Table of Contents
What cells wrap their cytoplasmic extensions around thick neuron fibers in the CNS?
Oligodendrocytes are specialized glial cells that wrap themselves around neurons present in the CNS. Oligodendrocytes are primarily responsible for maintenance and generation of the myelin sheath that surrounds axons. They also participate in axonal regulation and the sculpting of higher order neuronal circuits [51].
What type of support cell wraps nerves in the CNS in a myelin sheath?
In the central nervous system (CNS) — the brain and spinal cord — cells called oligodendrocytes wrap their branch-like extensions around axons to create a myelin sheath.
What do Schwann cells do?
Schwann cells (SCs) are the major glial cell type in the peripheral nervous system. They play essential roles in the development, maintenance, function, and regeneration of peripheral nerves.
What is the role of the oligodendrocytes?
In the central nervous system (CNS), oligodendrocytes assemble myelin, a multilayered sheath of membrane, spirally wrapped around axonal segments and best known for its role in enabling fast saltatory impulse propagation1,2.
How do Schwann cells form myelin sheath?
Myelin is formed by Schwann cells in the peripheral nervous system (PNS) and oligodendrocytes in the central nervous system (CNS). Each Schwann cell forms a single myelin sheath around an axon. Myelin itself forms by the spiral wrapping around an axon of an enormously expanded glial plasma membrane that then compacts.
Are Schwann cells in the CNS?
Schwann cells are excluded from the CNS during development by the glial limiting membrane, an area of astrocytic specialisation present at the nerve root transitional zone, and at blood vessels in the neuropil. Extensive Schwann cell CNS myelination may have therapeutic significance in human myelin disease.
Do CNS neurons have Schwann cells?
Schwann cell, also called neurilemma cell, any of the cells in the peripheral nervous system that produce the myelin sheath around neuronal axons. These cells are equivalent to a type of neuroglia called oligodendrocytes, which occur in the central nervous system.
Do oligodendrocytes wrap around axons?
Oligodendrocytes form the electrical insulation around the axons of CNS nerve cells. A single oligodendrocyte can extend its processes to 50 axons, wrapping approximately 1 μm of myelin sheath around each axon; Schwann cells, on the other hand, can wrap around only one axon.
Which two glial cells wrap around and insulate axons?
Figure 16.7. Glial cells support neurons and maintain their environment. Glial cells of the (a) central nervous system include oligodendrocytes, astrocytes, ependymal cells, and microglial cells. Oligodendrocytes form the myelin sheath around axons.
How are Schwann cells used in the central nervous system?
Schwann cells, in the peripheral nervous system, and oligodendrocytes, in the central nervous system, wrap around the axons of neurons to form myelin sheaths. Myelin sheaths are electrical insulators and prevent current from leaving axons.
When does the Schwann cell wrap the axon?
During this repeated wrapping, more and more cytoplasm is pushed to the periphery of the Schwann cell. When the myelinatiion process is complete, the Schwann cell covers the axon with many layers of plasma membranes, consisting mostly of lipids.
How big is the myelin sheath in a Schwann cell?
This covering is called a myelin sheath, and the axon is said to be myelinated. The Schwann cell cytoplasm outside the myelin sheath contains the cell nucleus and is referred to as the neurilemma. Schwann cells are only 0.3 mm to 1.5 mm in length, thus many are required to myelinate the length of a single axon.
What makes up the lamina of a Schwann cell?
Both myelinating and non-myelinating Schwann cells are covered by a basal lamina. The outside of the lamina is surrounded by a layer of connective tissue namely the endoneurium, which contains blood vessels, fibroblasts, and macrophages.