Myelin sheath

Definition

The myelin sheath is a protective covering that surrounds axons in the nervous system. It helps increase the speed at which electrical impulses travel along the nerve cells.

5 Must Know Facts For Your Next Test

1. Myelin sheaths are primarily composed of lipids and proteins.
2. They are produced by Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system.
3. The gaps between segments of myelin sheath are called Nodes of Ranvier, which facilitate rapid signal transmission.
4. Myelination is crucial for proper functioning of the nervous system; damage to myelin can lead to neurological diseases such as multiple sclerosis.
5. Myelinated axons conduct electrical impulses faster than unmyelinated axons due to saltatory conduction.

Review Questions

• What are the primary components of the myelin sheath?
• Which cells produce myelin sheaths in the central and peripheral nervous systems?
• How do Nodes of Ranvier contribute to nerve impulse transmission?

Related terms

Axon: The long, threadlike part of a nerve cell along which impulses are conducted from the cell body to other cells.

Schwann Cells: Glial cells in the peripheral nervous system that produce myelin sheaths around neuronal axons.

Saltatory Conduction: The process by which electrical impulses jump from one Node of Ranvier to another, speeding up signal transmission.