Module 2 The Endocrine System

Lesson 1.2.3

1.2.3 page 5

Read

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.

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

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

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.

What is the difference in the way that aldosterone and ADH affect water balance?
Why are sodium ions important in the body?
How does aldosterone help the body cope with an ongoing stressful situation? How is this response different from the “fight or flight” response?

Check your work.

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.

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

Features

Cushing’s Disease

Addison’s Disease

Hormones Involved

Level of Hormones Secreted

Cause of Inappropriate Level of Secretion

Symptoms

Treatment

Check your work.

Self-Check Answers

d
a
When you are startled, the adrenal medulla is stimulated by neurons from the sympathetic nervous system to release the hormones epinephrine and norepinephrine. These hormones trigger an increase in breathing rate, heart rate, blood pressure, blood flow to the heart and muscles, and the conversion of glycogen to glucose in the liver. In other words, these hormones trigger all of the “fight or flight” responses. In addition, when the brain detects danger, it signals the hypothalamus to secrete a releasing hormone. The releasing hormone stimulates the anterior pituitary gland to secrete ACTH. ACTH stimulates the adrenal cortex to release cortisol. Cortisol intensifies the responses of epinephrine and norepinephrine, but is longer lasting. Cortisol also increases blood glucose by promoting the breakdown of proteins (amino acids) and fats to glucose (not by conversion of glycogen to glucose like epinephrine and norepinephrine).
The completed table should have the following differences:

Features	Cushing’s Disease	Addison’s Disease
Hormones Involved	Cortisol, aldosterone	Cortisol, aldosterone
Level of Hormones Secreted	Too much	Too little
Cause of Inappropriate Level of Secretion	Tumors in anterior pituitary causing oversecretion of ACTH, OR tumors in adrenal cortex causing oversecretion of cortisol/aldosterone	Destruction of cells in adrenal cortex (autoimmune disease)
Symptoms	Excess accumulation of fat at back of neck (buffalo hump) or in puffiness of the face causing a round or ”moon” face, increased BP and decreased resistance to infections	Sodium ions not balanced, loss of water in urine, low blood glucose, decreased BP,
Treatment	Surgery to remove or radiation to shrink tumors, drugs to dampen effect of ACTH	Cortisol in the form of prednisone or hydrocortisone by mouth in tablet form