PNS lecture Flashcards
(27 cards)
what does a NCV test measure?
used to measure the speed of electrical conduction through a nerve
If there is a deficit, what does this NCV test help with determining?
it can help determine if any nerve damage or destruction exists.
what is the first step in measuring NCV?
use the median nerve and test the time it takes for a stimulus to traverse the nerve along two different distances and get the difference between them (T2-T1)
what is the second step in measuring NCV?
Divide the distance between the two locations (D/T2-T1) to find the actual conduction velocity
In testing motor where do you stick the stimulators and recorders?
recording electrode is placed on the skin over the abductor pollicis muscle
nerve then receives mild electrical stimulation at the level of the cubital fossa, and the time is recorded until the abductor pollicis muscle contracts
In testing sensory where do you stick the stimulators and recorders?
skin of the finer may receive stimulation with recording electrodes placed near the nerve at the wrist and cubital fossa.
If there is a lesion of the motor neuron soma then what observations should be seen?
little/no change in motor
no change in sensory
if there is a lesion of the peripheral nerve what observations should be seen?
Compression –> slowing of motor and sensory
Demyelination –> marked slowing of motor and sensory
Mild Axonal Degeneration –> slight/no reduction
If there is a lesion of the NMJ and or muscle what observations should be seen?
No change in sensory or motor
Peripheral nerve damage develops at the innermost structures first and works toward the outermost structures, name the structures.
Most Vulnerable to Damage: Axon –> Endoneurium –> perineurium —> epineurium
what is carpal tunnel syndrome?
compression of the median nerve at the wrist due to swelling wrist tendons which eventually compress the nerve. (reduction in tunnel size)
what are some of the symptoms associated with carpel tunnel syndrome?
pain, weakness, and numbness in the hand and wrist occur and radiate up the arm
who are most at risk to developing carpal tunnel syndrome?
middle aged females (Esp due to over use)
what does Axotomy mean?
after nerve injury where axons are ruptured/cut, several mechanisms might occur
what is wallerian degeneration?
degeneration of the distal part of the axon ( terminal degeneration)
what is the anterograde transneural degeneration
degeneration of the distal nerve
what is retrograde transneural degeneration?
degeneration of the proximal nerve
After dissection of a peripheral nerve, what happens?
terminal end sprouts
what happens after terminal end sprouting?
one of the sprouts will find the guide tube created by Schwann cells and the axon will continue to grow
What is the growth of the peripheral nerve facilitated by?
nerve growth factor (schwann cells), laminin and adhesion molecules
Once the new axon is grown what is the final step?
schwann cells will redevelop and remyelinate the newly grown axon
why does regeneration/remyelination in the CNS not occur?
oligodendrocytes do not release nerve growth factor
what is Gliosis?
astrocytes multiply in regions of trauma which create glial scars and stop the development of axonal sprouts
what is released in the CNS that opposes axonal regeneration in adults?
inhibitory chemical messengers are released in the CNS
