Cellular Components of the Nervous System: Neuroglia (Glial Cells)

Neuroglia (Glial Cells)

• Support cells that maintain homeostasis, provide structural support, produce myelin, and protect neurons

• Account for 90% of nervous tissue

CNS Neuroglia: Astrocytes

Anchor neurons to capillaries, maintain the blood-brain barrier, and regulate extracellular ion balance

CNS Neuroglia: Oligodendrocytes

Produce myelin for CNS axons, enabling rapid signal conduction

CNS Neuroglia: Microglia

Act as immune cells, removing debris and pathogens

CNS Neuroglia: Ependymal Cells

Line ventricles and circulate cerebrospinal fluid (CSF)

PNS Neuroglia: Schwann Cells

Myelinate axons to increase conduction speed; wraps around axon like a coil

PNS Neuroglia: Satellite Cells

Support and protect neuronal cell bodies in ganglia

Myelin sheath

• Layers of lipid-rich Schwann cells or oligodendrocytes that insulate axons

• Nodes of Ranvier are gaps between myelin segments that facilitate saltatory conduction, speeding up impulses

How is the myelin sheath created?

• Axons are wrapped in myelin, which is like a waxy insulation

• To form the myelin, a Schwann cell (type of neuroglia) wraps itself around the axon, like a coil

• The outer layers of the Schwann cell are called the neurilemma