MUSCLE PHYSIOLOGY

Detailed explanation-1: -The subsequent return to resting potential, repolarization, is mediated by the opening of potassium ion channels. To reestablish the appropriate balance of ions, an ATP-driven pump (Na/K-ATPase) induces movement of sodium ions out of the cell and potassium ions into the cell.

Detailed explanation-2: -At the peak action potential, K+ channels open and K+ begins to leave the cell. At the same time, Na+ channels close. The membrane becomes hyperpolarized as K+ ions continue to leave the cell. The hyperpolarized membrane is in a refractory period and cannot fire.

Detailed explanation-3: -They use energy supplied by the cell to actually pump ions in or out of the cell, by force if you will. The best examples are the sodium-potassium pumps on the neuron’s membranes. These pumps push sodium ions out of the cell, and potassium ions (K+) into the cell.

Detailed explanation-4: -Na+ is critical for the action potential in nerve cells. As shown in Figure 2.1, action potentials are repeatedly initiated as the extracellular concentration of Na+ is modified. As the concentration of sodium in the extracellular solution is reduced, the action potentials become smaller.