Motor system Flashcards
Describe the structure of the neuro system
CNS is brain
PNS is rest
PNS splits into Afferent sensory system (Info from body to brain) and efferent motor system (brain to body)
Then motor system splits into somatic and autonomic
Autonomic splits into symp and parasymp
What is classified as a lower motor neuron?
The spinal motor neuron innervating the muscle
What is classified as upper motor neuron?
The direct and indirect pathways leading to innervation of muscle
What are descending motor pathways?
pathways that carry info from cortex to lower motor neuron
what is the final motor pathway?
pathway that carries info from lower motor neuron to muscle
where in spinal motor neuron are neurons that fire to distal muscles?
more laterally
where are neurons that fire to trunk muscles
medial
where are neurons that fire to extensor muscles
ventral
where are the flexor muscles located?
dorsal
what is the ratio of alpha and beta neurons in ventral horn
70:30
are alpha and beta neurons myelinated?
yes
size of alpha motor neurons? beta?
12-20 microns
2-8 microns
Conduction velocity of alpha neurons? beta?
70-120
10-50
Function of extrafusal alpha neurons?
increase in muscle force
function of intrafusal beta neurons?
contractile properties of spindles
Properties of slow (red) motor unit?
high mitochondrial potential, long contractions,low tension in muscle, high oxygen consumption, low fatigue
properties of fast (white) motor unit
Low mitochondrial potentialm short contractions, high tension in muscle, low oxygen consumption, high fatigability
which motor units are recruited first?
slow and then fast (larger) when slow is fatigued
What is the funciton of the primary motor cortex?>
performance of voluntary skilled movement
Upper motor neurons can have direct or indirect pathways
True
What are the two pathways of the direct upper motor neurons?
Lateral corticospinal tract
Medial corticospinal tract
What is the corticobulbar tract?
a corticospinal tract that innervates both hemispheres with the exception of facial and hypoglassal nerves
discuss why facial nerves are an exception of bilateral innervation
Upper facial nerves are normal and get innervated bilaterally the lower facial nerves are only innervated by on side
what happens to face if there is a facial nerve lesion?
contralateral upper and lower facial nerves will be affected (entire half of face will be off)
