1. Hormones and the Endocrine System
Chapter 45

2. YOU MUST KNOW
How hormones bind to target receptors and trigger specific pathways
The secretion, target, action, and regulation of at least two hormones
An illustration of both positive and negative feedback in the regulation of homeostasis by hormones

3. I. Secretion & Response
Endocrine system is all hormone-secreting cells and tissues
1. Endocrine glands – no ducts, secrete hormones directly into the body fluids
2. Hormones – chemical signals that cause a response in target cells

4. Target cell receptors
1. Cell-surface receptors – at the cell membrane, binding of hormone causes signal transduction pathway
Ex. epinephrine binding to liver cell causes conversion of glycogen to glucose

5. 2. Intracellular receptors – found within the cell (require lipid-soluble hormones), receptor-hormone complex acts as a transcription factor affecting gene expression Ex. Testosterone stimulates expression of specific genes

6. Receptors can be on one tissue, multiple tissues, most tissues, or other endocrine glands (tropic hormones)
a. Hypothalamus – coordination between nervous & endocrine systems

7. b. Posterior pituitary – stores and releases hormones made by the hypothalamus -Oxytocin – causes uterine contractions during childbirth and ejection of milk during nursing -Antidiuretic hormone (ADH) – target cells are collecting ducts of kidneys, makes them more permeable to water so that more water is reabsorbed back to the body instead of exiting in urine

8. Anterior pituitary – synthesizes & secretes hormones, many tropic,
-Follicle-Stimulating Hormone (FSH) – stimulates gametogenesis (formation of eggs & sperm)
-Luteinizing Hormone (LH) – triggers ovulation and production of testosterone