Topic 16 - PNS Injuries 1 Flashcards
The myeline sheath in peripheral nerves consists of _______ _____ wrapped around individual axon fibres.
Schwann Cells
The outermost membrane of an individual nerve fibre in the PNS.
Neurolemma
Gaps between the Schwann cells.
Nodes of Ranvier
When impulses travel faster along myelinated fibres than along unmyelinated ones.
Saltatory Conduction
What are the 3 additional connective tissue layers that axons are covered by?
1) Endoneurium
2) Perineurium
3) Epineurium
A connective tissue layer surrounding individual axons.
Endoneurium
A connective tissue layer surrounding bundles of axons.
Perineurium
A connective tissue layer surrounding the entire peripheral nerve.
Epineurium
T/F - Peripheral nerves carry predominately afferent information and not efferent information.
False - Peripheral nerves carry predominately BOTH afferent and efferent information.
________ refers to sensory or proprioceptive information and ________ refers to motor information.
Afferent
Efferent
Some peripheral nerves carry _________ fibres, such as the ___________ outflow from T1-L2 and the _______________ outflow from S2-S4.
Autonomic
Sympathetic
Parasympathetic
Common causes of peripheral nervous system ________ damage include:
- Direct trauma
- Infection
- Compression
- Injury repair complications
- Poison/toxins
- Diseases causing peripheral neuropathies
- Birth trauma
- Loss of blood supply
- Extremes of temperature/radiation
Neuronal
T/F - The most common cause of PNS neuronal damage is compression.
False - The most common cause of PNS neuronal damage is DIRECT TRAUMA.
A common cause of PNS neuronal damage resulting from:
- Severance or crush injuries (e.g. MVAs, industrial accidents)
- Traction injuries (e.g. stinger/burner)
- Forcible overextension of a joint or repeated small traumas
Direct Trauma
A common cause of PNS neuronal damage due to the presence of a pathogen (e.g. infective neuritis).
Infection
A common cause of PNS neuronal damage resulting from:
- Improper immobilization
- Poorly fitted crutches
- Prolonged cane/walking frame/wheelchair use or inadequate padding
- Carpal tunnel syndrome, TOS, compartment syndromes, meralgia paresthetica, tumors & prolonged postures
- Prolonged pressure at bony prominences (e.g. sleep, intoxication, bicycle riding)
Compression
A common cause of PNS neuronal damage resulting from:
- Nerve is tractioned or compressed by bony calluses (e.g. dinner fork deformity d/t Colles fracture)
- Nerve is caught up in restrictive scar tissue
- Nerve is entrapped in a damaged joint or bone (e.g. shoulder dislocation)
- Iatrogenic inflammation
Injury Repair Complications
A common cause of PNS neuronal damage resulting from:
- Alcoholism
- Occupational contact with chemicals/abuse of chemicals
Poisons/Toxins
A common cause of PNS neuronal damage resulting from:
- Diabetes
- AIDS
- Poliomyelitis
- Hansen’s Disease (aka. Leprosy)
Diseases Causing Peripheral Neuropathies
A common cause of PNS neuronal damage resulting from:
- Erb’s palsy
- Klumpke’s palsy
Birth Trauma
A common cause of PNS neuronal damage resulting from:
- Extreme edema
- Frostbite
Loss of Blood Supply
T/F - A common cause of PNS neuronal damage is from radiation or extremes in temperature, especially hot.
False - A common cause of PNS neuronal damage is from radiation or extremes in temperature, especially COLD.
The process that occurs when an axon/nerve fibre is cut, severely tractioned to the point of separation, or crushed. It can also occur when axons sustain severe and prolonged compression.
Wallerian Degeneration (aka. Anterograde Degeneration)
