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.
Test your basic knowledge of the neuronal action potential by taking this simple quiz below. For more information about the neuronal action potential, see the Neuronal Action Potential lecture notes.
(1) A typical neuron has a resting membrane potential of about:
(2) The following ion(s) is/are involved in the neuronal action potential:
(3) At the peak of the action potential, the membrane potential is:
(4) At what membrane voltage do neuronal voltage-gated Na+ channels become activated?
(5) At what membrane voltage do neuronal voltage-gated K+ channels become activated?
(6) The spike phase of the neuronal action potential is due to:
(7) The hyperpolarization phase of the action potential is due to:
(8) Upon opening, voltage-gated K+ channels of neurons enter an inactivate state in a manner similar to voltage-gated Na+ channels of neurons.
(9) During this phase of the action potential, if a second stimulus is applied to the neuron (no matter how strong the stimulus), a second action potential will not be generated.
(10) In the nervous system, the strength of the stimulus is coded into:
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Posted: Friday, August 8, 2014 Last updated: Friday, August 8, 2014