Myelinated neurons

Definition

Myelinated neurons are nerve cells that have a protective insulating layer called myelin wrapped around their axons, which enhances the speed and efficiency of electrical signal transmission. The presence of myelin allows action potentials to jump between the nodes of Ranvier, leading to faster impulse conduction compared to unmyelinated neurons. This adaptation is crucial for the rapid communication necessary in complex nervous systems.

5 Must Know Facts For Your Next Test

1. Myelinated neurons can transmit signals at speeds up to 120 meters per second, significantly faster than unmyelinated neurons.
2. Myelination occurs during development and is essential for proper nervous system function; demyelination can lead to disorders such as multiple sclerosis.
3. The myelin sheath is formed by specialized glial cells: oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system.
4. Myelination not only speeds up signal transmission but also conserves energy for neurons by reducing the number of ion exchanges needed during action potential propagation.
5. In vertebrates, myelination is a key feature that supports complex behaviors and rapid responses, allowing for efficient communication between different parts of the nervous system.

Review Questions

• How does myelination influence the speed of nerve impulse transmission in myelinated neurons?
  • Myelination significantly increases the speed of nerve impulse transmission due to the insulating properties of the myelin sheath. In myelinated neurons, action potentials jump between the nodes of Ranvier, a process known as saltatory conduction. This method allows signals to travel much faster compared to unmyelinated neurons, where the impulses must travel continuously along the entire length of the axon.
• Discuss the role of glial cells in the formation and maintenance of the myelin sheath in myelinated neurons.
  • Glial cells play a crucial role in both the formation and maintenance of the myelin sheath surrounding myelinated neurons. In the central nervous system, oligodendrocytes extend their membranes to wrap around multiple axons, creating segments of myelin. In contrast, Schwann cells perform this function in the peripheral nervous system by wrapping around individual axons. These glial cells not only provide insulation but also support neuronal health and facilitate regeneration after injury.
• Evaluate the impact of demyelination on neural function and its associated neurological disorders.
  • Demyelination has a profound impact on neural function as it disrupts the normal flow of electrical signals along myelinated neurons. This can lead to slow or blocked nerve impulses, resulting in symptoms such as muscle weakness, impaired coordination, and cognitive difficulties. Neurological disorders like multiple sclerosis arise from autoimmune attacks on myelin, highlighting how critical this insulating layer is for maintaining effective communication within the nervous system and overall health.

Related terms

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

Myelin sheath: The fatty insulating layer that surrounds the axons of myelinated neurons, composed primarily of lipids and proteins.

Nodes of Ranvier: The small gaps in the myelin sheath where ion channels are concentrated, allowing for the rapid propagation of action potentials along the axon.