1. Endocrine System

2. Endocrine and Exocrine
Endocrine functions: communication and control, via hormones
Exocrine functions: secrete products into ducts that empty on a surface or into a cavity

3. Endocrine Secretes HORMONES into the blood
Endocrine Organs are located throughout the body: head, neck, chest, abdomen, pelvis.
Endocrine secretions (hormones)bind to specific cells ( target organ cell) that have receptors for that specific hormone.

5. Mechanisms of Hormone Action
Two Major classes of hormones:
Protein & Steroid
Differ in mechanisms by which they influence target cells

6. Protein Hormones
Protein hormones serve as “first messengers”..that is they send message to a specific target organ for functions to take place. Then a number of chemical reactions occur. These reactions activate molecules inside the cell…”second messengers”
Second messengers provide communication within a hormones target cells.

7. Steroid Hormones Pass directly through cell membrane
Enters the nucleus of the cell
Forms hormone receptor complex that acts on the DNA
New protein is formed in the cytoplasm that causes a specific effect in the target cell

8. Regulation of Hormone Secretion
Controlled by homeostatic feedback
Negative Feedback: reverses the direction of change in a physiological system. Ex: Pancreatic Insulin to lower blood sugar
Positive Feedback: amplifies physiological changes. Ex: Oxytocin release during labor to advance birth

9. Endocrine Disease Caused by: Hypersecretion: too much hormone secreted
Hyposecretion: too little hormone secreted.
See Table 10-1, pages