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Unit IV: Regulation Endocrine System II Chapter 16 pp. 552 - 573 Thyroid Gland • High blood flow per gram of tissue Thyroid Gland • Thyroid follicles (follicular cells) – Two hormones: • Triiodothyronine (T3) and Thyroxine (T4) – thyroid hormones • body’s metabolic rate and O2 consumption • calorigenic effect - heat production • heart rate and contraction strength; respiratory rate • stimulates appetite and breakdown CHO, lipids and proteins • C (calcitonin) cells – calcitonin that blood Ca2+ , promotes Ca2+ deposition and bone formation Parathyroid Glands • PTH release in response to hypocalcemia – blood Ca2+ levels – Mechanisms: 1. promotes synthesis of calcitriol in kidneys 2. re-absorption of Ca2+ and urinary excretion 3. bone resorption osteoclasts 4. collagen synthesis by osteoblasts bone deposition Adrenal Gland (Suprarenal) • Arises from two different fetal glands Capsule Cortex Medulla Capsule Zona Glomerulosa Zona Fasciculata Zona Reticularis Adrenal Medulla Adrenal Medulla • Sympathetic ganglion innervated by sympathetic preganglionic fibers – catecholamines (epinephrine, NE) • Hormonal effect to stress is longer lasting – Increases alertness, anxiety, or fear – increases BP, heart rate and air flow – Increased sweat gland activity – raises metabolic rate • inhibits insulin secretion • stimulates gluconeogenesis and glycogenolysis • Stress causes medullary cells to stimulate cortex Adrenal Cortex • Corticosteroids – Aldosterone / mineralcorticoids • control electrolyte balance promotes Na+ retention and K+ excretion – Cortisol / glucocorticoids (hydrocortisone) • stimulates fat and protein catabolism, gluconeogenesis and release of fatty acids and glucose into blood • anti-inflammatory effect – sex steroids • androgen (DHEA testosterone) • estrogen (important after menopause) Pancreas Pancreas • Insulin (70%, beta cells) – secreted during/immediately after a meal when blood glucose and amino acid levels rise – stimulates glucose and amino acid uptake – nutrient storage effect blood glucose level • Glucagon (20%, alpha cells) – secreted between meals when blood glucose levels fall – stimulates glycogenolysis, release of FFA’s, and promotes absorption of amino acids for gluconeogenesis glucose level • Gastrin stimulates stomach acid secretion, motility, and emptying also secreted by stomach and small intestine Notes • Hyperglycemic hormones raise blood glucose – Glucagon, GH, epinephrine, NE, cortisol and corticosterone • Hypoglycemic hormones lower blood glucose – insulin Gonads Ovaries and Testes • Estradiol and Progesterone − Development of female physique − Development of female reproductive system • Testosterone − Development of male physique − Development of male reproductive system • Inhibin − Suppress FSH secretion Endocrine Functions of Other Organs • Heart – – atrial natriuretic peptide (ANP) – blood volume and BP by Na+ and H2O loss by kidneys • Liver – Erythropoietin (EPO) 15% – angiotensinogen • precursor of angiotensin II – IGF-I – Hepcidin – promotes intestinal absorption of iron – role in making calcitriol Endocrine Functions of Other Organs • Kidneys – Erythropoietin (85%) – Role in making Angiotensin II – Calcitriol (active form of vitamin D) • more blood Ca2+ available for bone deposition • Stomach and small intestines – enteric hormones coordinate digestive motility and secretion – CCK, Gastrin, Ghrelin, Peptide YY • Placenta – secretes estrogen, progesterone and others • regulate pregnancy, stimulate development of fetus and mammary glands