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Physiology Quiz -
Neuronal Action Potential - Part 4
Excitable cells of the nervous system (i.e., neurons) generate nervous impulses. Nervous impulses are the electrical signals by which neurons talk to one another and also to other cells of the body. The nervous impulse is referred to as the action potential. An action potential is a brief (only a few milliseconds) reversal of the membrane potential (Vm). At rest, the Vm of a neuron is around −70 mV (closer to the equilibrium potential for potassium, VK), but during an action potential, Vm transiently approaches +50 mV (closer to the equilibrium potential for sodium, VNa). The membrane potential then rapidly returns to the resting potential and even briefly goes beyond the resting potential to approach VK before finally returning to the resting value of about −70 mV. The entire process takes about 3-5 ms. This potential reversal of more than 100 mV is responsible for electrical signaling in the nervous system, and is the basis of information transmission in the nervous system.
(1)   In action potentials, the threshold potential refers to the voltage at which:
(2)   In action potentials, overshoot refers to the:
(3)   At the peak of the action potential, plasma membrane permeability to K+ (pK) is higher than the permeability to Na+ (pNa).
(4)   At the peak of the action potential, plasma membrane permeability to Na+ (pNa) is higher than the permeability to K+ (pK).
(5)   Graded potentials are all-or-nothing.
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Posted: Tuesday, September 29, 2015