ASTROCYTES

"nursing neurons"
Many processes
Maintain proper balance of K+ for generation of nerve impulse
Participate in neurotransmitter metabolism
Participate in brain development by assisting migration or neurons

Provides link between neurons and blood vessels

Form blood-brain barrier (BBB)
Regulate entry of substances into brain

BLOOD BRAIN BARRIER

BBB allows diffusion only of lipid soluble substances across the astrocyte membrane surrounding the capillary

Nicotine, ethanol, heroin

Water soluble substances may pass but only by mediated transport

Glucose, amino acids

PARKINSON'S DISEASE

caused by a lack of the neurotransmitter dopamine

normally produced by neurons of the brain

Lack of dopamine causes the characteristic shaking and decreased muscle control

Administration of dopamine is not helpful because it cannot cross the BBB

Administration of L-dopa (a precursor of dopamine)

reduces the symptoms because it can pass the BBB and is converted to dopamine by the CNS neurons

Parkinson's Pre Treatment Movie

Parkinson's Post Treatment Movie

Dyskinesia Movie

MICROGLIA

	Small, phagocytic Derived from monocytes engulf bacteria clear away debris from dead cells may migrate to areas of injured nerve tissue

OLIGODENDROCYTES

	Most numerous glial cell Support neurons by twining around them and producing a lipid protein wrap called a myelin sheath Each oliodendrocyte wraps myelin around several axons

EPENDYMAL CELLS

	Derived from epithelial cells Many may be ciliated Line the fluid filled ventricles of the brain Form cerebrospinal fluid (CSF) and assist its circulation

NEUROLEMMOCYTES

"Schwann cells"
produce myelin sheaths around PNS neuron axons
each cell produces part of the myelin sheath around a single axon of a PNS neuron

SATELLITE CELLS

satellite cells (small arrow)

support neurons in ganglia clusters of the PNS
surround ganglion neuron cell bodies providing nutrients