01/30/26 - Nervous Tissue part a (cont)

last day/part for part a

astrocytes

are the largest and most numerous neuroglia in the CNS

• are star shaped glia; have many slender cytoplasmic processes

functions of astrocytes

• maintains the blood brain barrier (BBB)

• creates a 3D framework for the CNS

• repairing damaged nervous tissue

• guiding neuron development

• controlling the intersitial environment

ependymal cells

line the ventricles and central canal, forming a simple cubodial to ciliated epithelium

• the cilia help to circulate the CSF in the third ventricle of the brain

• assist in producing and monitoring CSF

ventricles

in several regions of the brain, these are fluid-filled chambers

central canal

fluid-filled passage along the longitudinal axis of the spinal cord

cerebrospinal fluid (CSF)

fills and circulates among the central canal of the spinal cord and ventricles in the brain

oligodendrocytes (also known as: oligodendroglia)

type of neuroglia whose main function is to provide the myelin sheaths to axons in the CNS

myelin sheaths

forms segments along the axon’s length

meylination

supports and insulates the axons

internodes (segments)

the areas of the axon that are wrapped in myelin

• nothing happens here

nodes of ranvier (gaps)

the small gaps that separate adjacent segments/internodes

• everything happens here

white matter

regions dominated by myelinated atoms

grey matter

areas containing neuron cell bodies, dendrites, and unmyelinated atoms

microglia

• the least numerous and smallest microglia in the CNS

• are phagocytic cells

• their slender processes have many fine branches

• migrate through nervous tissue, acting as janitors, and police force by engulfing cellular debris, waste, and pathogens

satellite cells

surround neuron cell bodies in the ganglia

• regulate the intersitial fluid around the neurons, much as astrocytes do in the CNS

schwann cells (or neurolemmocytes)

form either a thick, myelin sheath or indented folds of plasma membrane around multiple axons of multiple neurons

neurolemma

outer surfaces of schwann cells

• shields the axon from contact with intersitial fluids

demyelination

the progressive destruction of myelin sheaths, both in the CNS and the PNS

• results in a loss on sensation and loss of motor control