DPT 712: NERVE CONDUCTION STUDIES EXAM QUESTIONS AND ANSWERS WIT COMPLETE SOLUTIONS
What are A alpha nerve fibers?
Innervate extrafusal skeletal muscles
What are A gamma nerve fibers?
Innervate intrafusal fibers muscle spindle
What are B nerve fibers?
Pre-ganglionic ANS
What are C nerve ...
,Glycoprotein fatty substance made by Schwann cells wrapping themselves around the
axon.
What are the two purposes served by myelin surrounding the nerve?
1. Increase speed of conduction by forcing the axon to conduct action potentials via
saltatory conduction. Jumping from an area of no myelin to the next area of no myelin.
2. Protects the nerve, just like fat protects us
What comprise the majority of sensory nerve fibers in peripheral nerves?
Unmyelinated fibers compose 75% of the axons in peripheral nerves
What is the epineurium?
Most external connective tissue covering of a nerve which is a dense protective
covering that envelopes the nerve along its entire length
Where in the body is the thickness of the internal epineurium typically greater?
Where peripheral nerves span joints and where greater compressive forces are applied
What is the perineurium?
Intermediate connective tissue covering that is loose around groups of axons called
fascicles. It creates a diffusion barrier similar to the blood-brain barrier, and maintains a
positive intrafascicular pressure and protects against infection
What does the perineurium's looseness around fascicles of axons allow axons to
do?
This way axons can leave one group of axons (fascicle) and enter another
What is the endoneurium?
Fine connective tissue covering around individual axons
Which connective tissues cover peripheral nerves?
, Epineurium, perineurium, and endoneurium
What connective tissues cover spinal nerve roots?
Only endoneurium, making them more vulnerable to pressures
What is the vasa nervorum?
Longitudinal system of blood vessels within the nerve that provides circulation to each
of the layers within the nerve. Each fascicle is well vascularized
What can damage to a nerve fascicle's blood vessel's endoneurium induce?
A miniature closed compartment syndrome, where a lack of blood to endoneurial
structures leads to edema within the fascicle (intrafascicular edema). The perineurium
resists the expansion of the edema and places pressure on the axons in the area,
compressing them and causing an injury to the nerve
How do local arteries affect nerves?
By supplying the surface of the nerves and forming plexi around the epineurium
How do obliquely directed feeder branches affect nerves?
By penetrating into the perineurium and forming another plexus, and by penetrating the
endoneurium to form capillary beds that run the length of the axon
What surrounds each and every axon myelinated or not?
Endoneurium
What is the consequence of edema present around and into the epineurium?
The perineurium works as a diffusion barrier protecting the intrafascicular environment
and allowing axons to transmit APs normally
What is the consequence of edema present inside the perineurium from 2nd
degree virus, compression, etc?
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