Physiology Final Review

Physiology Final Review - Physiology Final Review Lecture...

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Physiology Final Review Integrates several systems o Overlap in functions and so change made in one system affects others o Decrease in blood volume and blood pressure triggers homeostatic reflexes in cardiovascular system and kidneys, as well as behavior Water balance o o Metabolic water is produced as a product of oxidation of nutrients o Loss: urine o Water loss via skin and lungs is about 2/3 of urine water loss (“insensible” because we aren’t usually aware of it) Can be significant with excessive sweating or diarrhea o Problems with too little water Volume depletion of the extracellular compartment decreases blood pressure. (< Blood pressure = inadequate oxygen to tissues) Hyposmotic fluid is lost (excessive sweating), the solutes left behind in the body raise osmolarity, potentially disrupting cell function o Problems with too much water o Kidneys only conserve water, not produce Osmolarity of body fluids affected by solutes AND water o If body fluids are already at the target OsM, urine produced in isosmotic wrt current body fluids o If body fluid is hyperosmotic, urine produced is concentrated and hyperosmotic o If body fluid is hyposmotic, urine produced is less concentrated and hyposmotic. Mechanism for production of hypo- and hyper-osmotic urine o Final urine range: 50-1200 mOsM (depends on body OsM and water balance) o Final adjustment of urine osmolarity takes place at END ( primary collecting duct ) o Osmotic gradient occurs within the MEDULLA (Is maintained by blood flow pattern) o Descending limb of loop of Henle is PERMEABLE to water (so water OUT) Fluid leaving proximal tube gets more concentrated
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o Ascending arm of loop of Henle is impermeable to water, so water does not move in or out as ions are transported out of lumen of nephron Removal of solutes in the thick limb creates hyposmotic fluid o Permeability of collecting duct (to water) is controlled by hormones Vasopressin : (ADH—anti-diuretic hormone) Hormone released by posterior pituitary Causes increase in collecting duct permeability to water o So water moves out of nephron making urine more concentrated [higher OsM] Permeability to water is generated by insertion of aquaporins in cell membrane of nephron cells (lumen side)[apical membrane] In the absence of vasopressin, the urine is dilute (hyposmotic) The water pores are withdrawn from apical membrane by endocytosis and stored in cytoplasmic vesicles Factors affecting vasopressin release o OsM > 280 mOsM**** most important o Decreased atrial stretch (due to low blood volume) o Decreased blood pressure o Factors that stimulate vasopressin release are related to water conservation need of body Salt Balance o Active reabsorption of ions in the thick ascending limb creates a dilute filtrate in the lumen o Water balanced in descending and ascending arms of loop of
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This note was uploaded on 06/05/2010 for the course BIO SCI E109 taught by Professor Briscoe,a during the Fall '08 term at UC Irvine.

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Physiology Final Review - Physiology Final Review Lecture...

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