There are four parts to this set. Please type your answers in the text box below
ID: 3514825 • Letter: T
Question
There are four parts to this set. Please type your answers in the text box below, using no more than 250 words for the whole set.
1. Definitions and Concepts:
A) Define osmolality.
B) What are the routes of body water loss, and how much is lost by each per day?
C) What is the distribution of water in the body among the various body fluid compartments expressed as a percentage of body weight?
2.) Describe the mechanisms by which changes in plasma osmolality or changes in mean arterial pressure or blood volume affect the secretion of AVP. What degree of decrease in plasma osmolality and of mean arterial pressure or blood volume are needed to increase AVP secretion?
3.)Describe the cellular mechanisms of action of AVP in the principle cell of the collecting duct
4.) How is urine concentrated and diluted? Incorporate the “single effect”, corticopapillary interstitial osmotic gradient, medullary recycling of urea, diluting segment, and ADH into your answer.
Explanation / Answer
A) Osmolarity is defined as the concentration of solute expressed in Osmol per Liter of solution.
B). Routes of water loss - Urine, sweat, feces, respiration
Daily water loss - 2.3 - 2.6 L/day
C). Distribution of body water
2. Following changes increase AVP release
Most potent stimulus of AVP secretion is change in plasma Osmolarity. Hypothalamus has osmoreceptors that sense any change in Osmolarity. If Osmolarity of plasma is increased then synthesis and secretion of AVP by hypothalamus is increased. AVP is released when plasma Osmolarity reaches around 280 m OsM.
3. AVP act on collecting duct of kidney and increase water reabsorption by increasing synthesis and insertion of Aquaporin or Water channel. This lead to decrease in plasma Osmolarity.
4. Concentration and dilution of urine by ADH (or AVP)
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