Quiz 8 Study Guide What two kinds of cues can trigger thirst Hypovolemic Thirst reduced extracellular volume Osmotic Thirst high extracellular solute concentration What are 2 functions of vasopressin when body fluids are low What is its other name What is diabetes insipidus Reduces fluid loss at the kidney by inserting aquaporins in the collecting ducts of the kidneys Constricts blood vessels and the formation of angiotensin II which acts on the brain to trigger thirst constricts blood vessels and stimulates vasopressin release Vasopressin aka ADH antidiuretic hormone Diabetes insipidus no vasopressin kidneys retain less water chronic thirst What is hypovolemia and why is it dangerous How is it detected by the body Release of vasopressin a k a antidiuretic hormone ADH from posterior pituitary blood vessel constriction and increases water retention by the kidney Baroreceptors in blood vessels and the heart detect the initial drop Why is it necessary for the kidney to have sufficient blood pressure Kidneys need enough blood pressure to squeeze plasma out of blood vessels to form urine excrete metabolic waste Summarize briefly how the kidney works The kidney filters and conserves body fluid It requires sufficient blood pressure to extrude plasma out of the capillaries in the glomeruli That plasma would be lost as urine if it is not reabsorbed back into the body Cells lining the loop of Henle in the kidney pump Na out of the fluid and back into tissue around the loop Cl follows Na passively due to electrical attraction Water follows passively due to osmosis The water passes through aquaporins small channels in the collecting ducts of the kidney 99 of filtered fluid is conserved in this way What leads to the production of angiotensin II and what are 2 of its main effects What are 2 brain areas that respond to angiotensin II When blood volume is low the kidney releases renin Renin converts angiotensinogen to angiotensin I which is converted to angiotensin II by angiotensin converting enzyme ACE 2 main effects Constricts blood vessels conserves water Releasing vasopressin and aldosterone 2 brain areas Subfornical organ and preoptic area What is osmotic pressure What happens if you pour salt into one side of a container that is separated from the other side by a semipermeable membrane Osmotic pressure moves water across a membrane along its concentration gradient Water flows through the membrane equalizing the solute concentrations and shrinking the cell salt can t cross the membrane What is the major role of the OVLT in osmotic thirst OVLT a brain area adjoining the 3rd ventricle Why is it beneficial to have enough salt in the body in order to respond to hypovolemia What hormone promotes Na conservation Salt is needed to maintain water in the extracellular compartment important for fluid balance Aldosterone What is the effect of insulin on blood glucose What is the effect of glucagon Insulin regulates the process of converting glucose to glycogen Glucagon another pancreatic hormone glycolysis converts glycogen back into glucose when blood levels drop Why do people with untreated diabetes I eat a lot but gain little weight Their pancreas stops producing insulin No insulin no fat storage Where is leptin produced Why can t we treat most obese people with leptin Leptin is released from fat cells in adipose tissue and secreted into bloodstream Because most obese people lack either the leptin receptor or leptin itself What is the evidence that the lateral hypothalamus LH is important for hunger Lateral hypothalamus LH lesions caused aphagia refusal to eat it was identified as a hunger center What behavioral changes are produced by lesions of the ventromedial hypothalamus VMH VMH lesioned animals exhibit a dynamic phase of obesity with hyperphagia overeating until they become obese They are also finicky eat only palatable food Why do we not think that animals with VMH lesions are simply ravenously hungry all the time It isn t so much that the rats are getting fat because they are eating too much they are eating too much because they are getting fat What is the function of the paraventricular nucleus PVN in controlling eating What nucleus controls the PVN Integrate appetite signals modulate food intake NPY AgRP neuropeptide Y and agouti related peptide Arcuate nucleus What is leptin Which brain nucleus responds to leptin Leptin activates POMC CART neurons but inhibits NPY AgRP neurons so leptin suppresses hunger Arcuate nucleus of the hypothalamus When and where is ghrelin produced What is its effect on feeding Ghrelin is released into the blood by endocrine cells in the stomach Besides stimulating growth hormone release where it gets its name ghrelin is an appetite stimulant Ghrelin increases the release of glucose from the liver however that glucose can t be used for growth unless somatomedin is also released from the liver If someone is hungry somatomedin is not released Therefore the glucose metabolism Levels of ghrelin rise during fasting and fall after a meal except in obese subjects they remain high Ghrelin and PYY3 36 acting mainly on NPY AgRP neurons work in opposition to provide short term appetite control Ghrelin stimulates the cells leading to an increase in appetite What is one physiological way in which lesions of the VMH promote obesity and one way in which the LH contributes to feeding Higher set zone for weight Lower set zone for weight What is the effect of alpha MSH on hunger How about neuropeptide Y NPY How about endocannabinoids MSH inhibits the LH s appetite stimulating activity resulting in less feeding NPY AgRP neurons activate the PVN and LH increasing feeding Endocannabinoids homologs of marijuana increase appetite and feeding What are some possible treatments for obesity Leptin for a tiny minority who lack it Most have lots of leptin but have insensitive receptors for it Cannabinoid antagonists Alpha MSH agonists also prosexual Certain thyroid agonists Angiogenesis inhibitors Reducing fat absorption bad side effects Reduced reward Anti obesity surgery gastric bypass fat removal Compare the symptoms of anorexia nervosa with those of bulimia nervosa and binge eating Anorexia Refusal to maintain body weight BW at or above a minimally normal weight for age and height BW 85 of normal BMI 17 5 kg m2 Intense fear of gaining weight or becoming fat Disturbance of body image Amenorrhea primary or secondary Bulimia Marked by periodic gorging and purging by vomiting or