ANIMAL PHYSIOLOGY
OSMOREGULATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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release MORE ADH, making the collecting duct MORE permeable
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release LESS ADH, making the collecting duct LESS permeable
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release MORE ADH, making the collecting duct LESS permeable
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release LESS ADH, making the collecting duct MORE permeable
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Detailed explanation-1: -Dehydration causes the hypothalamus to release ADH (antidiuretic hormone) via the posterior pituitary gland. The ADH signal tells the kidneys to recover water from urine, which dilutes the blood plasma.
Detailed explanation-2: -There are two major stimuli for ADH release: elevated plasma osmolality and decreased effective circulating volume. Increased plasma osmolality causes shrinkage of a specialized group of cells in the hypothalamus called osmoreceptors.
Detailed explanation-3: -ADH molecules bind to receptor proteins, activating a signalling cascade that leads to the phosphorylation of the aquaporin molecules. This activates the aquaporins, causing the vesicles to fuse with the luminal membranes of the collecting duct cells. This increases the permeability of the membrane to water.
Detailed explanation-4: -A high ADH level causes the body to produce less urine. A low level results in greater urine production. Normally, the amount of ADH in the body is higher during the night. This helps prevent urination while you are sleeping.