PHGY 210 Lecture Notes - Lecture 5: Fluid Compartments, Osmoreceptor, Extracellular Fluid
15 Feb 2018
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The fluid enters the medullary collecting duct, where the interstitial fluid becomes more and more hyperosmotic, until it reaches the max (1400). Fluid stays hypoosmotic through the whole collecting duct (50). Water excretion is mainly regulated by the rate of water reabsorption from the tubules. Hence, vasopressin is a major regulator of water excretion. Lecture 5 potassium regulation and hydrogen ion regulation. Potassium (k) is the most abundant intracellular ion. The k concentration in the extracellular fluid is extremely important for the function of excitable tissues (nerve and muscle). Reason: the resting membrane potentials of these tissues are directly related to the relative intracellular and extracellular k concentrations. Hyperkalemia: high concentration of k in the extracellular fluid (>5 meq/l) Hypokalemia: low concentration of k in the extracellular fluid (<3. 5 meq/l) Both cause abnormal rhythms of the heart and abnormalities of skeletal muscle contraction. Effect of hyperkalemia on the electrocardiogram precardiac arrest. Dietary intake 90% excreted into urine 10% into feces/sweat.
