BIOL 112 1st Edition Lecture23Outline of Last Lecture I. Intro to HormonesII. GlandsIII. Cellular Response to HormonesIV. cAMPOutline of Current LectureV. Feedback LoopsVI. InsulinVII. GlucagonVIII. PathologyCurrent LectureI. Feedback Loops•control of hormone secretion is regulated by intensity of response•release of hormone causes a response in target tissue•response is monitored by hormone-secreting gland or by other means•response limits further hormone secretion, so that hormone is reg-ulated by its response (directly or indirectly)•negative feedback•two hormones with antagonistic effects - insulin and glucagon•both are peptide hormones and secreted by the pancreasThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.II. Insulin•small protein, two polypeptides held together with disulfide linkages•effect is increase in permeability of plasma membrane to glucose, fa-cilitated diffusion, constant glucose metabolism leads to constant up-take of glucose into cell•after eating a meal, glucose levels in blood increase•pancreas senses increase and releases insulin into circulation•if blood glucose is low, no insulin is released from pancreas•effect of insulin is to decrease blood glucose concentration; in the presence of insulin, tissues take up glucose•liver acts as buffer, absorbs excess glucose from blood and stores it, releases glucose to blood when levels get too lowIII. Glucagon•receptor on target cell surface is a protein which activates a G-proteinreaction to stimulate adenylyl cyclase production of cAMP•target tissue is liver•when stimulated with glucagon, liver cells hydrolyze glucose and release into blood•when blood glucose levels drop (during a fast, for instance), pancreassenses decrease and releases glucagon into circulation•If blood glucose is high, no glucagon is secreted•target cells are liver cells, consume their glycogen reserves and gen-erate glucose for release into bloodIV. Pathology•excessively high glucose levels overwhelm ability of kidney nephrons to recover glucose to blood•therefore, glucose is shed into urine (which isn’t normal) and excess osmotic loss of glucose also leads to water loss, so individual makes excessive volumes of urine which contains glucose•Untreated, this causes several problems:•loss of glucose in urine•dehydration from excess water loss in urine•weakness because muscles are chronically starved for glucose (can’t remove glucose from blood)•mobilization of fats into blood, leading to excessively high choles-terol levels•Treatment?•Replace missing insulin by daily injections of prepared insulin•Diabetic must monitor food intake, blood glucose concentration and insulin injections to maintain proper balance•Used to be done with animal insulin (cow or pig) isolated from pan-creases from slaughterhouses, now is done with cloned human insulingrown in bacteria•Type II Diabetes•genetic factor•expression can be brought on by overweight and diet•this is insulin insensitive diabetes•problem is loss of sensitivity to insulin by target tissues•accounts for over 90% of all diabetes in US•Can be managed by diet, weight control, exercise, and some
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