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Physiology

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Basic Concepts

Question
67 out of 95
 

True regarding Na/K pump is



A Pumps Na against a gradient

B 5 Na exchanged for 2K

C Increases in intracellular Na

D Hypocalcemia inhibits the pump

Ans. A Pumps Na against a gradient

Na+-K+ ATPase (pump):­

  1. Na+-K+-ATPase catalyzes the hydrolysis of ATP to ADP and uses the energy to extrude three Na+ from the cells and take two K+ into the (ells for each mole of ATP. I.e. the ECF Na+ cone and the K ICF cone or the ICF Na+ cone.
  2. It is an Electrogenic pump, having coupling ratio 3:2 (3Na+: 2K+) Q . Since ECF conc. of Na+ is higher than ICF so it pump Na+ outside call angaist conc. gradient and is similar way, the ICF conc. of K+ is more than ECF, hence pump K+ into the cells agaist the conc. gradient.
  3. Active transport of N a + and K+ is one of major energy using processes in the body on the average it accounts for about 24% of the energy utilized by cells, and in neurons it account for 70%.
  4. In Heart muscle, Na+-K+ ATPase indirectly affect Ca++ transport. Normally one Ca++ goes out side the cells and three Na+ go inside the cells i.e. Antiport. If the Na+-K+ ATPase activity is inhibited by Quabain and related digitalis glycoside

i. intracellular Na+ conc. es the Na+ gradient across the cell membrane decreases Ca++ extrusion decreases

ii. result in intracellular Ca++ conc. →↑contraction of Heart muscle positive inotropic effect.

  1. Regulation of Na+-K+ ATPase activity: ­

Increased activity of pump

Decreased activity of pump

i. Thyroid hormone Q

ii. Aldosterone Q

iii. Insulin Q

iv. G-actin Q

i. Dopamine inhibit the pump phosphorylation in kidney, thus causes natriuresis Q

ii. Ouabain Q

  1. Pump activity is affected by second messengers eg. cAMP and DAG.

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