What is the myelin sheath in relation to neurons?

The myelin sheath is an insulating layer that surrounds the axons of some neurons, and it is primarily formed by the cell membrane of Schwann cells in the peripheral nervous system. This insulation is crucial for the efficient conduction of electrical impulses along the nerve fibers. Myelin increases the speed at which signals can travel down the axon by allowing the impulses to jump between the nodes of Ranvier, which are small gaps in the myelin sheath. This process significantly enhances the speed of neural communication, making the signaling more rapid and efficient.

The other options describe different aspects of neuron anatomy and function but do not accurately define the myelin sheath. A protective bulb at the end of the axon refers to the terminal where neurotransmitters are released, rather than the sheath itself. The component responsible for neurotransmitter release relates to synaptic function. Lastly, a structure connecting sensory and motor neurons pertains to the role of interneurons or reflex arcs, which is distinct from the function of the myelin sheath.