BCMB 230 1st Edition Exam 4 Study Guide Lectures 20 25 Lecture 20 November 7 There is a lot of glucose in plasma making it easy to supply muscles and brain with energy because cells use it to make ATP However too much plasma glucose can cause osmotic problems It pulls more fluid in with osmotic pressure which decreases ultrafiltration therefore bulk flow does not go out into the tissues We have to be careful with plasma glucose We need a high enough level of glucose for a ready supply of energy but need a low enough level so that it doesn t throw off the pressure in the capillaries Hormones influence plasma glucose regulation They are produced and then put into the blood by the endocrine gland Blood then takes it all over the body through the circulatory system to target cells This pathway allows the source and target cell to not have to be close to each other Certain target cells in different places will then respond to the hormone That target cell however needs a receptor for the hormone Cells that do not have the receptor will not respond Hormones are removed by the kidney or liver so the signals from them are only temporary In order to increase plasma glucose levels eat something sugary with carbohydrates Glucose goes to the pancreas which then produces insulin Receptors for insulin are on most body cells They respond by increasing the amount of glucose that moves from blood into the cell glucose transporters Once glucose moves into the cell this decreases the plasma glucose level to normal Cells can store the glucose as glycogen or use it to make ATP However not all cells have the enzymes to make glycogen Only liver or skeletal muscle can use the process of glycogenesis to produce glycogen from glucose which directly decreases plasma glucose level This maintains the glucose gradient so we can keep moving glucose out of the blood Glycogenolysis is the breakdown of glycogen Gluconeogenesis is the creation of glucose This is inhibited by insulin and does not decrease plasma glucose levels in blood but keeps it from increasing maintains the level Insulin also acts to promote fat storage by taking fatty acids and putting them into fat cells This forces cells to use glucose for energy and not the fatty acids This is a desirable result since we usually have plenty of glucose Insulin also decreases plasma amino acids by forcing ATP production to rely on glucose It moves amino acids into the cells and increase protein synthesis and decrease protein breakdown This cannot happen to all proteins Insulin can also regulate amino acid levels along with glucose in the blood We use a feed forward response to anticipate a change This happens after a meal because the parasympathetic stimulation causes the secretion of insulin In order to decrease plasma glucose levels the plasma glucose level sends a signal to different cells in the pancreas It releases a different hormone called glucagon Glucagon opposes insulin in its action It inhibits glycogenesis promotes glycogenolysis and promotes gluconeogenesis Rather than influence transport of glucose into cells it promotes glycogenolysis and gluconeogenesis which increases glucose levels keeps it from going futher down Glucagon also acts on fat and protein synthesis by promoting the utilization of fats and decreasing protein synthesis in the liver hold off making new proteins to keep plasma amino acids Amino acids are then used to make ATP gluconeogenesis Insulin inhibits the release of glucagon while glucagon inhibits the release of insulin This stops a lot of fluctuation after a meal returning to normal levels of plasma glucose quicker There is a third hormone called somatostatin that is secreted by the pancreas It inhibits GI tract glucose absorption decreasing plasma glucose and also reduces the fluctuation of plasma glucose levels after a meal When there is high plasma glucose somatastatin and insulin is release The three different hormones work together to maintain a fairly high fairly consistent plasma glucose level If blood glucose levels reach above the renal threshold glucose is excreted in the urine High plasma glucose levels are associated with diabetes overindulgence and kidney disease There are other factors hormones situations that influence plasma glucose levels Some things demand more energy such as exercise stress or growth In this situation we need to potentially increase glucose levels However levels do not actually go up because we use up that glucose during that activity Exercise stimulates the adrenal medulla which releases epinephrine increasing plasma glucose levels by promoting glycogenolysis releasing glucose from stores releasing fatty acids mobilizing energy sources Stress stimulates the adrenal cortex and the adrenal medulla releasing cortisol and epinephrine driving the plasma glucose levels up Growth hormones and thyroid hormones can also bring about increases in plasma glucose Lecture 21 November 14 In the urinary system the kidney is the primary organ There are three other structures of the urinary system such as the ureter bladder and urethra These structures handle the weight urine and byproducts of the urinary system The ureter connects the kidney and the bladder The bladder is the muscular sac that holds the urine The urethra is the exit out of the bladder The kidney is located high in the abdominal cavity The top of kidney is above the lowest ribs with the last two ribs coming across the top of the kidney It is embedded fat and held very tightly against abdominal wall and is very well fixed in place in the body There are various layers within the kidney We will look at two the renal cortex and the renal medulla The renal cortex is the outer portion of the kidney where typically everything looks the same homogenous The renal medulla is the inner portion where we see different looking things heterogeneous The nephron is the functional unit in the kidney where work is going on It consists of two kinds of tubes renal tubules and blood vessels that are very closely associated with them In the nephron the glomerular capsule which is also called the Bowman s capsule is the swollen portion that is two layered with space between it called the parietal layer and visceral layer In general anatomical terms parietal means outside visceral means inside The capsular space is continuous with the tube The proximal convoluted tubule is the windy area adjacent to the capsular space In general anatomical terms proximal means