MCAT Content / Nerve Cell / Glial Cells Neuroglia

Glial cells, neuroglia

Topic: Nerve Cell

Neuroglia or glial cells maintain homeostasis, form myelin, and provide support and protection for neurons in the CNS and PNS.

Glial cells guide developing neurons to their destinations, buffer ions and chemicals that would otherwise harm neurons and provide myelin sheaths around axons. In recent advances, neuroglia plays a key role in synapse formation and maintenance.

In the CNS there are 4 types of glial cells. Astrocytes make contact with both capillaries and neurons in the CNS to provide nutrients and other substances to neurons. Microglial cells monitor and maintain the health of neurons by detecting injuries to the neuron. Ependymal cells involved in the production of cerebrospinal fluid, which serves as a cushion for the brain. Oligodendrocytes line up along the nerve fibers in the CNS and wrap their process tightly around the fibers producing the insulating myelin sheath.

Neuroglia in the PNS includes Schwann cells and satellite cells. Schwann cells are similar in function to oligodendrocytes and microglial cells, providing myelination to axons in the PNS. Satellite cells are highly sensitive to injury and inflammation and appear to contribute to pathological states, such as chronic pain.

 


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Key Points

• Neuroglia in the CNS include astrocytes, microglial cells, ependymal cells, and oligodendrocytes.

• Neuroglia in the PNS include Schwann cells and satellite cells.

• Astrocytes support and brace the neurons and anchor them to their nutrient supply lines. They also play an important role in making exchanges between capillaries and neurons.

• Microglial cells can transform into a special type of macrophage that can clear up the neuronal debris while monitoring the health of the neuron.

• Ependymal cells are another glial subtype that line the ventricles of the CNS to help circulate the CSF.

• Oligodendrocytes are cells that wrap their process tightly around the fibers producing an insulating covering called myelin sheath.

• Schwann cells provide myelination to peripheral neurons. Functionally, the Schwann cells are similar to oligodendrocytes of the central nervous system (CNS); they are similar in function to oligodendrocytes and microglial cells.

• Satellite cells perform a similar function to astrocytes; they play an important role in modulating the PNS following injury and inflammation.


Key Terms

Neuron: An electrically excitable cell that communicates with other cells via specialized connections called synapses. It is the main component of nervous tissue in all animals except sponges and placozoa.

Myelin: A white, fatty material, composed of lipids and lipoproteins, that surrounds the axons of nerves.

Glia: Non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the brain, and for neurons in other parts of the nervous system such as in the autonomic nervous system.

Astrocyte: a neuroglial cell, in the shape of a star, in the brain

Schwann cells: The principal glia of the PNS, these cells are involved in the conduction of nervous impulses along axons, nerve development and regeneration, trophic support for neurons, production of the nerve extracellular matrix, modulation of neuromuscular synaptic activity, and presentation of antigens to T-lymphocytes.

Satellite cells: These cells line the exterior surface of neurons in the PNS and neuron cell bodies within ganglia.

CNS: central nervous system consists of the brain and spinal cord

Homeostasis: the state of steady internal, physical, and chemical conditions maintained by living systems

Axon: long slender projection of a nerve cell that conducts nerve impulses away from the cell body to other neurons, muscles, and organs

PNS: peripheral nervous system consists of all of the nerves that lie outside the brain and spinal cord

Microglial cells: monitor and maintain the health of neurons

Ependymal: produce cerebrospinal fluid

Oligodendrocytes line up along the nerve fibers in the CNS and wrap their process tightly around the fibers producing the insulating myelin sheath.



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