Module 2

1. Module 2

1.45. Page 5

Lesson 6

Module 2—The Endocrine System

Lesson Summary

In this lesson you investigated the following focusing question:

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

You explored how the nervous and endocrine systems complement and communicate with each other. Your body is like an action-packed emergency room where drama is played out every minute of your life. If you could see 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 pumping 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 co-ordinate and integrate its activities. The release of those thyroxine molecules are stimulated by the release of thyroid stimulating hormone from the anterior pituitary, which is, in turn, regulated by the releasing hormones from the hypothalamus, an important co-ordinating centre in the brain. High levels of thyroxine shut down the releasing hormones and TSH by negative feedback.

The nervous system operates like the speed of the Internet, whereas the endocrine system works more like the regular mail 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, growth and development (of the body and nervous system), reaction of the body to stress, maintenance of ion concentrations (sodium and 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.

Because this is the last lesson in this module and in Unit A, remember to submit the following items:

Module 2: Lesson 6 Assignment
the Module Assessment

Lesson Glossary

There are no glossary terms for this lesson.