Neural transmission in the nodes of Ranvier

The nodes of Ranvier increase the efficiency of neural transmission by means of which of the following?

• a.Decelerating the closing of Na -gated channels
• b.Enhancing myelination of the internodal segment
• c.Sequestration of Na entry into the axon
• d.Multiple firings due to local ionic currents around the node
• e.Decreasing threshold for the action potential

 The answer is  (c ).

The nodes of Ranvier increase the efficiency of nodal conduction because of restriction (sequestration) of energy–dependent Na influx to the node. The nodes of Ranvier represent
the space between adjacent units of myelination.
This area is bare in the CNS, whereas in the PNS the axons in the nodes are partially covered by the cytoplasmic tongues of adjacent Schwann cells. Most of the Na -gated channels are located in the bare areas. Therefore, spread of depolarization from the nodal region along the axon occurs until it reaches the next node.
This is often described as a series of jumps from node to node, or saltatory conduction.