Dendrites: like soma but lack golgi complexes, major receptive region
soma (perikaryon): contain free and RER (Nissl bodies), neurofilaments (LM: Ag stain), nucleus with nucleolus, microtubules, mito
axon: most neurons have one, can reach 1 meter, non-tapering, transmits signals, contain neurofilaments, mito, but lack polyribosomes
axon hillock: where axon leaves soma, no free or RER, where AP begins
axonal transport: polyribosomes are in dendrites and soma but not in axon thus this process transfers newly synthesized materials to the axon terminal
synapse on cell body (axonal-somatic), dendrites (axonal-dendritic), axons (axonal-axonal)
Classes
multipolar: more than 2 cell processes
bipolar: one dendrite and one axon
pseudounipolar: one process that divides into 2 processes
Nissl stains: cationic stains, bind to RER and polyribosomes (dend and somas, not axons)
Osmium stain: stains myelinated regions
neurofilaments stain with heavy metals (Ag)
neuropil: interconnections occurring in periphery (ie in gray matter of spinal cord)
Synapses
: convert electrical stimuli Þ chemical signals
axon to dendrite
axon to muscle (neuromuscular junction): ACh, acetylcholinesterase (breaks down ACh)
electrical synapse: nerve cells linked by gap junctions, allow passage of ions directly
PNS vs CNS
CNS
Brain, retina and spinal cord
Segregated into gray matter (soma) and white matter (axon); glial found in both
Spinal cord: center is gray (central canal lined with ependymal cells), periphery is white
Brain: center is white, periphery is gray
Nucleus = group of neuron cell bodies; Tract (column) = bundle of fibers
PNS
composed of ganglia (group of neuron cell bodies) – sensory ganglia such as dorsal root ganglia and autonomic ganglia (sympathetic and parasympathetic ganglia)
ganglia = groups of cell bodies assoc with satellite cells surrounded by fibroblastic capsule
nerves = bundle of fibers; nerves are surrounded by connective tissue
epineurium: outermost connective tissue, surrounds 1 or more nerve bundles, may contain blood vessels
perineurium: within the nerve and surrounding each nerve bundle, ionically permeable sheath
endoneurium: collagen fibers which enclose nerve fibers and their assoc schwann cells
Glial Cell Structure and Function
CNS:
astrocytes
largest of neuroglia; spherical; processes contact capillaries, brain, spinal cord