Ch. 12: Peripheral NS Flashcards
Peripheral Nerve
- distal axon projections
- After nerve leaves spinal canal
Cervical Plexus
- C1-C4
- motor, sensory, sympathetic to neck and tops of shoulders
Brachial Plexus
- C5-C8, T1
- Motor, sensory, sympathetic to arms
Sacral Plexus
- L4-S4
- motor, sensory and parasympathetic to back and bottom of legs
Damage to spinal nerve causes:
- minor weakness to 1+ muscles
- (b/c Mm are innervated by more than one spinal level)
-sensory loss in dermatomal pattern
Damage to Peripheral Nerve Causes:
- paralysis to 1+ Mm
- (b/c a muscle is only supplied by one peripheral nerve)
-sensory loss in peripheral pattern
Spinal Nerve at risk from:
- bulging disc
- collapse of intervetebral foramen
Lumbar Plexus
- L1-L4
- motor, sensory, sympathetic to front of legs
Principles of a plexus
- one peripheral nerve gets axons from many different spinal levels
- one spinal level sends axons to many different peripheral nerves
Spinal Nerve
- joining of one spinal level
- all sensory, motor and autonomic
- dividing line between central and peripheral NS
- dermatomal/myotomal pattern when damaged
Rami
- ventral
- dorsal
- communicating
Axon Connective Sheaths
- endoneurium
- perineurium
- epineurium
Nerves and movement
- nerves love blood, space and movement
- Movement increases blood flow, facilitates gliding of N, and axoplasmic transport
- nerve axons have wrinkling in endoneurium to allow movement
If nerves can’t move:
the axons stick to connective tissue and shorten
Dysfunction of peripheral Nn
- Sensory changes
- Motor changes
- Autonomic changes
Autonomic changes (peripheral nerve damage)
- decreased function
- decreased sympathetic function
(there is no parasympathetic in peripheral nerves)
NMJ
- EPSP only
- atrophy of denervation if axons die
Sensory Changes
damage to pheripheral nerve
- location depends on where it’s damaged
- depends on how much damage
- Anesthetic/Analgesic or both
Motor damage
to peripheral nerve
- location depends on what’s damaged
- severity depends on how much damage
changes following denervation
- fibrillations
- trophic changes (to nerve, muscle, skin)
Traumatic Axonopathy
- axon and myelin degenerate, but connective tissue tube remains
- Wallerian degeneration distal
- Recovery: good
Axon regrowth rate
1 inch/month
Multiple mononeuropathy
-involves 2+ discrete Nn in different body parts
Classification of peripheral neuropathies
- mononeuropathy
- multiple mononeuropathy
- Polyneuropathy
Traumatic Myelinopathy
- temporary disruption of conduction along axon membrane
- axon intact
- demyelination possible
- Recovery: excellent
- +Tine’s sign (b/c demyelinated areas upregulate mechanoreceptors)
Severance
- axon/myelin degenerate and connective tissue tube is severed
- wallerian degeneration distal
- Recovery: fair
- axons may not find connective tissue tube (can form neuroma)
- may go into other tube and become nonfunctional
Polyneuropathy
- decreased sensory, motor, autonomic starting distal and working to proximal
- no peripheral or dermatomal pattern
Causes of Polyneuropathy
- diabetes
- Alcoholism (nutritional deficiencies)
- autoimmune (guillain barre)
Mononeuropathy Levels
- traumatic myelinopathy
- traumatic axonopathy
- severance
