Biological Systems MCAT Practice Exam

What is the main effect of myelination on neuronal communication?

1. It slows down signal transmission

2. It reduces the number of impulses

3. It increases the speed of conduction

4. It inhibits signal reception

The correct answer is: It increases the speed of conduction

Myelination plays a crucial role in enhancing neuronal communication primarily by increasing the speed of conduction along the axon. Myelin, a fatty substance that wraps around the axons of many neurons, acts as an insulator. This insulation allows electrical impulses, or action potentials, to travel more rapidly. In myelinated axons, the action potentials jump between the nodes of Ranvier—small gaps in the myelin sheath—through a process called saltatory conduction. This method of conduction is much faster compared to continuous conduction in unmyelinated axons, where the action potential must propagate along the entire length of the membrane. The presence of myelin reduces capacitance and increases the resistance of the axonal membrane, which further enhances the speed and efficiency of signal transmission. As a result, myelination is essential for the effective and rapid communication between neurons, which is vital for coordinating complex functions in the nervous system. Understanding this concept demonstrates the importance of myelination in ensuring that signals between neurons are transmitted swiftly and accurately, which is particularly important during activities that require rapid responses.