The Endocrine System!

What is it? It is the system of glands that make the hormones that influence our body functions. There are quite a few glands, and each one makes specific hormones. Some of the hormones that these glands make directly affect our body tissues in ways with which we are familiar-- like by stimulating bone growth or by stimulating egg maturation within an ovary. Other hormones have subtler effects, like regulating water loss and blood ion concentrations. Still other hormones strictly function to regulate the release of other hormones.

This unit is all about how hormones affect our bodies. Hormones are officially defined as chemicals that travel in our blood to affect distant tissues. The reason that "travel in our blood" is typically specified is because blood circulation enables hormones to be carried all over our bodies; this way, hormones can affect distant and nearby tissues equally (by distant, that means distant from the gland producing the hormone).

Therefore, how does a chemical (a hormone) affect the cells & tissues of the human body? And how do chemicals affect other chemicals (one hormone can influence the release of another hormone)?

I have broken this unit down into the following sections for you:

Hormones have many chemical forms

Hormones must bind to receptors to cause an effect

	How steroid hormones work
	How non-steroid hormones work

Regulation of hormones

Endocrine Glands and their hormones

The Hypothalamus & the Pituitary Gland
These regions act as the "master" endocrine glands. Their hormones mainly function to regulate the release of other hormones

Other endocrine glands:

	The thyroid gland
	The parathyroid glands
	The adrenal gland: * adrenal medulla * adrenal cortex
	the pancreas, pineal gland & others

Stress and the endocrine system

As you look through the above list, you should notice that the first two major headings ("Hormones have many chemical forms" & "Hormones must bind to receptors...") both deal with the chemical and cellular mechanisms of hormone action. The "regulation of hormones" section deals with the concept of how and why some hormones affect other hormones. Only after understanding that are you ready to begin to learn about the glands and the hormones they produce. Therefore, the next two major headings are about the glands and their hormones, and each set of pages will describe how each hormone acts on the cells and tissues of the body. Finally, we'll wrap this week up by learning a bit about how stress affects the body through the endocrine system.

After you begin working on this unit and learn about the cellular and chemical actions of hormones, you'll find that the number of glands and hormones seems overwhelming. There really are a lot of hormones to keep straight. My advice to you is for you to truly memorize exactly which glands make which hormones. You see, there are so many hormones, and they have so many effects (including regulating each other) that if you don't memorize which hormone comes from where, you will not be able to keep all the rest of the details straight! On the web page introducing the glands themselves, I have included a table to try to summarize all the glands and their hormones. I hope it helps.