![]() ![]() ![]() When the action potential occurs in the first segment of the axon, it quickly creates a similar change in the next segment, which then stimulates the next segment, and so forth as the positive electrical impulse continues all the way down to the end of the axon. The electrical charge moves down the axon from segment to segment, in a set of small jumps, moving from node to node. Once the action potential occurs, the number of positive ions exceeds the number of negative ions in this segment, and the segment temporarily becomes positively charged.Īs you can see in Figure 3.4 “The Myelin Sheath and the Nodes of Ranvier”, the axon is segmented by a series of breaks between the sausage-like segments of the myelin sheath. This change in electrical charge that occurs in a neuron when a nerve impulse is transmitted is known as the action potential. When the segment of the axon that is closest to the cell body is stimulated by an electrical signal from the dendrites, and if this electrical signal is strong enough that it passes a certain level or threshold, the cell membrane in this first segment opens its gates, allowing positively charged sodium ions that were previously kept out to enter. Normally, the axon remains in the resting potential, a state in which the interior of the neuron contains a greater number of negatively charged ions than does the area outside the cell. The electrical signal moves through the neuron as a result of changes in the electrical charge of the axon. This video clip shows a model of the electrochemical action of the neuron and neurotransmitters. Video Clip: The Electrochemical Action of the Neuron
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