Test 4 summary - Test 4 Material Urination...

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Test 4 Material Urination Nephron— functional unit of the kidney with a vascular and a filtration system. Everything but cells and proteins in the blood can be filtered through pores, most of it is reabsorbed Inulin— a large fructose polymer that is filtered by the kidney but not reabsorbed, metabolized, and secreted. Used to measure glomerular filtration rate (GFR) to test urinary system. Transport maximum— limit of transport of molecules due to limited umber of carriers. For glucose the maximum is 300mg/100mL, which is 3x more carriers than needed (normally 100mg/100mL) o Glucosuria— glucose in urine, a sign of diabetes. Blood has 3x more glucose than normal so not all of it is being transported by a carrier. Glucose attracts water so you also lose extra water Sodium reabsorption— controls reabsorption of many other molecules including water. Sodium pump is only on the basolateral side of cells and creates a gradient from filtrate ISF plama. ATP is needed for energy and tight junctions prevent flow in spaces in between cells. Important in maintaining BP. Caffeine decreases sodium reabsorption and works as a diuretic because less water is also reabsorbed. Renin-Angiotensin system— maintains BP by increasing sodium and water reabsorption. If there is a decrease is renal BP there is a release of renin from the kidney’s JG cells which surround the glomerulus. Renin is a protease and splits Angiotensinogen from liver into angiotensin I. o Production of angiotensin II— renin converts angiotensinogen into angiotensin I. Angiotensin converting enzyme (ACE) in the walls of the lung capillaries converts AI AII. o Effects of Ang II— a powerful vasoconstrictor which increases BP. It also causes the release of aldosterone from adrenal cortex, which increases blood pressure and stimulates further reabsorption of sodium and water. Loop of Henle— creates an osmotic gradient in kidney medulla. At the cortex, it is 300mOsm and 1200mOsm in deep medulla. It regulates the concentration of blood and urine. Filtrate at the end of it is 100mOsm and plasma is 300mOsm. Vasopressin— from posterior pituitary, it is responsible for controlling urine osmolarity. If the plasma osmolarity is high (>300mOsm) it is released and causes a production of proteins and aquaporins in the collecting duct membrane. This allows water to move easily to ICF to leave the body. o Aquaporins— water channels. Water goes through aquaporins. Osmotic pressure of solutes in the medulla draws water in and retains it. Urine may go up to 1200mOsm. Aldosterone effects— produced by adrenal gland, responsible for controlling urine volume. Increased umber of active sodium carriers on luminal side of collecting duct causes increased reabsorption of sodium in collecting duct with water following osmotically. Long-term BP regulator. Potassium reabsorption is reciprocal to sodium.
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