Endocrine system is about "hormones."

Hormones are sometimes called "messengers." 

Hormones are usually: 

• secreted by a gland (group of special cells that manufacture and release substances)
• travel in the blood to a target tissue or organ
• stimulate target to do some action (ie. very specific because only certain cells have "receptors" for the hormone.)

For example:  When you eat food, the carbohydrates in the food are broken down into smaller pieces called sugars.  These sugars enter your blood and the sugar level (concentration) of your blood increases.  When the sugar level in your blood increases, this stimulates the pancreas (organ) to secrete insulin (hormone).  The insulin travels throughout your body in your blood stimulating your muscles and your liver to "absorb sugar."  In other words, insulin acts like a chemical message saying, "Absorb sugar!"

It is important to know that in general, hormones are produced and secreted in one location but they have an affect on a different part of the body in a different location.

Examples of hormones include:  insulin (pancreas), testosterone (testes), estrogen (ovary), progesterone (corpus luteum), gastrin (stomach), epinephrine (adrenal), follicle stimulating hormone (pituitary), leutenizing hormone (pituitary) and many others.

Hormones are made of several materials, the most common being lipids (like estrogen and testosterone), and proteins (like insulin).

Next we will study the functions of hormones:

1. Reproduction 
2. Development and growth
3. Homeostastis
4. Metabolism

Assignment

Go to to the quia website, go to Anatomy11 class and click on Hormones (introduction).  Complete the fill-in-the-blank exercises.  The terms come from your textbook or notes in class.