Neural Signaling · Paper 1 — Free Biology SL Practice Questions

A researcher stains a section of a peripheral nerve and observes a long axon wrapped in segmented layers of myelin, with regularly spaced unmyelinated gaps between adjacent Schwann cells. Which statement correctly describes the primary function of these gaps?

A researcher examines a cross-section of a peripheral nerve using a transmission electron microscope. Certain axons are surrounded by multiple concentric membrane layers, with periodic gaps where the axon membrane is directly exposed to extracellular fluid. In multiple sclerosis, the immune system degrades these membrane layers along the internodal regions. Which of the following best describes the immediate effect on signal conduction along an affected axon?