Physiology Quiz - Neuronal Action Potential - Part 3
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) This positive feedback cycle is responsible for the spike phase of the action potential.
(2) This (these) agent(s) inhibit(s) voltage-gated Na+ channels of neurons:
(3) At the peak of the neuronal action potential, Vm is approximately +50 mV. Assuming normal intracellular and extracellular K+ concentrations (see here), approximately what is the driving force (in mV) that acts on K+ ions at the peak of the action potential?
(4) Which of the following is NOT consistent with the function of neuronal voltage-gated Na+ channels?
(5) Which of the following is NOT true about the neuronal action potential?