What purpose does the myelin sheath serve?

The myelin sheath plays a crucial role in the functioning of the nervous system by significantly enhancing the conduction speed of impulses along nerve fibers. This specialized structure is a fatty layer that surrounds the axons of many neurons. By insulating the axon, the myelin sheath allows electrical impulses, known as action potentials, to travel more quickly and efficiently. This rapid transmission is due to a process called saltatory conduction, where the impulse jumps from one node of Ranvier (gaps in the myelin sheath) to the next, rather than traveling along the entire length of the axon.

This increased speed of conduction is vital for the effective communication between neurons, enabling swift reflexes and coordination of bodily functions. In contrast, the other options refer to processes not directly associated with the primary function of the myelin sheath. While protecting nerve endings and transmitting signals are important aspects of neuronal function, they are not the specific roles played by myelin. Similarly, the secretion of neurotransmitters is a function of neurons, specifically at synapses, and is not related to the myelin sheath's responsibilities. Thus, the primary purpose of the myelin sheath is indeed to enhance the conduction speed of impulses.