FRANCIS LEROY, BIOCOSMOS / SCIENCE PHOTO LIBRARY FRANCIS LEROY, BIOCOSMOS / SCIENCE PHOTO LIBRARY
Nerve impulse propagation. Artwork showing the mechanism of propagation of the action potential (spike in voltage) which is known as a nerve impulse. The sequence runs from top to bottom, with the nerve impulse (red) moving from left to right along the nerve (blue). The cellular mechanism involves voltage-gated ion channels in the nerve cell membrane (grey). Depending on the nerve, either sodium or calcium ions flow into the nerve during the propagation of the nerve impulse, and potassium ions are actively transported out to return the voltage to the resting potential and end the impulse. Both these mechanisms are shown by the arrows.
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