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31 Cards in this Set
- Front
- Back
What kind of sensors/receptors detect changes in sodium balance?
Where are they located? |
Baroreceptors (volume-dependent receptors)
*Afferent arterioles, carotid sinus, aortic arch, and right atria |
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List 4 major effectors of the volume regulatory pathway.
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1. Renin-angiotensin-aldosterone
2. Atrial natriuretic peptide 3. ADH 4. Norepinephrine |
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Which portion of the extracellular fluid compartment is sensed by the baroreceptors?
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Plasma volume
(effective circulating volume) |
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How does GFR affect sodium excretion?
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Increases in GFR increase sodium excretion, decreases in GFR decrease sodium excretion
|
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What is direct the function of Angiotensin II on the nephron?
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Stimulates the Na+-H+ exhcanger in the proximal tubule
(increases sodium reabsorption) |
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Which substances stimulate the Na+-H+-exchanger in the proximal tubule?
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1. Angiotensin II
2. Norepinephrine |
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What is the most important site on the nephron for the regulation of sodium reabsorption?
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Distal tubule and collecting duct
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What are the actions of aldosterone on the nephron?
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1. Increases tubular reabsorption of Na+ by principal cells in cortical collecting ducts
2. Stimulates proton secretion by intercalated cells in the outer medullary sections of the collecting tubule. |
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Does the loss of aldosterone decrease plasma concentration of Na+?
|
No
Loss of sodium will be accompanied by loss of osmotically-obligated water in the urine, so the concentration will not be changed |
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List 4 factors that stimulate aldosterone release.
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1. Decreased ECF volume (low Na+ diet)
2. Increased plasma K+ concentration 3. Increased plasma angiotensin II concentration 4. ACTH |
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What is the most important regulation system for Na+ reabsorption?
What is the rate-limiting step? |
Renin-angiotensin-aldosterone system
Renin release is the rate-limiting step |
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List 3 controls for renin release
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1. Extrarenal baroreceptors (carotid sinus) + intrarenal baroreceptors (afferent arterioles)
2. Macula densa mechanism 3. Sympathetic nerve activity |
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What is the initial stimulus for the renin-angiotensin-aldosterone system?
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Decreased plasma volume
(sensed by carotid sinus and afferent arteriole baroreceptors, and macula densa cells) |
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List 2 ways that angiotensin II decreases sodium excretion.
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1. Decreasing Na+ filtration (decreased GFR)
2. Increasing Na+ reabsorption in proximal and distal nephron |
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Sympathetic nerve activity increases Na+ reabsorption through actions on which parts of the nephron?
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1. Afferent and efferent arterioles
2. Juxtaglomerular cells (secrete renin) 3. Proximal tubule cells |
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Which hormone functions in the "Na+ losing" system?
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Atrial Natriuretic Peptide
|
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Does Norepinephrine participate in the Na+-conserving or Na+-losing system?
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Na+-conserving system
|
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What is the effect of Norepinephrine on GFR and RPF?
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Both are decreased
(due to vasoconstriction) |
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What is the effect of ANP on GFR and RPF?
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Both are increased
(due to vasodilation) |
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Is proximal reabsorption increased or decreased with Norepinephrine?
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INCREASED
(NE stimulates Na+-H+ exchanger, and increases the filtration rate, resulting in a greater peritubular reabsorptive force) |
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What is the effect of Angiotensin on proximal reabsorption?
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Proximal reabsorption is INCREASED
(AGII stimulates Na+-H+ exchanger, and increases the filtration rate, resulting in a greater peritubular reabsorptive force) |
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What is the effect of Aldosterone on distal reabsorption?
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INCREASED reabsorption
|
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What is the effect of ANP on proximal reabsorption?
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DECREASED reabsorption
(due to vasodilation, which leads to less peritubular reabsorptive force-- diluted osmotic gradient) |
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What is the effect of ANP on distal reabsorption?
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DECREASED reabsorption
(inhibits Na+ diffusion in collecting duct) |
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Is medullary blood flow increased or decreased in Na+-conserving systems?
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Decreased
(better gradient, more water reabsorbed) |
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Does ANP increase or decrease medullary blood flow?
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Increase
|
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List 2 ways the water retention occurs.
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1. Disinhibition of left atrial baroreceptors, enhancing ADH release
2. Stimulatory effects of sympathetic activity and angiotensin II on ADH release and thirst |
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For osmoregulation, what is sensed?
What are the sensors and effectors? |
Plasma osmolality is sensed
Sensors: hypothalamic osmoreceptors Effectors: ADH and thirst |
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For volume regulation (sodium balance) what is sensed?
What are the sensors and effectors? |
Effective tissue perfusion is sensed
Sensors: afferent arteriole, atria, carotid sinus Effectors: 1. Renin-angiotensin-aldosterone 2. ADH 3. ANP 4. Norepinephrine |
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What is the effective arterial blood volume (EABV)?
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Portion of the ECF volume in the blood that is "effectively" perfusing the tissues.
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With edema, do both the ECF volume and effective arterial blood volume increase?
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NO.
ECF volume increases, EABV decreases (due to excessive filtration of fluid out of the capillaries into the interstitial fluid) |