Exam 2 Study Guide 5 Flashcards
Demarcation between PNS and CNS
CNS: encased in bone
PNS: not in bone
How are peripheral nerves constructed?
parallel bundles of axons surrounded by 3 sheaths
3 sheaths
- endoneurium
- perinerium
- epineurium
*mesoneurium outside of that
What supplies blood to the peripheral nerves?
Arterial branches that enter the nerve trunk
What structures are supplied by peripheral nerves?
- visceral
- somatic structures
somatic peripheral nerves
usually mixed, consisting of sensory, autonomic, and motor axons
cutaneous branches of peripheral nerves supply
- skin
- subcutaneous tissues
muscular branches of peripheral nerves supply
- muscles
- tendons
- joints
4 nerve plexuses
- cervical
- brachial
- lumbar
- sacral
movement and nerve health
promotes flow of blood through nerves and axoplasm
nerve movements and sheaths
- fascicles glide within the nerves
- nerves glide along with other structures
myopathy
disorder intrinsic to muscles
What remains intact with myopathies?
- sensation
- autonomic function
When is coordination, muscle tone, and reflexes affected with a myopathy?
only when atrophy is so severe that muscle activity can’t be elicited
pins and needles sensations increase with
severity of neuropathy
signs of damage from neuropathy result from
hypoactivity or hyperactivity of neurons
When does severance occur?
when nerves are physically divided by excessive stretching or a laceration
- axons completely interrupted
What happens immediately with severance injury?
- loss of sensation
- muscle paralysis
in area supplied
When would severance result in regrowth/repair?
- if proximal and distal nerve stumps are apposed and
- scarring doesn’t interfere
focal compression of a peripheral nerve causes
traumatic myelinopathy
repeated mechanical stimuli may cause
focal compression
Where does collateral sprouting occur for repair of nerve injury?
proximal stump
What must be the case for regeneration to occur?
PNS only
cell body must be intact
What do Schwann cells do for regeneration?
- myelinate axons
- secrete chaemotactic factors that promote growth and axon guidance
- secrete neurotrophic factors
axon rate of regrowth
1-2 mm per day
What happens if the NMJ fails to function?
- no depolarization occurs
- weakness
- atrophy
MG
- affects NMJ
- damages ACH receptors
- repeated use of a muscle leads to weakness
botulism poisoning causes interference with
release of ACH from motor axons
botulism poisoning causes:
- acute progressive weakness
- loss of stretch reflex
- sensation remains intact
some types of peripheral nerve damages
- sensory changes
- autonomic changes
- motor changes
- trophic changes
types of sensory changes in response to peripheral nerve damage
- allodynia
- dysesthesia
- paresthesia
- hyperalgesia
3 types of peripheral neuropathy
- mononeuropathy
- multiple mononeuropathy
- polyneuropathy
types of traumatic mononeuropathies
- axonopathy
- myelinopathy
- severance
neuropathy vs. myopathy
neuropathy: disorders dealing with damage to axon, myeline sheath, or both
myopathy: disorder intrinsic to muscles themselves
What is a muscular dystrophy? (general)
progressive weakening and wasting of muscle
