57 Neuroglia
Neuroglia of the Central Nervous System
Glia, named from the Greek word for “glue,” support and scaffold neurons while performing other unique functions.
Learning Objectives
Identify the types of neuroglia in central nervous system
Key Takeaways
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 are similar in function to oligodendrocytes and microglial cells.
- Satellite cells perform a similar function to astrocytes,
Key Terms
- 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
Neurogila or glial cells, are non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the central (CNS) and peripheral nervous systems (PNS). It was long believed that neuroglia did not play any role in neuro-transmission, however recent advances have demonstrated that neuroglia play a key role in synapse formation and maintenance.
Neuroglia of the CNS
Neuroglia in the CNS include astrocytes, microglial cells, ependymal cells, and oligodendrocytes. In the human brain, it is estimated that the total number of glia roughly equals the number of neurons, although the proportions vary in different brain areas.
- Astrocytes are delicate, star-shaped branching glial cells. Their numerous radiating processes cling to neurons and their synaptic endings. These astrocytes cover nearly all the capillaries in the CNS. They 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. Astrocytes also regulate the external chemical environment of neurons by removing excess ions and recycling neurotransmitters released during synaptic transmission.
- Microglial cells are small and have thorny processes that can touch the neighboring neurons. Microglial cells can transform into a special type of macrophage that can clear up the neuronal debris. They are also able to monitor the health of neurons by detecting injuries to the neuron.
- Ependymal cells are another glial subtype that line the ventricles of the CNS, forming a permeable barrier between the cerebrospinal fluid (CSF) and underlying cells, and also aid in the circulation of CSF through cilial beat.
- Oligodendrocytes are cells that have fewer processes compared to astrocytes. They line up along the nerve fibers in the CNS and wrap their process tightly around the fibers producing the insulating myelin sheath.
Oligodendrocyte: Oligodendrocytes form the electrical insulation around the axons of CNS nerve cells.
Neuroglia of the PNS
Neuroglia in the PNS include Schwann cells and satellite cells.
- Schwann cells are similar in function to oligodendrocytes and microglial cells, providing myelination to axons in the PNS. They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons.
- Satellite cells are similar in function to astrocytes small cells that surround neurons in sensory, sympathetic, and parasympathetic ganglia, helping to regulate the external chemical environment. They are highly sensitive to injury and inflammation, and appear to contribute to pathological states, such as chronic pain.
Neuroglia: Types of neuroglia found in the CNS and PNS.
Neuroglia of the Peripheral Nervous System
The two kinds of glia cells in the PNS, schwann cells and satellite cells; each have unique functions.
Learning Objectives
Identify the neuroglia of the peripheral nervous system
Key Takeaways
Key Points
- There are two kinds of neuroglia in the peripheral nervous system (PNS): Schwann cells and satellite cells.
- Schwann cells provide myelination to peripheral neurons. Functionally, the schwann cells are similar to oligodendrocytes of the central nervous system (CNS).
- Satellite cells play an important role in modulating the PNS following injury and inflammation. These resemble the astrocytes of the CNS and assist in regulating the external chemical environment.
Key Terms
- glia: Non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the brain and in other parts of the nervous system.
- 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 glial cells: These cells line the exterior surface of neurons in the PNS and neuron cell bodies within ganglia.
The PNS has two kinds of neuroglia: schwann cells and satellite cells. Schwann cells provide myelination to peripheral neurons. They also perform phagocytic functions and clear cellular debris, allowing for the regrowth of PNS neurons. Functionally, the schwann cells are similar to oligodendrocytes of the CNS.
Satellite cells are small glia that surround neurons’ sensory ganglia in the ANS. These resemble the astrocytes of the CNS and assist in regulating the external chemical environment. PNS satellite glia are very sensitive to injury and may exacerbate pathological pain.
Schwann Cell: A Schwann cell in culture
