoglycemia.
   2. Describe what happens to the blood glucose level when there is an over-secretion of insulin.
   3. Outline how a person, such as Emily, reacts to hypoglycemia.
   4. Explain what other hormone may also be over-secreted as the pancreas tries to deal with the low blood glucose levels.
   5. What can Emily do to alleviate the symptoms quickly?

Use the following graph to answer the next question.

4. 
   
   1. What occurred at Point X?
   2. Identify the endocrine secretion represented by A.
   3. What happened at Point Y?
   4. Identify the endocrine secretion represented by B.

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Self Check

Apply your understanding of the concepts on the pancreas and its regulation of blood glucose by answering the multiple choice and numerical response questions that follow. Check your answers. If you do not understand any questions, consult with your instructor.

1. Which of the following rows correctly matches the endocrine gland to the hormone it secreted and to the effect caused by the hormone?
   
   

   Row	Endocrine Gland	Hormone Secreted	Target Cell/Organ
   a.	Thyroid Gland	Thyroxine	Increases blood glucose
   b.	Pancreas	Insulin	Increases blood glucose
   c.	Pancreas	Glucagon	Increases blood glucose
   d.	Adrenal cortex	Epinephrine	Increases blood glucose

2. Which hormone is not correctly matched to the disorder/disease associated with it?
   
   
   1. insulin and diabetes mellitus
   2. aldosterone and diabetes insipidus
   3. thyroxine and goitre
   4. cortisol and depressed immune system
3. Which of the following hormones does not affect the carbohydrate metabolism?
   
   
   1. human growth hormone
   2. epinephrine
   3. insulin
   4. ADH
4. Which of the following endocrine glands does not produce a hormone that directly affects blood glucose levels?
   
   
   1. posterior pituitary
   2. pancreas
   3. adrenal glands
   4. thyroid gland
5. Which of the following explains one of the differences between Type 1 and Type 2 diabetes?
   
   
   1. The treatment for Type 2 diabetes involves insulin injections, while Type 1 can usually be controlled by diet.
   2. Only Type 1 can result in complications such as kidney disease, reduced circulation, or stroke.
   3. Type 1 can be a result of lifestyle, and Type 2 is thought to be caused by a virus or other agent.
   4. People with Type 2 diabetes can produce insulin, but this insulin cannot be used; Type 1 diabetes results from lack of insulin production.
6. Which pair consists of antagonistic hormones?
   
   
   1. thyroxine and calcitonin
   2. epinephrine and norepinephrine
   3. cortisol and epinephrine
   4. insulin and glucagon

Use the following diagram to answer the next three questions.

7. Which of the following rows correctly matches the endocrine gland labeled in the diagram to the hormone it produces?

8. Which endocrine gland shown on this diagram would be directly responsible for the development of diabetes mellitus in humans?
   
   
   1. B
   2. D
   3. E
   4. F
9. Symptoms resulting from low secretions of the hormones produced by the gland labeled F include
   
   
   1. high levels of sodium and sugar in the urine
   2. increased thirst and decreased urine production
   3. loss of weight and high levels of glucose in the urine
   4. obesity and increased risk of stroke
10. The endocrine function of the pancreas was studied in Canada using dogs as experimental animals. The pancreatic cells with an endocrine function are
    1. islet cells
    2. C cells
    3. follicle cells
    4. interstitial cells

Use the following diagram to answer the next question.

11. Hormones X and Y, respectively, are
    
    
    1. insulin and glucagon
    2. glucagon and insulin
    3. insulin and epinephrine
    4. epinephrine and insulin

Use the following information to answer the next two questions.

 

A Treatment for Pancreatitis

Surgical removal of the pancreas is a procedure that doctors use to relieve the pain of patients suffering from chronic pancreatitis (inflammation of the pancreas). Unfortunately, the surgery causes the onset of diabetes mellitus and other complications in these patients. In a recent study involving five individuals who had undergone this treatment, islet cells from the removed pancreas were infused (transplanted) back into the liver of each patient. This procedure effectively eliminated the occurrence of diabetes in these patients.

 

12. Blood glucose levels are kept relatively constant by a negative feedback mechanism. The islet cells are part of this mechanism. The role of these cells is to secrete
    
    
    1. glucagon to raise blood glucose levels, and insulin to lower blood glucose levels
    2. glucagon to lower blood glucose levels, and insulin to raise blood glucose levels
    3. glucagon and insulin, both of which lower blood glucose leve
    4. glucagon and insulin, both of which raise blood glucose levels
13. Patients who participated in this study no longer have a pancreas. To maintain normal body functions in these patients, the infusion of islet cells would have to be accompanied by a daily intake of
    
    
    1. glycogen to stimulate liver function
    2. hormones to promote glycogen release from the liver
    3. digestive enzymes into the blood to maintain nutrient levels
    4. digestive enzymes to replace those produced by the pancreas

Use the following information to answer the next question.

 

Responses Stimulated by Hormones

 

1. Release of thyroxine
2. Growth of bones
3. Water reabsorption by kidneys
4. Conversion of protein and fat to glucose
5. Conversion of glucose to glycogen
6. Conversion of glycogen to glucose

 

Numerical Response

14. Identify the response, as numbered above that would be stimulated by each of the hormones given below.
    
    Response:
                            ______           ______           ______                       ______
    Hormone:     Insulin           Cortisol         Glucagon                  hGH

 

Numerical Response

Use the following information to answer the next question.

 

Some Endocrine Glands and Hormones

1. Adrenal Cortex
2. Insulin
3. Epinephrine
4. Pancreas
5. Glucagon
6. Human Growth Hormone
7. Anterior Pituitar

15. To complete this statement, select the number of the gland or hormone from the information above that best completes each blank.
    
    

    The hormones of the _____ act antagonistically to regulate blood glucose levels.  The beta cells of the islets of Langerhans secrete ____, which lowers blood glucose levels. The alpha cells secrete _____, which raises blood glucose levels.  Type 1 diabetes causes hyperglycemia because the secreting cells have degenerated. Type 2 diabetes tends to develop gradually, often because the _____ receptors on the body’s cells stop responding to this hormone.

 

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Reflect and Connect

Suppose you have a 92 year old grandfather who lives in an extended care facility. He is sharp as a tack, but has Type 2 diabetes mellitus. He is very conscientious about making sure that he injects his insulin regularly. You go to visit him and he tells you about an incident that really scared him. He relates how he had become ill and experienced vomiting and diarrhea all day. He thinks that this was caused by the institutional food! He lost his appetite for eating but injected his insulin normally. A nurse found him unconscious on the floor of his room. Luckily the facility physician diagnosed the cause and helped him. He asks you to help him understand what happened. What would you say? Think about what you have learned in this lesson. Can you suggest what condition may have occurred in your grandfather’s blood because he stopped eating, but continued to inject insulin? Can you predict what the physician did to treat your grandfather? Did your grandfather forget to monitor his blood glucose? Should he have been injecting the insulin if he was not eating? Did he know this? Can you review with your grandfather what the role of insulin that he injects has in his body? You may want to discuss these questions with your instructor to verify your ideas. Then, proceed with the following assessment and submit it to your instructor.

Module 2: Lesson 5 Assignment

You can now complete your online assignment 1.2.5

As you review this lesson, apply your knowledge to develop hypotheses about:

• the effect the tumors in the islets of the pancreas had on Emily
• the effect to Emily’s blood glucose levels 
• about whether or not Emily became a diabetic
• Technologies and treatments that would be available, and how they would help Emily establish homeostasis.

Going Beyond

A University of Alberta research team has developed a procedure called the Edmonton Protocol that helps people who difficulty managing Type 1 diabetes undergo an islet transplant procedure. Read page 466 in your textbook which is an interview with Dr. Edmond Ryan, Medical Director of the University of Alberta Clinical Islet Transplant Program.

1. Research how islet transplantation in the Edmonton Protocol is performed.
2. Islet transplant patients must wait for the treatment until donated organs become available. Outline three other potential sources of islet cells and outline the issues related with each source.
3. Explain why stem cell research is important to islet cell transplantation

Lesson Summary

Communication of information to and from a command centre in a battle is essential for success. The pancreas is like a command centre which monitors blood glucose. High levels of glucose stimulate the beta cells in the islets of the pancreas to secrete insulin, which increases the passage of glucose into body cells and promotes the conversion of glucose to glycogen in liver and muscle cells, and to fat in the adipose cells. Low glucose levels stimulate the pancreatic alpha cells in the islets to secrete glucagon which promotes the breakdown of glycogen to glucose, and the release of this glucose into the bloodstream.

When the communication is disrupted, the battle may be lost. So it is with blood glucose regulation. If the beta cells are destroyed by an autoimmune disease and little or no insulin is produced, consistently high blood glucose levels result in Type 1 diabetes. Left untreated, life-threatening consequences result.

Regular glucose monitoring and insulin injections are the only treatment. Insulin cannot be taken in pill form because the digestive system would break it down before it could be absorbed. As a command centre, if the pancreas sends out insulin but the body cells ignore it (called insulin resistance), Type 2 diabetes results. Being very fat (obese) increases the cells inability to respond to insulin. The obvious treatment is to lose weight. Controlling diet and regular exercise can persuade the cells to respond to the insulin. In some cases drugs have to be used.

Sometimes the pancreas secretes too much insulin and hypoglycemia occurs. The person becomes anxious, nervous, develops shakiness and has a feeling of weakness. Continued hypoglycemia causes the brain to become disoriented and may progress to unconsciousness and possibly death. If symptoms are recognized quickly, it is easily treated by eating candy or injecting glucagon.

Medical technologies for dealing with diabetes mellitus have progressed from glucose dipsticks to digital glucose monitors, and from syringes to insulin pens to insulin pumps. Hard to manage cases can be treated with islet transplants.

Glossary

alpha cells: cells in the islets that secrete glucagon

beta cells: cells in the islets that secrete insulin

diabetes mellitus: a serious chronic disorder that results when the pancreas does not produce enough insulin, insulin receptors, or body cells do not respond to insulin; levels of blood glucose tend to rise sharply (spike) after meals (hyperglycemia) and remain at significantly elevated levels

glucagon: a hormone, secreted by the alpha cells in the islets of the pancreas, which raises blood glucose levels by stimulating liver cells to convert glycogen to glucose; also stimulates fat cells (adipose cells) to convert fat to glucose

hyperglycemia: a condition resulting from high levels of blood glucose; occurs in individuals with diabetes mellitus

hypoglycemia: a condition resulting from low levels of blood glucose; occurs in individuals who secrete excessive amounts of insulin when a tumor develops in the beta cells, or in diabetics who have injected too much insulin

insulin: a hormone, secreted by the beta cells in the islets of the pancreas, which lowers blood glucose levels by promoting the uptake of glucose by most cells of the body, and the synthesis and storage of glycogen in the liver; also stimulates protein and fat synthesis

islets: also called the islets of Langerhans; composed of clusters of alpha and beta cells which secrete glucagon and insulin, respectively, into the blood

pancreas: a gland with dual function; the non-endocrine part secretes digestive enzymes into the intestine through the pancreatic duct, while the endocrine portion called the islets of Langerhans secretes insulin and glucagon into the bloodstream
Type 1 diabetes: also called juvenile diabetes or insulin-dependent diabetes; an autoimmune disorder in which the immune system produces antibodies that attack and destroy the beta cells of the pancreas so that they are unable to produce insulin; usually diagnosed at an early age and the individuals require daily injections of insulin

Type 2 diabetes: also called adult-onset diabetes or insulin-independent diabetes; a disorder that develops slowly over time because the insulin receptors on the body’s cells stop responding to insulin, or because the beta cells of the pancreas produce less and less insulin over time; appears to be related to overweight and obese individuals

Lesson 1.2.6

Lesson 6—Bringing it Together

Get Focused

In the previous module you learned how the nervous system responds to environmental stimuli by using neural pathways to produce very rapid and precise responses. The endocrine system responds to stimuli by using chemical messengers in the blood to control metabolic processes in the body. This process is much slower than control by the nervous system, with the exception of the responses controlled by epinephrine. Your body is in balance (homeostasis) because your nervous system responds to immediate stimuli or crises while your hormonal system maintains long term stability. A major part of this balance is missing from Emily’s life. She doesn’t have the opportunity to make any decisions regarding the balance of her endocrine system, or how that system will impact her health and life. The decisions you make and the overall health of your nervous and endocrine systems can impact your life now and in the long run.

This lesson will allow you to explore how the nervous and endocrine systems complement and communicate with each other to maintain homeostasis and your well being by investigating the following focusing question:

• How are the nervous and endocrine systems interdependent and how are they different?

This lesson should take approximately 1.0 – 1.5 hours to complete.

Module 2: Lesson 6 Assignment

While you are completing this lesson, there will be many opportunities for you to learn, understand and practice the concepts that are presented. After completing these assignments as well as your summary notes, file everything in your course folder for reference when you are preparing for exams.

Remember, you have the option of trying additional questions from the textbook for further practice. Consult with your instructor for answers for these questions. “The Key” will provide you with many diploma-style multiple choice, numerical response, and written answer questions that will be an excellent review of the module and good preparation for the diploma exam.

Once you have completed all of the learning activities for this lesson, you can complete the online assignment.

Bio 30 1.2.6 online assignment

You should also watch the tutorial video for this lesson and submit a summary.  Bio30 tut#1.2.6 Enzyme Actions

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all of the questions and place those answers in your course folder.

1.2.6 page 2

Explore

Read

Regulating the Internal Environment

You and your friends are at a rock concert. Coloured lights are flashing, and the music is loud. You are dancing with your friends and having a great time. You see the changing lights; you hear and feel the music; you sense the temperature of the room. Heart rate, breathing rate, body temperature, and sweating are all increased. Your body is able to detect and respond to environmental change and your internal environment is regulated by the two control systems you have studied in this unit: the nervous and endocrine systems. Structurally different in many ways, the two systems must constantly interact to control physiological processes such as heart rate.

Read page 436 in your textbook to explore how the nervous and endocrine systems are different.

Try This

TR 1.

As part of your notes from your reading, construct a table that contrasts the two systems in respect to the following features: method of communication, speed of communication, duration of response, target pathway and what action is brought about by the effectors. Check your table and file it in your course folder.

Self-Check Answers

TR 1.

Your table for contrasting (identifying differences) between the nervous and endocrine systems should resemble the one below.

Contrasting the Nervous and Endocrine Systems

1.2.6 page 3

Read

Watch and Listen

The Brain and the Pituitary Gland

The hypothalamus—an important part of the brain—is located just above the pituitary gland—an important part of the endocrine system. Information is transmitted to the hypothalamus through sensory pathways from the sense organs. Based on this information, the hypothalamus controls and integrates many basic physiological activities including the reflex activity of the autonomic nervous system, of which the sympathetic nervous system is a part. In the hypothalamus there are two groups of nerve centres. One is connected to the anterior lobe of the pituitary by blood vessels, and the other is connected to the posterior lobe by nerve cells. These centres send instructions to the two parts of the pituitary, telling them whether or not to release their hormones into the bloodstream. However, the nerve centres communicate with the two parts of the pituitary gland in different ways. Releasing hormones are secreted by one nerve centre and carried to the anterior pituitary through the blood vessels, where they regulate the secretions of the anterior pituitary. Can you recall an example of this that you have studied? A second nerve centre, connected to the posterior lobe by nerve cells, performs two functions: (1) it secretes hormones which are carried by the nerve cells to the posterior pituitary where they are stored in the axon terminals and (2) it sends nerve impulses to the posterior pituitary, stimulating the release of the stored hormones. Can you identify the two hormones that are stored in the posterior pituitary? A third centre in the hypothalamus is connected by sympathetic neurons to the adrenal gland. Can you remember which hormone is released by the adrenal gland when these neurons are stimulated? These examples illustrate the importance of the hypothalamus as an important command centre for coordinating the activity of the nervous and endocrine systems.

For further discussion:

Read page 437 and page 463 of your textbook and make notes on how the nervous and endocrine systems maintain homeostasis, how they are coordinated, and how they act together. Developing a flow chart may help you visualize these relationships. You may want to review your notes, particularly from Module 2 Lessons 1, 2, 3 and 4. File your summarized notes in your course folder for later reference.

OR

You can investigate the same concepts by watching and making notes on the following videos. File your notes in your course folder.

Nervous vs Endocrine Action

Try This

TR 2.

To help you apply your understanding of the concepts in this lesson, complete the following questions by answering in complete sentences. Check your answers and then file your work in your course folder. Consult with your instructor for clarification.

1. Using an example, explain how the nervous and endocrine systems work together to regulate a response in the body.
2. 1. Why has the pituitary gland often been called the “master gland”?
   2. Explain how the hypothalamus controls the pituitary gland.
   3. Is “master gland” a suitable name for the pituitary gland?
3. Explain how the anterior and posterior pituitary differ with respect to their relationships to the hypothalamus.
4. How are neurotransmitters and hormones similar and how are they different?
5. Using an example, explain how the hormones of the adrenal medulla complement the actions of the sympathetic branch of the autonomic nervous system.
6. Compare and contrast the role of the norepinephrine in the nervous system with its role in the endocrine system.
7. How is the hypothalamus involved in the release of epinephrine and norepinephrine by the adrenal gland?
8. How is the secretion of tropic hormones from the pituitary gland regulated?
9. Compare the anatomy of the pituitary gland and adrenal medulla.
10. Why is control of the adrenal medulla by the nervous system important?

1.2.6 page 4

Self-Check

After a review of the lesson, complete the following multiple choice questions. Check your answers. Discuss with your instructor any concepts that you do not understand.

1. All of the following statements about hormones are correct except
   
   
   1. They are produced by endocrine glands
   2. They travel to target cells in the body
   3. They are carried by the circulatory system
   4. They are used to communicate between different organisms
      
      
2. The hypothalamus controls the anterior pituitary by means of
   
   
   1. tropic hormones carried by nerve cells
   2. nervous stimulation by the sympathetic nervous system
   3. releasing hormones in the bloodstream
   4. both nervous and hormonal stimulation
      
      
3. All of the following statements about the hypothalamus are correct except
   
   
   1. It functions as an endocrine gland
   2. It is part of the central nervous system
   3. It is subject to negative feedback.
   4. Its neurosecretory cells terminate in the anterior pituitary
      
      
4. Which of the following glands is controlled directly by the hypothalamus or central nervous system and not the anterior pituitary?
   
   
   1. pancreas
   2. adrenal medulla
   3. adrenal cortex
   4. posterior pituitary
      
      
5. In humans, the nervous and endocrine systems are similar in that both
   
   
   1. secrete chemical messages
   2. operate at the voluntary and involuntary level
   3. use highly specialized pathways
   4. respond very rapidly to stimuli
      
      
6. The main difference between the endocrine and nervous system is that only the endocrine system
   
   
   1. secretes chemical messengers
   2. is regulated by negative feedback
   3. depends on specialized neurosecretory cells
   4. relies completely on the circulatory system for transport
      
      
7. Compared with the response to a nerve impulse, the response to a hormone is usually
   
   
   1. shorter in duration and more widespread in effect
   2. shorter in duration and less widespread in effect
   3. longer in duration and more widespread in effect
   4. longer in duration and less widespread in effect

Lesson Summary

Inside your body, an action-packed medical emergency room drama is played out every minute of your life. If you were to photograph your blood and the nearby cells, you would see an incredible amount of ordered activity. For example, if you were to view thyroxine molecules being carried by the bloodstream and then persistently attaching themselves to muscle cells, you would see glycogen molecules being stimulated to change to glucose, mitochondria going into high gear and belting out ATP, and the blood warming up. This is the action of the endocrine system. However, it does not act alone it interacts with the nervous system to coordinate and integrate its activities. The release of those thyroxine molecules was stimulated by the release of thyroid stimulating hormone from the anterior pituitary, which was in turn regulated by the releasing hormones from the hypothalamus, an important coordinating centre in the brain. High levels of thyroxine shut down the releasing hormones and TSH by negative feedback.

The nervous system operates like our telephone system, whereas the endocrine system works more like our postal system. The nervous system regulates the activity of muscles and glands through electrochemical impulses in specific neural pathways that travel to them in milliseconds. The endocrine system influences cells by means of hormones carried by the blood. There is a lag period of seconds, minutes, sometimes days, or even years before the target tissue responds. Hormones target a broader range of cells than nerves do and they have widespread and diverse effects. The major processes controlled by hormones include reproduction (Unit B), growth and development (of the body and nervous system), reaction of the body to stress, maintenance of ion concentrations (sodium, calcium), water and nutrient (glucose) levels, and regulation of metabolism and energy balance.

Both systems include responses regulated by negative feedback. Epinephrine and norepinephrine are common to both systems. Nervous tissue, such as that in the posterior pituitary, the adrenal gland, and the hypothalamus secretes hormones. Some hormones influence the normal development and function of the nervous system (thyroxine and human growth hormone). Some processes cannot be regulated without both systems working together: homeostasis depends upon both systems. When this balance is disrupted, medical technologies developed by scientists, such as synthetic insulin, thyroxine, and ADH pills, glucose monitors, insulin pens, various surgeries and radiation treatments are used to re-establish it.

Unit 1 Conclusion and Assessment

In the first unit of Biology 30, you examined the structure and function of the nervous and endocrine systems in detail. Specifically, you worked on

• describing how the nervous and endocrine systems maintain homeostasis
• explaining how the human body maintains equilibrium between its internal and external environments
• describing what physiological processes and control systems are involved in maintaining homeostasis
• analyzing what medical technologies are available to treat disorders of the nervous and endocrine systems

You saw how humans interact with their internal and external environments, and how the nervous and endocrine systems respond to maintain equilibrium and system health. Your exploration showed you the role of technology in detecting, analyzing, and enhancing the functions of these systems.

There were two modules in this unit. The first module looked at the nervous system, which responds to internal and external stimulation. Here you explored how the nervous system communicates this information throughout the body. The second module focused on the role of the endocrine system and how it works to support homeostasis by releasing hormones into the blood.