Motor Control and the Corticospinal Tract Flashcards
what is the direct pyramidal pathway for
making limbs move
what is the extrapyramidal pathway for
background work keeping us stable, balanced, fluid movement
what is the general pathway of voluntary movement neurons
CNS sends axon down the brainstem to the spinal cord
sometimes uses an interneuron
lower motor neuron leaves the spinal cord and goes into limbs/muscles
what makes a neuron in the pyramidal pathway
whether it goes through the medullary pyramids or not
what does the alpha motor neuron to alpha motor neuron tract look like
decision - motor cortex - spinal cord - muscles
what does the alpha motor neuron to alpha motor neuron tract look like
decision - motor cortex - spinal cord - muscles
if you have to think about a movement what does the pathway look like
decision - pons - cerebellum - thalamus - motor cortex - spinal cord - muscles
what is the pathway involved in making movement smooth
decision - basal ganglia
what type of neurons are upper motor neurons
alpha motor neurons
what type of neurons are lower motor neurons
alpha or gamma motor neurons
what do gamma motor neurons do
monitor muscle spindle sensitivity and judge the baseline level of muscle tone (not overshooting or undershooting)
what are the 2 tracts involved in motor control
lateral and anterior
where do axons leave the cortex from
primary motor cortex, supplementary motor cortex, premotor cortex, sensory cortex (sometimes)
why would neurons leave the sensory cortex
to amplify and upgrade the proprioception information
what is the association cortex for
visually aided movement and to stop/start movement, suppress unwanted movements
describe the movement of the neurons in the corticospinal tracts once leaving the cortex
cortex - corona radiata - posterior limb of internal capsule - midbrain - medulla - lateral/anterior corticospinal tract
how many neurons are in the lateral corticospinal tract and where do they go
85%
go to lateral funiculus in ventral horn and then limb muscles
how many neurons are in the anterior corticospinal tract and where do they go
15%
go to anterior funiculus in ventral horn and split into bilaterally paired neurons to go to midline muscles
where is the damage if there is a lesion on upper motor neurons
on the opposite side of the body
where is the damage if there is a lesion on lower motor neurons
on the same side of the body
which place is the most common place where a stroke will cause quadriplegia
pons
what is paresis
weakness but not full paralysis
what is spinal shock
a period where nothing works
what are the signs when there is upper motor neuron syndrome (stroke)
spastic paralysis, no muscle atrophy, hyperreflexia and clonus, hypertonia, positive babinski syndrome
what causes spastic paralysis
increased activity of gamma motor neurons as they are uncontrolled by damaged alpha neurons
why is there no muscle atrophy in UMN stroke
lower gamma neurons are fine and they nourish the muscle
why does hyperreflexia happen
lower motor neurons randomly firing
what causes hypertonia
gammas are trying to maintain readiness to move and it isnt regulated by alphas
what is babinski sign
extensor plantar response
what are the signs of lower motor neuron syndrome
flaccid paralysis, significant atrophy, visible twitching, spontaneous discharge of motor neurons, hyporeflexia, normal plantar response
