Peripheral Nervous System And Skeletal Muscles Pathology Dr. Martin Flashcards
motor unit consists of
axon,
lower motor neuron,
muscle fibers
peripheral nerve consists of
nerve fiber + myelin, schwann cells ( have nodes of ranvier, each schwann cell covers 1 internode)
Epineurium
encloses entire peripheral nerve
Perineurium
multilayered concentric CT that encloses each fascicle
Endoneurium
surrounds each nerve fiber
Axonal degeneration involves and does what
axon and neuron , can cause axon regeneration and reinnervation of muscle
Segmental Demyelination
myelin breakdown in segments
denervation atrophy vs myopathy
- denervation atrophy : loss of axon causes atrophy of muscle
- Myopathy : abnormal muscle fiber itself
segmental demyelination of schwann cell vs myelin sheath
- schwann cell : hereditary or sensory neuropathy
2. myelin : guillain barre
denuded axon
remyelination signal (new myelin in shorter in length then normal myelin)
cross section of thin myelin on a nerve looks like
onion cut (onion bulb)
Traumatic neuroma
axons that cant find their distal target (muscle) = pseudotumor made (non-neoplastic whorled proliferation of axonal processes and
= CAUSES PAINFUL NODULE
Wallerian degeneration
focal lesion in axon (distal part of axon is damaged
Axon damage
from ischemia or trauma = whole neuronal body or its axon
axonal degeneration
primary destruction of axon and myelin
axonal degeneration steps of what happens after
- Myelin Ovoids : schwann cells catabolize myelin + later engulf axon fragments = oval compartment made
- M clean them up
- proximal part of severed nerve degenerates in 2-3 distal internodes
- regenerates
axonal degeneration shows what SIGNS on histology of nerve
- Denervation Atrophy
- Angulated ends (smaller and triangle shaped muscle fibers
- Target Fibers
what determines the fiber type
motor neuron
group atrophy
a type group (muscle fiber type) gets denervated
type 2 fiber atrophy can happen from
= inactivity
= diffuse (limb fracture, pyramidal tract degeneration, neurodegenerative dz)
= STERIOID MYOPATHY (from glucocorticoids)
- hypertrophy does what to muscle fiber
and 2. segmental necrosis
- splitting of fiber (from increased exercise = fibers split)
- deposits of collagen and fat
Regenerated nerves stain how
cytoplasm laden with RNA = RED trichrome stain
somatic motor function travel how
- lower motor N on ANTERIOR HORN
2. to muscle fiber
Somatic Sensory nerve travels how
- distal nerve ending (specialized sensory structures) pick up signal
- travels with peripheral N to DORSAL ROOT GANGLION
- go to brain to synapse at SPC and brainstem
Autonomic nerve fiber problems involves what disease
Diabetic neuropathy
unmyelinated fibers
temp and pain = slow conduction
large axon with myelin
light touch, motor signals
= fast conduction
Axonal Neuropathy
- targets what never usually and causes what
- physiologic hallmark
- longest neuron = dying back progression
2. reduction of amplitude, PRESERVATION of conduction velocity
electrophysiologic hallmark of demyelinating neuropathy
SLOWED nerve conduction,
Neuronopathies
destruction of neurons (infection Herpes Zoster, Toxins platinum)
= effects proximal and distal body equally (HALLMARK)
peripheral neuropathy SX
- tingling, stabbing, buring, or pins and needles
peripheral neuropathy : polyneuropathies
- many nerves usually symmetric
- starts distal and ascends
- hands involved usually at level of knee (stocking and glove)
Mononeuritis Multiplex :
many nerves damaged in haphazard distribution
VASCULITIS —> Polyarteritis nodosum PAN
mononeuropathies
single nerve effected
Bell’s Palsy
- effects what
- age
- SXX
- CN 7 mononeuropathy (facial muscle paralysis)
- 15-60yo (resolves spontaneously)
- one side facial droop , facial tingling, headache + neck pain, memory prob, balance issues, SAME side limb paresthesias, low tears tasting saliva)