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13 Cards in this Set
- Front
- Back
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Determination of ECFV |
[Na] is constant -> ECFV determined by the amount of EC Na ISF ~ PV [eq. by Starling forces] |
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Long-term control of BP |
~ control of BV, by kidneys: - PV (Δ in ECFV) - RBC volume (via erythropoietin) - Na appetite |
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Receptors governing Na balance |
High-P R's - dominant => RAAS, sNS - afferent arterioles (kidney) [carotid sinus, aortic arch - minor role: adaptable -> short-term] - renin-producing granular cells lack contractile fibers -> chronic Low-P R's => ANP - cardiac atria, VC, large pulmonary vessels - distensible -> greatest response to ΔBP -> intermediate ctrl [adaptible; water immersion scenario] |
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RAAS (Renin-Angiotensin-Aldosterone System) |
Granular cells (afferent arterioles): low BP/[Na] => -> Renin: (Antensinogen -> AI) -> ACE: (AI -> AII) [surface of endothelial cells] => AII |
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Angiotensin II - renal effects |
- ↑ Na reabsorption in PT (Na/H exchanger) - lowers set pt -> ↑ sensitivity of TGF: ↑ NaCl in macula densa -> ↓↓↓ GFR- ↓ eff. arterioles -> vasa recta reabsorption from PT - ↓ medullary BF -> ↑ urinary concentrating ability & ↑ Na reabsorption in TAL |
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Angiotensin II - extrarenal effects |
- ↑ aldosterone secretion in zona glomerulosa, adrenal cortex - direct vasoconstriction; indirect: -- sNS -> Sm -- ↓ vagal tone & baroreflex sensitivity -- ↑ norepinephrine release & ↓ reuptake in synapses - ↑ thirst & Na appetite |
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Activity of Aldosterone |
-> Mineralocorticoid R (MR) - intracellular TF Most important for maintaining Na homeostasis: - ↑ Na reabsorption in DT & CD (reg. final Na excretion) - ↑ Na absorption in colon & sweat glands -> ↓ extrarenal Na loss - ↑ Na intake: CNS => salt appetite; ↑ taste bud sensitivity to NaCl; ↓ salivary [Na] -> in general: ↑ ENaC (CD, epithelia) & Na/K-ATPase |
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Low Na delivery -> CD ensured by |
TGF (tubulo-glomerular fb) AII & catecholamines -> PT na reabsorption aldosterone -> DT |
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Regulation of RAA axis |
Renin release from granular cells in afferent aa's = rate-limiting step
- ↓ BP -> ↑ renin (X ↑ renal perfusion) - sNS -> afferent aa.'s -> ↑ renin - macula densa: ↓ NaCl -> ↑ renin - pressor hormones (AII) -> -fb -> ↓ renin - prostaglandins, NO, ANP -> ↓ renin Aldosterone synthesis: AII ↑, ANP & plasma [K] ↓ |
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Renal effects of sympathetic NS (sNS) |
-> afferent aa.'s -> ↑ renin -> PT -> Na reabsorption |
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Activity of Atrial Natriuretic Peptide (ANP) |
Distension of atria -> ANP (also BNP released by ventricles) -> ↓ heart contractility -> vasodilators (resistance vv.'s, venules, large v.'s) [↓ preload & afterload] -> ↑ capillary permeability -> ↑ Na excretion: - ↑ GFR & ↑ medullary BF - ↓ Na reabsorption (medullary CD's) - ↓ renin, aldosterone, ADH |
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Pressure natriuresis |
↑ in P(perfusion) -> ↓ Na reabsorption -> ↑ Na excretion (while GFR is constant) |
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Renal regulation of RBC V |
renal O2 consumed by Na reabsorption: ↑ RBF -> ↑ GFR -> ↑ Na reabsorption => Na balance maintained =>> p(O2) stable over a wide range of RBF, p(O2, aff.) - p(O2, eff.) ~ constant -> ideal for monitoring Δp(O2): Δ p(O2) ~ ? RBC V (info integration) -> Δ? Epo (erythropoietin) in interstitial fibroblasts (b/w PT's) |
