BIOL 112 1st Edition Lecture 23 Outline of Last Lecture I Intro to Hormones II Glands III Cellular Response to Hormones IV cAMP Outline of Current Lecture V Feedback Loops VI Insulin VII Glucagon VIII Pathology Current Lecture I 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 regulated by its response directly or indirectly negative feedback two hormones with antagonistic effects insulin and glucagon both are peptide hormones and secreted by the pancreas These 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 facilitated diffusion constant glucose metabolism leads to constant uptake 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 low III Glucagon receptor on target cell surface is a protein which activates a G protein reaction 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 pancreas senses 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 generate glucose for release into blood IV 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 cholesterol 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 pancreases from slaughterhouses now is done with cloned human insulin grown 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 medications
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