Biological Systems MCAT Practice Exam

What differentiates white matter from grey matter in the central nervous system?

1. White matter contains unmyelinated axons

2. Grey matter consists of myelinated axons

3. White matter consists of myelinated axons

4. Grey matter does not contain any cell bodies

The correct answer is: White matter consists of myelinated axons

White matter is characterized by its composition of myelinated axons, which are the long, slender projections of neurons that are insulated by a fatty substance called myelin. Myelination increases the speed of electrical impulses along the axon, allowing for more efficient communication between different parts of the nervous system. This structural feature is vital for the rapid relay of signals over long distances, which is critical for coordinating communication across various regions of the central nervous system. In contrast, gray matter primarily consists of neuron cell bodies, dendrites, and unmyelinated axons. The organization of gray matter is essential for processing information, integrating signals, and forming synaptic connections. The presence of myelin is minimal in gray matter, as it is mainly involved with neuronal cell bodies and their synapses. Given this information, the recognition that white matter is primarily made up of myelinated axons aligns with established neuroanatomy and differentiates it effectively from gray matter. This understanding is crucial for comprehending how different parts of the nervous system contribute to overall function and how their structure relates to their roles in neural communication.