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68 Cards in this Set
- Front
- Back
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major anabolic hormone
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insulin - promotes storage of nutrients in liver, muscle, adipose cells; synthesis of proteins
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major counterregulatory hormone
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glucagon - mobilizes fuel reserves
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paracrine actions of insulin
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suppresses glucagon release from alpha-cells
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where is proglucagon produced
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in alpha cells of pancreas and L cells of intestine
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half-life of pancreatic glucagon
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~3-6 minutes; removed by liver and kidney
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where is somatostatin secreted
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hypothalamus, D-cells of pancreatic islets, CNS, gastric and duodenal mucosal cells
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potency of different somatostatins
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SS-28 (gut) is 7-10 times more potent than SS-14 (hypothalamus, CNS, and pancreas)
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tolbutamide
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sulfonylurea drug that increases insulin secretion, also increases secretion of pancreatic somatostatin
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what metabolites increase somatostatin release
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glucose, arginine, and leucine
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hormones that increase somatostatin secretion
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glucagon, vasoactive intestinal peptide (VIP) and CCK (insulin doesn't affect directly)
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How many receptors have been found for somatostatin and do they care which one binds
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5; four of them have no preference
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what happens when somatostatin receptors are activated
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inhibitory G-proteins of adenylate cyclase - reduces cAMP and protein kinase A is not activated
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overall somatostatin fxn
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inhibit secretion of many hormones; slow down GI emptying (via gastrin inhibition)
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octreotide
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analog of native somatostatin resistant to degradation; half-life of 110 minutes
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pegvisomant
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GH-receptor antagonist
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where is the gene for GH located
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chromosome 17
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structurally similar hormones to GH
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human prolactin and human chorionic somatomammotropin (hCS)
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what proteins does GH cause an increase in in hepatocytes
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IGF-1, alpha2-macroglobulin, serine protease inhibitors Spi 2.1 and Spi 2.3, and ornithine decarboxylase
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what is ornithine decarboxylase involved in
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enzyme active in polyamine synthesis (regulation of cell proliferation)
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GH receptors of muscle and adipocytes
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cytoplasmic tyrosine kinases for signal tranduction
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where is GHRH exclusively produced
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cells of the arcuate nucleus
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what intracellular mechanisms stimulate GH release
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cAMP and calcium-calmodulin both
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GH affect on adipose tissue
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increases sensitivity to lipolytic action of catecholamines and decreases sensitivity to lipogenic action of insulin
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what do the two somatomedins in humans share a structural homolog with
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proinsulin
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insulin-like growth factor I alternative names
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human IGF-I or somatomedin C
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insulin-like growth factor II alternative names
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human IGF-II or somatomedin A
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intracellular portion of plasma membrane receptor for IGF-I
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intrinsic tyrosine kinase activity
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IGF-II and GH
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independent of GH levels in blood
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precursor of catecholamines
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tyrosine
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symptoms of catecholamine excess
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excessive sweating, palpitations, tremulousness, hypertension, throbbing headache, glucose intolerance long term
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how can a diagnosis of pheochromocytoma be made
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measure urine catecholamine levels or their metabolites (metanephrines and vanillylmandelic acid (VMA))
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adrenergic receptor types
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alpha and beta
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catecholamine effects on cardiovascular system
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increase cardiac output and systemic BP
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catecholamines and receptor binding
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bind loosely (low affinity) and disassociate quickly causing duration of biologic response to be brief
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major physiologic glucocorticoid in humans
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cortisol (hydrocortisone)
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what neurotranmitters stimulate synthesis and release of corticotropin releasing hormone (CRH)
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acetylcholine and serotonin
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where is CRH released
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hypothalamico-hypophyseal portal blood
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what cells in the anterior pituitary does CRH stimulate
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corticotrophs (secrete ACTH)
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major trophic influence of ACTH on cortisol synthesis
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conversion of cholesterol to pregnenolone
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steps in thyroid hormone synthesis
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1) transport/trapping of iodide from blood into acinar cells 2) oxidation of iodide 3) iodination of tyrosyl residues on thyroglobulin to form iodotyrosines 4) coupling of residues of mono and di-iodotyrosine into thyroglobulin to form T3 and T4 residues
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T4 de-iodinated at 5' position forms
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T3
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MIT
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3'-monoiodotyrosine residue
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MIT and DIT coupling forms
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T3 residue
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Two DIT residues form
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T4 residue
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under most circumstances what is the T4/T3 ratio in thyroglobulin
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~13:1
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plasma half-life of T4 and T3
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~7 days and ~ 1-1.5 days respectively
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what does TSH cause in the thyroid
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endocytosis of thyroglobulin to form endocytic vesicles within thyroid acinar cells; causes all phases of thyroid hormone synthesis by thyroid gland to be stimulated
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what occurs to endocytic vessels of thyroglobulin
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fuse with lysosomes which hydrolyze thyroglobulin releasing T3 and T4
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main hormone that negatively regulates TSH secretion
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T3
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TSH secretion pattern
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circadian; surge late afternoon and before onset of sleep; intervals of 2-6 hours btwn peaks
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what ratio are T4 and T3 released in
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T4:T3 ratio is 10:1; T3 is active form, T4 is converted in tissues to T3
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what intracellular mechanisms does TSH cause in acinar cells of thyroid
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cAMP, also inositol triphosphate and diacylglycerol (causes rise in intracellular Ca2+)
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where is thyroglobulin stored
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extracellularly in colloid that fills central space of each thyroid follicle
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thyroid hormone and the liver
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increases glycolysis and cholesterol synthesis and increases conversion of cholesterol to bile salts; increases sensitivity to epinephrine (indirectly increasing glucose production)
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how does TH indirectly increase flow of fatty acids to liver
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sensitizes adipocytes to lipolytic activity of epinephrine - increases liver triacylglycerol synthesis
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major determinant on rate of lipogenesis
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amount of glucose and insulin available to adipocyte: T3 has amplifying/facilitory affect
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T3 and muscle
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increases glucose uptake, stimulates protein synthesis; sensitizes to glycogenolytic actions of epinephrine
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thyroid and pancreas
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increases sensitivity of B-cells to those that promote insulin release; require for optimal insulin secretion
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T3 and cold temperature
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sensitizes sympathetic nervous system to stimulatory effect of cold exposure
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what does T3 stimulate in sympathetic nervous system with cold exposure
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increase release of norepi which stimulates uncoupling prootein thermogenin in brown adipose tissue resulting in increased heat production for uncoupling of oxidative phosphorylation
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Motilin is secreted from where
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enteroendocrine M-cells of proximal small bowel
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motilin fxn
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stimulates gastric and pancreatic enzyme secretion
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pancreatic peptide (PP)from pancreatic islets fxn
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reduces gastric emptying and slows upper intestinal motility
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Peptide YY cells from alpha cells
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inhibits gastric acid secretion
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secretin from enteroendocrine S-cells in proximal small bowel fxn
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regulates pancreatic enzyme secretion and inhibits gastrin release and secretion of gastric acid
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what stimulates glucagon release in vivo
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CCK and gastrin
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insulin secretion and nerve fibers
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increased secretion via vagus and supressed by sympathetic alpha-adrenoceptors
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iatrogenic Cushings
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due to synthetic administration of glucocorticoids
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