33. The critical function of the sodium-potassium pump of neurons is to move (A) Na+ and K+ into the cell and H+ out of the cell through an antiport mechanism. (B)Na+ and K+ out of the cell. (C)Na+ and K+ into the cell. (D)Na+ out of the cell and K+ into the cell. (E) Na+ into the cell and K+ out of the cell.

36. What is the role of calcium in muscle contractions? (A) to break the cross-bridges as a cofactor in the hydrolysis of ATP (B)to spread the action potential through the T-tubules (C)to transmit the action potential across the neuromuscular junction (D)to bind with troponin, changing its shape so that binding sites on the actin filament are exposed (E) to re-establish the polarization of the plasma's membrane following an action potential

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