Anatomy Practice Exam

What is the purpose of the myelin sheath?

1. To facilitate gas exchange with blood

2. To suppress nerve signal transmission

3. To insulate nerve fibers and speed up conduction

4. To store energy for neural function

The correct answer is: To insulate nerve fibers and speed up conduction

The myelin sheath serves a critical purpose in the nervous system by insulating nerve fibers and significantly increasing the speed of electrical signal transmission along these fibers. Myelin is a fatty substance produced by specialized cells (oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system) that wraps around the axons of neurons. This insulation is vital because it reduces the loss of electrical signals as they travel along the axon, thus allowing for efficient and rapid communication between neurons. The presence of myelin facilitates a process known as saltatory conduction, where the action potential jumps between the nodes of Ranvier (gaps in the myelin sheath). This not only speeds up the conduction velocity but also conserves energy for the neuron since fewer ions need to be pumped across the membrane during signal transmission. Understanding the role of the myelin sheath highlights the importance of this structure in maintaining efficient neural function and effective communication within the nervous system.