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Chapter 10 Lecture Outline page 1 Chapter 10 Endocrine System function: controls and coordinates activity of other organs; maintains homeostasis hormone = chemical messenger carried to target cells by blood endocrine gland = cell or tissue that secretes hormones target cell = cell that has receptors for a given hormone A. chemical classification 1. amino acid derivatives: epinephrine, norepinephrine, thyroid hormones 2. peptides: all hormones secreted by hypothalamus, pituitary gland, heart, kidneys, thymus, digestive tract and pancreas BIOL 2404 Strong/Fall 2006 Chapter 10 Lecture Outline page 2 3. steroids: all hormones secreted by the adrenal cortex and gonads (ovaries and testes) B. how hormones work hormone + receptor → change in cell activity 1. receptor is part of cell membrane (peptide hormones, epinephrine and norepinephrine) hormone binds to receptor enzyme in cell membrane makes second messenger inside cell second messenger causes change in target cell activity a. activates or inhibits intracellular enzymes b. opens or closes membrane channels c. adds new components to cell membrane (receptors, carriers, channels) 2. receptor is located in the cytosol or nucleus (steroid hormones and thyroid hormone) hormone binds to receptor hormone and receptor bind to DNA (chromosomes) and activate one or more genes activated gene causes the formation (transcription and translation) of new proteins which could be enzymes or structural proteins the proteins cause a change in target cell activity C. relationship between hypothalamus and pituitary 1. anterior pituitary gland derived from epithelial tissue, not nerve tissue located inferior to hypothalamus receives hormonal signals from hypothalamus communication between hypothalamus and anterior pituitary occurs through hypophyseal portal system capillaries in hypothalamus BIOL 2404 pick up hypothalamic hormones Strong/Fall 2006 Chapter 10 Lecture Outline page 3 portal vessels capillaries in anterior pituitary drop off hypothalamic hormones 2. posterior pituitary - not really a gland extension of the brain tissue attached to hypothalamus by infundibulum contains axon terminals from two hypothalamic nuclei hormones secreted by neurons in these nuclei are released and diffuse into capillaries in the posterior pituitary D. hypothalamus 1. location – median inferior brain 2. basic structure – individual nuclei 3. hormones and their functions a. regulatory hormones control (increase or decrease) the secretion of anterior pituitary hormones b. antidiuretic hormone (ADH) secreted in response to increased blood osmotic pressure acts on kidneys to conserve water (decreases urine output) released in posterior pituitary gland c. oxytocin secreted in response to uterine contractions, acts on uterine muscle cells to increase contraction strength secreted in response to suckling, acts on contractile cells in mammary glands to expel milk stimulates smooth muscle contraction in ductus deferens and prostate gland (emission is the accumulation of semen before ejaculation) released in posterior pituitary gland BIOL 2404 Strong/Fall 2006 Chapter 10 Lecture Outline page 4 E. anterior pituitary gland 1. location – inferior to hypothalamus; in sella turcica (sphenoid) 2. basic structure – clumps of endocrine cells 3. hormones and their functions a. thyroid stimulating hormone (TSH) – released in response to TRH from hypothalamus; stimulates thyroid gland to release more thyroid hormone b. adrenocorticotropic hormone (ACTH) - released in response to CRH from hypothalamus; stimulates adrenal cortex to release more glucocorticoids c. gonadotropins: follicle stimulating hormone (FSH) and luteinizing hormone (LH) – released in response to GnRH from hypothalamus; stimulate gonads to produce gametes and hormones d. prolactin (PRL) – controlled by hypothalamic hormones; stimulates milk secretion by mammary gland e. growth hormone (GH) - controlled by hypothalamic hormones; stimulates growth, especially in skeletal muscle and cartilage; causes release of stored nutrients into blood F. thyroid gland 1. location – anterior to trachea, inferior to larynx 2. basic structure – a. gross: two lobes, isthmus b. microscopic: follicles are spheres of epithelium filled with colloid 3. hormones and their functions a. thyroid hormone = T3 (triiodothyronine) + T4 (tetraiodothyronine or thyroxine) BIOL 2404 Strong/Fall 2006 Chapter 10 Lecture Outline page 5 produced in colloid inside follicles follicle cells provide raw materials and control TH release TH acts directly on mitochondria to increase ATP production TH causes synthesis of enzymes needed for increased cellular metabolism indirect effects: increased oxygen consumption, increased heat production b. calcitonin secreted by C cells in response to high blood calcium level acts on bone to inhibit osteoclasts acts on kidneys to increase calcium excretion lowers blood calcium level 4. disorders a. hypothyroidism b. hyperthyroidism (goiter is not a disorder, it is a symptom a goiter indicates that the thyroid gland cannot make adequate amounts of thyroid hormone) 5. control of secretion BIOL 2404 TRH hypothalamus TSH anterior pituitary gland TH thyroid gland Strong/Fall 2006 Chapter 10 Lecture Outline page 6 G. parathyroid glands (4) 1. location – embedded in posterior thyroid gland 2. basic structure – chief cells 3. hormones and their functions parathyroid hormone (PTH) secreted in response to low blood calcium level stimulates osteoclasts; inhibits osteoblasts acts on kidneys to decrease calcium excretion acts on kidneys to secrete calcitriol (vitamin D) calcitriol increases intestinal absorption of calcium overall effect is to increase blood calcium level H. adrenal glands (2) 1. location – superior to kidneys 2. basic structure – a. cortex - outer layer produces corticosteroids; 3 zones outer zone secretes mineralocorticoids (aldosterone) middle zone secretes glucocorticoids (cortisol) inner zone secretes gonadocorticoids (androgens and estrogens) b. medulla - modified sympathetic ganglion; chromaffin cells secrete epinephrine and norepinephrine 3. hormones and their functions a. aldosterone secreted in response to low blood sodium level, high blood potassium level, low blood pressure, or low blood volume acts on kidneys to conserve sodium and excrete potassium indirectly maintains body water content BIOL 2404 Strong/Fall 2006 Chapter 10 Lecture Outline page 7 b. cortisol secreted in response to ACTH stimulates release of glucose from the liver stimulates synthesis of glucose in the liver from amino acids and fatty acids stimulates the removal of amino acids from muscle tissue and lipids from adipose tissue overall effect is to increase blood glucose level at abnormally high levels or when used as a drug, has antiinflammatory effects and suppresses immune system c. androgens no major physiological effects at normal levels d. epinephrine and norepinephrine secreted in response to signals from sympathetic preganglionic fibers has same effects as sympathetic nervous system I. pancreas 1. location of pancreas – inferior and posterior to stomach 2. basic structure – a. exocrine tissue = pancreatic acini are primary component of pancreas; secrete digestive enzymes b. endocine tissue = pancreatic islets scattered throughout; alpha cells secrete glucagon beta cells secrete insulin 3. hormones and their functions a. insulin secreted in response to high blood glucose level BIOL 2404 Strong/Fall 2006 Chapter 10 Lecture Outline page 8 acts on target cells by inserting glucose transport proteins into cell membranes causes liver and muscle cells to store glucose overall effect is to decrease blood glucose level causes most cells to turn amino acids into proteins causes adipose cells to store triglycerides as fat tissues that are not insulin targets: liver, kidney cells, CNS b. glucagon secreted in response to low blood glucose level and high blood amino acid level acts on liver and muscle to release glucose into blood acts on liver to make glucose from amino acids and fatty acids overall effect is to increase blood glucose level 4. diabetes mellitus a. type I caused by inability to secrete insulin b. type II caused by inability of target cells to respond normally to insulin (low number of insulin receptors) both types characterized by high blood glucose level normal blood glucose is 100 mg/dL (fasting) and somewhat higher following a meal (140 to 160 mg/dL) above 300 mg/dL glucose is excreted in the urine, causing excess urine output because cells can’t get enough glucose, they have to use other fuels fat is the main alternative fuel and it’s use can lead to a condition called ketoacidosis BIOL 2404 Strong/Fall 2006