phystut5a - Renal System : Part 3 Andrew MacDonald November...

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Renal System : Part 3 Andrew MacDonald November 12th, 2009
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Regulation of Water Balance The more you drink the more you urinate! If you drink and excess or an increased amount of fluid, you will produce a large volume of dilute urine. If you drink very little or a small volume of fluid then you will produce a very small volume of concentrated urine.
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Salt and Water Balance in Humans Humans can regulate salt and water balance separately . This simply means that there is not a exact correlation between the amount of water and salt lost.
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Regulation of Water Balance Water Balance depends on the intake and output of water. Intake We attain most of our water through the intake of food and fluids (ie. Eating celery or drinking juice). Output (water is lost in several ways) Urine Skin Lungs Feces Sweat.
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Regulation of Water Balance (ADH) Anti-diuretic Hormone (ADH) It is also known as vasopressin. It is a peptide hormone that is made in the hypothalamus and then stored in the posterior pituitary gland It causes an increase in water reabsorption in the collecting duct (highly regulated section of the tubule). It’s release is stimulated by dehydration. Remember that, diuresis describes an increase in urination. Thus, anti- diuretic hormone causes a decrease in urination.
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Regulation of ADH Release There are two primary mechanisms that detect dehydration within the body that cause the release of ADH. 1) Osmoreceptors in the hypothalamus 2) Baroreceptors in the carotid arch and aortic sinus The osmoreceptors sense changes in the osmolarity of the plasma. Generally, a higher osmolarity indicates dehydration while a lower osmolarity indicates excess water. The baroreceptors ( pressure receptors) sense changes in blood pressure and the ECF volume.
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Regulation of ADH Release 1) Osmoreceptors located in the hypothalamus , detect changes in plasma osmolarity. When plasma osmolarity is high, the hypothalamus will be stimulated to release ADH. When plasma osmolarity is low, the hypothalamus will not be stimulated to release ADH. 2) Baroreceptors are located in the aortic sinus and carotid arch. An increase in ECF volume and blood pressure increase
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Baroreceptors! Water Loss, Plasma Osmolality Osmoreceptor volume ADH Released Water levels conserved OSMORECEPTORS BARORECEPTORS If the osmolarity of the plasma is 275 mOsm, will ADH be released? No, this would
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phystut5a - Renal System : Part 3 Andrew MacDonald November...

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