- The myelin sheath is a lipid-rich layer that surrounds the axons of many neurons, particularly in the peripheral nervous system.
- Its primary function is to increase the velocity of nerve impulse transmission.
- This is accomplished through a mechanism known as saltatory conduction, where the action potentials "jump" from one Node of Ranvier (gaps in the myelin sheath) to another, significantly speeding up the propagation of electrical signals along the nerve fiber.

- While the myelin sheath does provide some protection and metabolic support through the associated Schwann cells, these roles are secondary compared to its primary role of enhancing conduction speed.
- It is not directly involved in synaptic neurotransmitter release, which occurs at the axon terminal and is managed by specialized cellular machinery unrelated to myelin.

Key points:
- The myelin sheath is essential for rapid nerve impulse conduction.
- It achieves this by enabling saltatory conduction.
- This structural adaptation dramatically increases signal transmission velocity.
- Other functions like protection and metabolic support are less central.

Reference: Kandel, E.R., Schwartz, J.H., Jessell, T.M. Principles of Neural Science, 5th Edition, Chapter 8: The Axon and Myelin