試題詳解

38. Myelin sheaths play a crucial role in accelerating nerve impulse transmission. Which of the following best describes the composition, structure, and mechanism by which myelin sheaths enhance the speed of nerve impulse conduction?
(A) Myelin sheaths are composed of collagen fibers that provide structural support to nerve axons, increasing their diameter and thus conduction speed.
(B) Myelin sheaths are composed of lipids and proteins produced by Schwann cells (in the peripheral nervous system) or oligodendrocytes (in the central nervous system), forming an insulating layer that enables saltatory conduction.
(C) Myelin sheaths are formed by glial cells wrapping around nerve axons, creating an insulating layer that allows for continuous conduction of action potentials.
(D) Myelin sheaths are made of tightly packed microtubules that facilitate the rapid transport of ions along the axon, increasing the speed of action potential propagation.
(E) Myelin sheaths are formed by a network of interconnected gap junctions between adjacent neurons, allowing for direct electrical transmission of signals and bypassing the need for chemical synapses.