glial cells, myelination, and regeneration

neuroglia (glial cells) characteristics

protect and nourish neurons; found in CNS and PNS; smaller and more numerous than neurons; capable of mitosis

astrocyte functions

form blood- brain barrier

ependymal cells

ciliated cuboidal epithelial cells that line ventricles of brain and central canal of spinal cord; play a role in production of CSF

microglia

engulf debris within CNS

oligodendrocyte

CNS axon only; wrap themselves around the axons like electrical tape; produce myelin and create myelin sheaths

myelin

insulator of electrical activity

satellite cells

regulate fluid composition around neuron cell bodies; monitor substances around cell body

schwann cells

PNS axons only; wrap themselves around the axons like electrical tape; produce myelin and create myelin sheaths

myelination

process of wrapping the axon with a myelin sheath to electrically insulate it; speeds up communication

saltatory conduction

impulse jumps from one neurofibril node to another

neurofibril node

space on axon where it there is no myelin sheath

continuous conduction

results in slower communication; how unmyelinated axons propagate impulses

axon regeneration

damaged PNS axons can regenerate if the cell body is intact and a critical amount of neurolemma remains; depends upon extent and site of damage

nerve

cable-like bundle of parallel axons

endoneurium

CT surrounding a single axon

perineurium

CT surrounding each fascicle

epineurium

CT surrounding an entire nerve

synapse

specialized junction between 2 neurons or between a neuron and a muscle/gland cell

presynaptic neuron

synaptic knob at axon endings for sending signal; neuron above synapse

synaptic cleft

space between presynaptic and postsynaptic neurons

postsynaptic neuron

neuron after synapse

neuronal pools

neurons grouped into patterns based upon function

multiple sclerosis (MS)

autoimmune diseases where immune system attacks myelin

Amyotrophic lateral sclerosis (ALS)

neurodegenerative disease affecting various motor neurons; loss of function leads to muscle weakness, atrophy, and spastic paralysis; loss of control of all muscle types