4. Neuroglia and Myelin

Neuroglia?

Glial cells that support, insulate, and protect neurons

Four CNS neuroglia?

Astrocytes

oligodendrocytes

microglial cells

ependymal cells

Two PNS neuroglia?

Neurolemmocytes (Schwann cells)

satellite cells

Astrocytes?

Star-shaped

anchor neurons and vessels, regulate brain environment

help form blood-brain barrier, repair tissue

Oligodendrocytes?

Wrap CNS axons to form myelin

Microglial cells?

Wandering phagocytes

ingest microbes, dead neurons, debris

Ependymal cells?

Ciliated

line CNS cavities

make and circulate CSF

Neurolemmocytes (Schwann cells)?

Wrap PNS axons to form myelin

Satellite cells?

Surround PNS cell bodies; supportive

Myelin sheath?

Repeating layers of plasma membrane wrapped around axons

Who makes myelin?

CNS: oligodendrocytes

PNS: neurolemmocytes

Why are unmyelinated axons slow?

Current leaks out and must be regenerated

What does myelin do?

Insulates the axon, keeps current inside

much faster conduction