1. Chapter 18 The Endocrine System.

2. Endocrine System Overview Uses hormones as control agents Hormones = chemical messengers released into the blood to regulate specific body functions EndocrinologyEndocrinology = the study of hormones and the endocrine organs

3. Nervous System vs. Endocrine System rapid action potentials & neurotransmitters brief slower hormones circulated throughout the body in the blood all body cells exposed; only target cells with receptors respond hormones persist for seconds/hours/days

4. The Chemistry of Hormones 2 main chemical classes of hormones: Proteins Steroids (synthesized from cholesterol)

5. Mechanisms of Hormone Action Changing membrane permeability by opening or closing ion channels Enzyme activation or deactivation Induction or suppression of secretory activities Stimulation of mitosis and meiosis

6. Positive vs. Negative Feedback Positive feedback: “more gets you more” Negative feedback: “more gets you less”

7. Major Endocrine Glands I. Hypothalamus II. Pituitary gland III. Thyroid gland IV. Parathyroid glands V. Pancreas VI. Adrenal glands VII. Gonads VIII. Pineal gland

8. I.Hypothalamus Links the NS with ES Secretes important hormones which are stored and released from posterior Pituitary gland: 1. Oxytocin 2. Antidiuretic hormone (ADH) Both are made in the hypothalamus and released by the pituitary gland.

9. II. Pituitary Gland = “The Master Gland” Stimulates all other endocrine glands Two parts: posterior and anterior Posterior Pituitary: 1. Antidiuretic hormone (ADH) – promotes retention of water by kidneys 2. Oxytocin (OT) – responsible for contractions during labor and milk ejection

10. Anterior Pituitary Gland 1. Growth hormone (GH) – promotes growth 2. Prolactin (PRL) – stimulates milk production 3. Follicle-stimulating hormone (FSH) – stimulates secretion of estrogen, development of follicle cells in ovaries, sperm maturation 4. Luteinizing hormone (LH) – promotes ovulation, secretion of estrogen, progesterone and testosterone 5. Thyroid-stimulating hormone (TSH) – triggers secretion of thyroid hormones 6. Adrenocorticotropic hormone (ACTH) – stimulates production of glucocorticoids

11. III. Thyroid Gland Located under larynx (voice box) Produces thyroid hormones & calcitonin Thyroid hormones - increase metabolic rate, oxygen consumption and body heat production Calcitonin - ↓calcium concentration in body fluids (inhibits osteoclasts and stimulates calcium excretion)

12. Thyroid Gland Pathologies Hypothyroidism Hyperthyroidism – Grave’s disease

13. IV. Parathyroid Glands 4 small glands on the posterior surface of the thyroid gland Produce parathyroid hormone

14. Parathyroid hormone - ↑ calcium concentration in body fluids (stimulates osteoclasts, inhibits osteoblasts, reduces urinary excretion of calcium, & stimulates formation of calcitriol)