Myelin sheath

Definition

The myelin sheath is a protective layer of fatty material that surrounds the axons of neurons, enhancing the speed and efficiency of electrical signal transmission. This sheath is crucial for the proper functioning of the nervous system, as it allows for quicker communication between nerve cells by insulating axons and facilitating saltatory conduction, where action potentials jump between nodes of Ranvier.

5 Must Know Facts For Your Next Test

1. The myelin sheath is primarily composed of lipids, which provide electrical insulation to the axon, preventing loss of signal during transmission.
2. In the peripheral nervous system, Schwann cells are responsible for forming the myelin sheath around individual axons.
3. Demyelination, or the loss of the myelin sheath, can lead to neurological disorders such as multiple sclerosis, where signal transmission is impaired.
4. The presence of myelin greatly increases the conduction velocity of action potentials, making it essential for rapid reflexes and coordinated movements.
5. Myelination occurs at different stages during development, with most neurons becoming fully myelinated by late adolescence.

Review Questions

• How does the structure of the myelin sheath contribute to its function in neuron signal transmission?
  • The myelin sheath is structured as a series of tightly wrapped layers around the axon, formed by glial cells. This structure provides insulation, which prevents electrical signal loss and allows for faster transmission. The insulation enables saltatory conduction, where action potentials jump between nodes of Ranvier, significantly speeding up the communication between neurons compared to unmyelinated fibers.
• What roles do oligodendrocytes and Schwann cells play in the formation of the myelin sheath within different parts of the nervous system?
  • Oligodendrocytes are responsible for creating the myelin sheath around multiple axons in the central nervous system, while Schwann cells form myelin around individual axons in the peripheral nervous system. Both cell types are essential for maintaining proper nerve function and ensuring that electrical impulses travel efficiently across neurons. The differences in how these cells contribute to myelination are crucial for understanding how various neurological diseases affect different parts of the nervous system.
• Evaluate how demyelination affects neurological function and what implications this has for understanding diseases such as multiple sclerosis.
  • Demyelination disrupts the insulating properties of the myelin sheath, leading to slower or blocked nerve signal transmission. In diseases like multiple sclerosis, this loss affects motor control, sensation, and cognitive functions. Understanding demyelination helps researchers develop treatments aimed at repairing or protecting myelin, which could potentially restore lost functions and improve quality of life for individuals affected by these neurological disorders.

Related terms

Axon: A long, slender projection of a neuron that conducts electrical impulses away from the neuron's cell body.

Oligodendrocytes:

Glial cells in the central nervous system responsible for forming the myelin sheath around axons.

Nodes of Ranvier: Gaps in the myelin sheath along an axon that facilitate rapid conduction of nerve impulses through saltatory conduction.