Chapter 45: Endocrine System

Learning Targets I can idnetify and explain the role that hormones have in homeostatic pathways. I can diagram how hormones bind to tarfet receptors and trigger specific pathways. I can explain one hormone that displays positive feedback and one that displays negative feedback. I can explain how steriod and peptide hormones differ as ligands in signal transduction pathways. I can explain the significance of having antagonistic hormones to maintain homeostasis.

Steroid vs. water soluble hormones

Short-term stress response and the adrenal medulla (b) Figure 45.21 (a) Short-term stress response and the adrenal medulla (b) Long-term stress response and the adrenal cortex Stress Nerve signals Hypothalamus Spinal cord (cross section) Releasing hormone Nerve cell Anterior pituitary Blood vessel Nerve cell ACTH Adrenal medulla secretes epinephrine and norepinephrine. Adrenal cortex secretes mineralo- corticoids and glucocorticoids. Adrenal gland Kidney Figure 45.21 Stress and the adrenal gland. Effects of epinephrine and norepinephrine: Effects of mineralocorticoids: Effects of glucocorticoids: Glycogen broken down to glucose; increased blood glucose • Retention of sodium ions and water by kidneys • Proteins and fats broken down and converted to glucose, leading to increased blood glucose Increased blood pressure Increased breathing rate Increased metabolic rate • Increased blood volume and blood pressure Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity • Partial suppression of immune system

G protein-coupled receptor GTP Figure 45.7-2 Epinephrine Adenylyl cyclase G protein G protein-coupled receptor GTP ATP Second messenger cAMP Figure 45.7 Cell-surface hormone receptors trigger signal transduction. Protein kinase A Inhibition of glycogen synthesis Promotion of glycogen breakdown

Same receptors but different intracellular proteins (not shown) Figure 45.9 Same receptors but different intracellular proteins (not shown) Different receptors Different cellular responses Different cellular responses Epinephrine Epinephrine Epinephrine  receptor  receptor  receptor Glycogen deposits Figure 45.9 One hormone, different effects. Vessel dilates. Vessel constricts. Glycogen breaks down and glucose is released from cell. (a) Liver cell (b) Skeletal muscle blood vessel Intestinal blood vessel (c)

S cells of duodenum secrete the hormone secretin ( ). Figure 45.11 Pathway Example  Stimulus Low pH in duodenum S cells of duodenum secrete the hormone secretin ( ). Endocrine cell Hormone Negative feedback Figure 45.11 A simple endocrine pathway. Blood vessel Target cells Pancreas Response Bicarbonate release

Hypothalamus/ posterior pituitary Figure 45.12 Pathway Example  Stimulus Suckling Sensory neuron Hypothalamus/ posterior pituitary Posterior pituitary secretes the neurohormone oxytocin ( ). Neurosecretory cell Positive feedback Neurohormone Blood vessel Figure 45.12 A simple neuroendocrine pathway. Target cells Smooth muscle in breasts Response Milk release

Liver, bones, other tissues Figure 45.16 Tropic effects only: FSH LH TSH ACTH Neurosecretory cells of the hypothalamus Nontropic effects only: Prolactin MSH Nontropic and tropic effects: GH Hypothalamic releasing and inhibiting hormones Portal vessels Endocrine cells of the anterior pituitary Posterior pituitary Pituitary hormones Figure 45.16 Production and release of anterior pituitary hormones. HORMONE FSH and LH TSH ACTH Prolactin MSH GH TARGET Testes or ovaries Thyroid Adrenal cortex Mammary glands Melanocytes Liver, bones, other tissues

Figure 45.UN04 Figure 45.UN04 Appendix A: answer to Test Your Understanding, question 9