Nerve Anatomy Flashcards
Innervation ratio
number of muscle fibers one axon innervates.
Muscle fibers : 1 axon
innervation ratio of gross vs fine movement
gross movement has a high IR (lots of muscles innervated by one axon).
Fine movement has a low IR (less muscles innervated by one axon).
innervation ratio and force generation
the higher the IR, the greater the force generated by the motor unit
myotome
group of muscles innervated by 1 spinal segment
what motor neuron innervates extrafusal fibers
alpha-motor neurons
what motor neuron innervates intrafusal fibers
gamma-motor neurons
2 types of intrafusal fibers
Nuclear bag and nuclear chain
3 layers of nerve connective tissue, from out to in
- Epineurium
- Perineurium
- Endoneurium
renshaw cell
inhibitory interneuron
three types of motor neurons
- alpha
- beta
- gamma
what type of motor neuron does needle EMG evaluate?
alpha motor neurons
what fibers does each type of motor neuron innervate
- alpha = extrafusal
- beta = extrafusal and intrafusal
- gamma = intrafusal
what does the henneman size principle say?
small alpha motor neurons are recruited first during voluntary contraction and large alpha motor neurons are recruited later when more motor units are needed to generate contraction.
correlation between size of alpha motor neuron and threshold of excitation
small alpha motor neurons have a low threshold.
large alpha motor neurons have a high threshold.
3 different types of muscle fibers
Type 1
Type 2a
Type 2b
