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22 Cards in this Set
- Front
- Back
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water
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In the kidneys, what must the walls of the late distal tubules and collecting ducts be made highly permeable to make urine at 1400 mOsm?
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renal tubule
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By varying the degreee of permeability to water in certain portions of the _____ ______, the kidneys can vary the concentration of the urine and the volume of water excreted.
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ADH or vasopressin
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__________ ________ regulates the permeability of the late distal tubules and collecting ducts to water.
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from the post. pit. by neurosecretory cell that originate in the hypothalamus
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Where is ADH secreted from?
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synthesis of aquaporin-2
insertion into the apical membrane of principle cells in the late distal tubules and collecting ducts. |
What does ADH stimulate (2)?
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The apical membrane is impermeable to water, so reabsorption can't occur.
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What happens when there is an absence of ADH?
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water reabsorption
urine volume aquaporin-2 |
_____ _________ and ______ ______ are thus regulated by variations in the plasma levels of ADH, which by determining the number of ____________ pores determines the permeability of the membranes to water: the greater the permeability to water, the greater the water reabsorption.
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in the membrane of cytoplasmic vesicles of principle cells
it awaiting the insertion into the apical membrane in response to ADH |
Where is aquaporin-2 stored and is it awaiting?
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renal tubule
adenylate cyclase cAMP aquaporin-2 |
ADH acts on _____ _____ cells by binding to receptors on the plasma membrane. These receptors are coupled to a g protein that activates the enzyme _________ _______, which then catalyzes the production of the 2nd messenger ______. cAMP activates protein kinase A, which stimulates the insertion of __________ pores into the apical membrane by exocytosis.
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aquaporin-2
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ADH also stimulates the synthesis of new __________ molecules.
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low
high |
At low concentrations of ADH, water reabsorption is ___ and urine output is ____.
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changes in the osmolarity of extracellular fluid
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What is the strongest stimuli for ADH release?
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osmoreceptors
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What monitors the osmolarity of extracellular fluid and are located in the hypothalamus?
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osmolarity
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If the _________of the extracellular fluid increases, then ADH secretion is stimulated and increases water reabsorption.
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osmolarity
inhibited increases |
If the __________ of the extracellular fluid decreases, ADH secretion is _________, which decreases water reabsorption and _________ and water excretion.
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baroreceptors
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Plasma levels of ADH also depend on signals arising in ___________ that detect blood volume and blood pressure.
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Decreased
increases |
__________ baroreceptor activity stimulates increases in the secretion of ADH, which ________ water reabsorption and minimizes the stimuli for the release of ADH.
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kidneys
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If plasma volume decreases below normal, the _______ cannot raise it back to normal; they can only minimize further fluid loss, which then minimizes any additional reductions in plasma volume.
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increased
decreases |
If B.V. and B.P. increases, then ADH secretion decreases, resulting in ________ water excretion, which _________ B.V. and B.P.
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diabets insipidus
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Inadequate reabsorption of water occurs in the desease ________ ________, which is caused by deficiency in ADH secretion from the post. pit. This can be caused by head injury, inflammation of the hypothalamus, or tumors in the hypothalamus or post. pit.
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polyuria
polydipsia |
Because ADH increases water reabsorption, a deficiency in ADH causes excessive urination (_________) and excessive fluid intake (_________) as a compensatory response.
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high
increased |
Diabetes inspidus results in ____ plasma sodium levels and ________ plasma osmolarity.
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