Endocrine+System

=**1. Compare the operations of the nervous system and the endocrine system.**=


 * Both help to maintain homeostasis through regulation.
 * The nervous system responds quicker than the endocrine system.
 * The endocrine system is the longest lasting of the two systems.
 * The nervous system sends chemical messages to the endocrine system to initiate production and secretion of hormones.

=**2. Define the two types of hormones**=


 * Protein – type hormones **
 * Cannot penetrate the cell membrane Ex. insulin
 * Utilize the two messenger model of hormone action
 * Hormone combines with a receptor, which activates enzymes within the cell.
 * These enzymes produce a compound which acts as a second messenger, diffusing into the cell to produce the effect.


 * Steroid – type hormones **
 * Lipid-like; Can pass through the cell membrane Ex. estrogen
 * Utilize the one messenger model of hormone action
 * Hormones enter most of the cells but produce their effect only in target cells.
 * When the hormone binds to a receptor protein that recognizes it, the hormonal effect is produced.

=**3. Explain Feedback.**=
 * The rate of hormone secretion varies with the needs of the body.
 * ** Positive feedback **is when the feedback reinforces the original change.
 * Ex. Increase in A, causes an increase in B. This causes a further increase in A.


 * ** Negative feedback ** is when hormones flow in such a way as to counteract the current cell activity.
 * Negative feedback is when the feedback opposes the original change.
 * Most glands are regulated by negative feedback because it maintains homeostasis.
 * Negative feedback is when the feedback opposes the original change.
 * Ex. Increase in A, causes an increase in B. The increase in B causes a decrease in A.

=**4. A Diagram of the Endocrine Glands**= = = =**6. Endocrine Gland Hormonal Secretions**=