Peripheral Nervous System Flashcards
Describe the layers of tissue surrounding peripheral nerves. (Outermost to innermost)
Epineurium: outermost covering of a peripheral nerve
Perineurium: middle layer of covering that envelops fascicles/groups of axons and maintain the blood nerve barrier
Endoneurium: Innermost covering that surrounds each individual axon
What is motor unit?
A single motor neuron and all of the muscle fibers it innervates
What is saltatory conduction? What is its purpose?
An action potential moving along an axon in a jumping fashion from node to node
Purpose: Decreases the use of the sodium potassium pump and increases speed of conduction
What structures form the myelin sheath?
Schwann cells
What are the classifications of peripheral nerves?
A fibers
B fibers
C fibers
Describe A fibers.
Large fibers
Myelinated
High conduction rate
Describe B fibers.
Medium fibers
Myelinated
Reasonably fast conduction rate
Preganglionic fibers of the autonomic system
Describe C fibers.
Small fibers
Poorly myelinated or unmyelinated
Slow conduction rate
Postganglionic fibers of the sympathetic system
Exteroceptors for pain, temperature, and touch
What are the subsets of A fibers?
Alpha
Beta
Gamma
Delta
What are 3 types of A fibers? What sensation are they responsible for?
Alpha motor neurons
Muscle spindle primary endings
Golgi tendon organ
Touch
List one example of a beta fiber. What sensations are beta fibers responsible for?
Muscle spindle secondary ending
Touch, kinesthesia
List one example of a gamma fiber. What sensations are gamma fibers responsible for?
Gamma motor neurons
Touch and pressure
What sensations are delta fibers responsible for? (4)
Touch
Temperature
Pressure
Pain
