Biological Systems MCAT Practice Exam 2025 – Complete Study Resource

The connections between afferent and efferent neurons are primarily mediated by interneurons. Interneurons function as connectors or relay neurons within the central nervous system (CNS). They play a crucial role in processing information by relaying signals between sensory neurons (afferent neurons) that carry information from sensory receptors to the CNS, and motor neurons (efferent neurons) that convey commands from the CNS to effectors like muscles or glands.

Interneurons are essential for integrating sensory input and directing appropriate motor responses, often facilitating complex reflex arcs and pathways involved in higher-order functions such as learning and decision-making. They form networks that enable communication within the CNS, thus allowing for the processing of information that guides both voluntary and involuntary actions.

The other options, while involving different types of neurons or support cells, do not serve the primary role of directly connecting afferent and efferent pathways to mediate these neuronal communications as effectively as interneurons do.