Describe the saltatory conduction of nerve impulses.
Saltatory conduction of nerve impulses: When an impulse travels along a myelinated neuron, depolarization occurs only at the nodes of Ranvier where the insulating myelin sheath is absent and the voltage-gated ion channels are concentrated. Because the action potential jumps from node to node, transmission of impulse is more rapid in myelinated neuron. This is called the saltatory conduction of nerve impulse. Saltatory conduction is responsible for the greater speed of an impulse travelling along a myelinated neuron than along a non-myelinated one. Myelinated neurons require less energy for action because only the nodes are depolarised and few ions are required to jump back into position by the ion pumps. An impulse conducted in this fashion moves very rapidly, upto 120 metres per second for large diameter In non-myelinated nerve fibres, the ionic flow and depolarisation are repeated along the entire length of the fibre. Therefore, impulse conduction is slow in such nerve fibre.
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