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19 Cards in this Set
- Front
- Back
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What is secreted by tubules? |
H+, K+, organic anions/cations |
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What is K+ secretion controlled by? |
Aldosterone
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Where does secretion of K+ occur? |
In distal tubule and collecting ducts
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What happens to K+ secretion when K+ depleted? |
Reduced - only small % of filtered K+ that escapes re-absorption in proximal tubule is excreted
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Does secretion or absorption of K control level? |
Secretion
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How is K+ secreted? |
Na-K pump
Na in/ K out of lateral space from principle cell Passive diffusion of K into tubule lumen through leaky channels Basolateral pump - K secreted from peritubular capillary |
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What happens in proximal tubule? |
No leaky channels - no K secretion
Basolateral membrane - K pumped into cell moves back to interstitial fluid So maintains Na reabsorption, no net on K |
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How is K secretion controlled? |
Aldosterone increases K secretion/Na reabsorption Rise in plasma K, stimulates adrenal cortex. Fall in plasma Na - stimulates RAAS |
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What can lead to K deficiency? |
Fall in Na, ECF volume, arterial pressure
Increases Renin Increases Angiotensin I and II Increases Aldosterone Increases Tubular secretion and excretion of K |
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What are the functions of organic ion secretory system? |
- Add particular organic ion to filtered
- Organic ions reversibly bond to plasma proteins - Proximal tubule secretory system eliminates foreign compounds |
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In the proximal tubule, what is reabsorbed? |
67% of filtered Na actively All glucose, aa. secondary active transport 65% filtered water, osmotically 50% filtered urea Almost all K - no control |
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In the proximal tubule, what is secreted? |
Variable H+ Organic ion secretion |
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In the distal tubule, what is reabsorbed? |
Variable Na - aldosterone controlled Variable water - vasopressin controlled |
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In the distal tubule, what is secreted? |
H+ - variable Organic ion |
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How is urea reabsorbed? |
Passively When Na+ is reabsorbed, water osmotically follows creating conc. gradient for urea. Urea moves through cells or by paracellular transport |
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How are plasma proteins reabsorbed? |
Receptor-mediated endocytosis
Once in cells, proteins are digested in lysosomes and released as aas. |
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What is excretion of glucose called? |
Glucosuria
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What are substances brought into the body called? |
Xenobiotics
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Secretion: How do organic ions enter lumen by facilitated diffusion |
- Direct active transport - Na/K-ATPase keeps intracellular Na low - Secondary AT - Na-dicarboxylate cotransporter concentrates a dicarboxylate inside cell using energy stored in Na conc grad - Tertiary indirect AT - basolateral OAT concentrates organic anions inside cell, using energy from dicarboxylate grad. - Organic anions enter lumen by fac. diffusion. |
