Study Guide: Lecture 31 - Transport & Excretion
7 Cards in this Set
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Reabsorption of Na, Glucose, HCO2, etc.
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Na/K pump reabsorbs Na> Na flows in via Na/Pi symport, Na/H antiport, Na/Glu,AA symport> Glu,AA reabsorb through channels> H in lumen makes CO2+H20> CO2 reabsorbed into cell> make HCO3- in cell> reabsorbed w/ 1Na/3HCO3- symport
↑[ions] in ECF cause water to follow, ↑[Cl] in lumen flows t…
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Secretion of H ions - prevent acidification
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HCO3-/Cl- transporter, H2O dissociates into H and OH, H pumps pumps H out into distal tubule & collecting duct, also H/K pump
Mechanisms will stop is gradient is too steep, they must be buffered to not make the pH too low
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Fate of secreted H ions: H buffering in urine
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Bicarbonate: H+HCO3→ H2CO3→ CO2 (re-enters cell to make more HCO3)+H20
Diabastic phosphate → monobastic phosphate: H+NaNaHPO4→ NaH2PO4 + Na (reabsorbed)
Ammonia→ammonium: H+NH3 (very toxic, diffuses everywhere)→ NH4 (trapped, cannot diffuse). In distal tubule & collecting duct, causes N…
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K Homeostasis (most abundant ion in body)
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excretion rate = intake rate constantly
Proximal tubule: most filtered K is reabsorbed
Distal Tubule: regulated K secretion (PRINCIPAL CELLS) or reabsorption (INTERCALATED CELLS)
Rate of K secretion ∝ flow in area (if dehydrated, K does not get secreted ∴ hyperkalemia)
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Secretion of K Ions & Xenobiotics
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Na/K pump, ROMK (renal outer medulla K channel I, inwardly rectifying K to lumen)
OAT (organic Anion transporters)
OCT (organic cation transporters)
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Excretion & Clearance
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Excretion Rate = Filtration + Secretion - Reabsorption
INULIN: not secreted or reabsorbed, so
Excretion rate = filtration rate
V = volume of urine formed, U = concentration in urine
Rate of Excretion = VxU (mg/min)
Rate of Filtration = GFR x [Inulin]plasma
GFR = VxU/[inulin]plasma
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Micturition/Urination
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1. Stretch receptors activated by full bladder
2. Parasymp stimulation of muscle contraction, inhibition of MNs to external sphincter muscle
3. Contractions increase P, force internal sphincter open, urination
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Study Guide: Lecture 31 - Transport & Excretion