What are gaps in an axon's myelin sheath called?

The correct answer is that gaps in an axon's myelin sheath are called Nodes of Ranvier. These nodes are critical for the fast propagation of electrical impulses along the axon. The myelin sheath, produced by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system, acts as an insulating layer around the axon, allowing for faster signal transmission.

At the Nodes of Ranvier, the myelin sheath is absent, exposing the axonal membrane. This exposure facilitates the process known as saltatory conduction, where the action potential "jumps" from one node to the next, significantly increasing the speed of signal transmission compared to unmyelinated axons. This structural feature is vital for the efficient functioning of the nervous system, ensuring that signals can travel rapidly over long distances. Understanding this concept is essential for grasping how nervous signals are conducted throughout the body.