Myelin sheath

Definition

The myelin sheath is a protective, insulating layer that surrounds the axons of many neurons, allowing for faster transmission of electrical impulses. This fatty substance is composed primarily of lipids and proteins, which enhance the speed of nerve signal conduction through a process called saltatory conduction. The presence of myelin sheath not only improves communication between neurons but also plays a role in maintaining the overall health and efficiency of neural function.

5 Must Know Facts For Your Next Test

1. Myelin sheaths are formed by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system, highlighting their different roles in myelination.
2. The gaps between segments of myelin are called nodes of Ranvier, where action potentials can jump from one node to another, greatly speeding up signal conduction.
3. The thickness and integrity of the myelin sheath can affect the speed of signal transmission; thicker sheaths allow for faster conduction.
4. Diseases such as multiple sclerosis involve demyelination, leading to severe disruptions in communication within the nervous system and various neurological symptoms.
5. Myelination begins during fetal development and continues into adolescence, demonstrating its importance in the maturation of the nervous system.

Review Questions

• How does the myelin sheath influence the speed of nerve impulse transmission?
  • The myelin sheath significantly influences the speed of nerve impulse transmission by enabling saltatory conduction. In this process, electrical impulses jump between the nodes of Ranvier, which are gaps in the myelin sheath. This jumping mechanism allows impulses to travel much faster than they would along unmyelinated axons, enhancing communication efficiency among neurons.
• What roles do oligodendrocytes and Schwann cells play in the formation of the myelin sheath, and how do they differ?
  • Oligodendrocytes and Schwann cells are both vital for forming myelin sheaths, but they operate in different parts of the nervous system. Oligodendrocytes are responsible for myelinating multiple axons in the central nervous system, while Schwann cells myelinate individual axons in the peripheral nervous system. This distinction is crucial for understanding how different types of nerves are insulated and how that affects their function.
• Evaluate the impact of demyelination on neural communication and provide examples of conditions that result from this process.
  • Demyelination severely disrupts neural communication by slowing down or blocking electrical signal transmission along affected axons. Conditions such as multiple sclerosis exemplify this problem, as damaged myelin sheaths lead to a variety of neurological symptoms like weakness, coordination issues, and sensory disturbances. The loss of myelin not only affects signal speed but can also result in chronic pain and cognitive challenges due to impaired connectivity within neural networks.

Related terms

Axon: A long, slender projection of a neuron that transmits electrical signals away from the cell body to other neurons or muscles.

Oligodendrocytes: Glial cells in the central nervous system that produce the myelin sheath, providing support and insulation to axons.

Demyelination: The process by which the myelin sheath is damaged or destroyed, leading to impaired nerve signal transmission and various neurological disorders.