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PNS
- Somatic- motor & sensory
- Autonomic- S,P, eneteric
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Dendrites
- motor & atonomic have
- sensory- pseudounipolar
- protein synth machinery
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Axons
- lack protein synthesis, must use fast azonal transport to transport things along MT
- MT & mitochondrai (DEVOID of large granules)
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Mylenating Schwannc cell
- Recruited by >=1 micrometer diameter axons
- Neuregulin-determines amt of mylentation
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Nonmylenating cells
- <=1 micrometer diameter axons
- Gathers bundle of axons
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Satellite cell
- around cell body & proximal dendrites
- Barrier to enter cell body
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Perineurium
BBB- tight junctions
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Endonerium
- also BBB in capillaries- tight junctions
- Schwann cell (more abundant than fibroblasts)--> synthesize collagen
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Nodes of Ranvier
- high Na and K channels
- Devoid of myelin
- Where collateral axon branches come off
- In PNS-> reduced diamerter at nodes
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Schmitt-Lantermann Clefts
Periodic spaced Schwann cell
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Dorsal root ganglion
- heterogenous in size and function
- Largest: touch-sensitive, myelinated axons
- Smaller- pain fibers, unmyelinated
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Sensory neurons
- Pacinian corpuscle: sensitive to touch, a single axon surrounded with myelin by modified Schwann cell until reaches corpuscle- surrounded by CT and fluid
- Non-encapsulated (free) endings: not surrounded by CT sensitive to pain.
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Motor Neurons (efferents)
- Alpha motor neurons- largest, longest, mylenated
- Gamma motor neurons- small, unmyelinated (<1 um)
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Autononmic NS
- S:
- "forf"
- dependent on Nerve Growth Factor (NGF)
- P: fine tune and maintain norma function
- E: receive input from S&P but autonomous, reg gut, AUerbach's and Meissner's plexus, enetic glial cells
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Lenghts of ganglia in S&P
- S: pre->short post->long
- P: pre->long post->short (ganglia close/on target)
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