In myelinated axons, where do action potentials primarily occur?

In myelinated axons, where do action potentials primarily occur?

• A. Nodes of Ranvier
• B. Soma
• C. Dendrites
• D. Axon hillock

Answer: (A)

In myelinated axons, action potentials are regenerated at the nodes of Ranvier. The myelin sheath wraps the internodes, raising membrane resistance and lowering capacitance, which prevents depolarization from triggering new spikes along those insulated stretches. At each node, there’s a high density of voltage-gated Na+ channels, so when depolarization reaches the node, it crosses threshold and fires an action potential. This creates saltatory conduction, with the signal jumping from node to node and speeding up transmission. The axon hillock is a common initiation site in many neurons, but along a myelinated axon the essential regenerative events powering propagation occur at the nodes of Ranvier.

In myelinated axons, action potentials are regenerated at the nodes of Ranvier. The myelin sheath wraps the internodes, raising membrane resistance and lowering capacitance, which prevents depolarization from triggering new spikes along those insulated stretches. At each node, there’s a high density of voltage-gated Na+ channels, so when depolarization reaches the node, it crosses threshold and fires an action potential. This creates saltatory conduction, with the signal jumping from node to node and speeding up transmission. The axon hillock is a common initiation site in many neurons, but along a myelinated axon the essential regenerative events powering propagation occur at the nodes of Ranvier.