Water and Salt Balance

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Water and Salt Balance

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Lecture Note
University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 38 Current Lecture  Response to Changes in Blood Volume and Pressure o o There are 2 different types of baroreceptors in the body  1. In carotid and aortic body- pressure  high pressure arteries  referred to as the “high pressure baroreceptors”  2. Low pressure baroreceptors- blood volume  in low pressure parts of the vascular system  stretch sensitive nerves in the atria, pulmonary blood vessels, and the big veins  these are highly compliant parts of the vascular system  often called volume receptors whereas the high pressure ones are called pressure receptors  Water Balance in the Body o o The water has to be in water balance o Gain and loss of water every day o Main regulated route of water loss= in the urine o No mater how much water one drinks, 99% of that water is reclaimed (proximal tubule and loop of henle and first part of distale tubule)  Osmolarity Within Kidney o o juxtamedullary nephron o kidney has an osmotic gradient where the cortex and the outer medulla have 300mOsM but as you go deeper it gets very highly concentrated due to high amounts of salt and urea o Filtrate in bowmans capsule has the same osmolarity as blood o Descending loop of henle: epithelial cells are permeable to water but not salt  Only water is reabsorbed raising the osmolarity level  Salt cannot follow increasing concentration of salt o Ascending loop of henle: permeable to salt but not water  Salt reabsorbed and osmolarity becomes very low (100)  In the thin part there is little active transport of salt just passive but in the thick part there is more active transport of salt- because not as big of a concentration gradient  Becomes lower than body fluids – 100  Reabsorption of Na+,K+,Cl- in Ascending Limb

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