Mastering A&P Neurophysiology Practice Test

The correct choice indicates that the nodes of a myelinated axon have lower membrane resistance to ion movement compared to the internodes. This characteristic is crucial for the function of myelinated axons, which use saltatory conduction to facilitate faster nerve impulse transmission.

Myelinated axons are surrounded by segments of myelin, which are insulating layers that greatly increase membrane resistance at the internodes. This high resistance minimizes the leak of ions across the membrane, allowing the action potential to maintain its strength as it travels along the axon. When the action potential reaches a node of Ranvier, however, the myelin sheath is absent, leading to a lower membrane resistance in these regions.

At the nodes, voltage-gated sodium channels are densely packed, allowing for the rapid influx of sodium ions when the action potential reaches this point. This influx causes a rapid depolarization that regenerates the action potential, enabling it to "jump" from node to node. This jumping mechanism significantly enhances the speed of the electrical signal while conserving energy.

Thus, the physiological characteristics of the nodes, with their lower membrane resistance to ion movement, are essential for allowing the efficient conduction of nerve impulses along myelinated axons.