motor control part 1 Flashcards
greater than 1/2 of the primary motor cortex controls what?
hands and speech
what area is anterior to the lateral portions of primary motor cortex below supplemental area?
premotor area
the premotor area projects to?
1 degree motor cortex and basal ganglia
what area is superior to premotor area lying mainly in the longitudinal fissure?
supplemental motor area
what movements do the premotor and supplemental motor areas provide?
attitudinal movements
fixation movements
positional movements of head and eyes
background for finer control of arms/hands
what percentage of the corticospinal tract originates in the primary motor cortex?
30%
what percentage of the corticospinal tract originates in the premotor and supplemental areas?
30%
what percentage of the corticospinal tract originates in the somatic sensory areas?
40%
where does the corticospinal tract descend?
via the posterior limb of the internal capsule (btw caudate and putamen)
what does the corticospinal tract form?
pyramids of the medulla
when corticospinal tract fibers cross midline they form?
lateral corticospinal tract
when corticospinal fibers stay ipsilateral they form?
ventral corticospinal tract
when all tracts are cut and the cord is completely isolated from the brain its called? Low
spinal preparation
flaccidity!
when you have a transection at the mid collicular level mid brainstem its called?
decerebrate preparation
rigidity!
destruction of the cerebral cortex/ high brain stem is called?
decorticate preparation
different type of rigidity- spasticity
which brainstem area that receives stimulation from the vestibular nuclei and transmits excitatory signals to stimulate the axial trunk and extensor muscles that support the body against gravity?
pontine reticular nuclei
which brainstem area that receives strong input from the cortex, red nucleus, and other motor pathways and transmits inhibitory signals to the same antigravity muscles via the medullary (lateral) reticulospinal tract
medullary reticular nuclei
with regard to postural control, if DESCENDING cortical signals are blocked, what is the expected result?
increased extensor tone, flexors repressed- decerebrate rigidity
what is the function of a dynamic signal from pyramidal cells to alpha motor neurons?
initiation of muscle contraction
what is the function of static signal from pyramidal cells to alpha motor neurons?
fires at a slower rate to maintain contraction after initiation has occurred
what some important characteristics of postural reflexes?
- impossible to separate from voluntary movements
- they maintain body in an upright position
- maintain stable postural background for voluntary movement
extension of the neck facilitates extensors of?
arms and legs
flexion of the neck facilitates flexors of?
arms and legs
rotation of the neck facilitates extensors ______ and inhibits flexors ______
ipsilateral; ipsilateral
rotation of the neck facilitates flexors ______ and inhibits extensors _________
contralateral; contralateral
at the onset of clockwise rotation (to the right) what would you expect happens in the VIII cranial nerve on the left side?
decrease in firing rate
stimulation of semicircular canals is associated with?
increased extensor tone
nystagmus
slow component- tracking nystagmus is initiated by
semicircular canals
fast component- jumping ahead nystagmus is initiated by
brain stem nuclei
after 20 clockwise rotations with eyes closed on a revolving stool, the subject is abruptly stopped and the eyes are opened. what is observed?
lateral nystagmus with slow component clockwise
what are 3 disorders involved with the basal ganglia?
tremor and other involuntary movements
changes in posture and muscle tone
poverty and slowness of movement
motor functions of the basal ganglia are mediated by the?
motor areas of the cortex
what are the 2 circuits of the basal ganglia?
caudate
putamen
caudate + putanem =
striatum
what is a lesion in the globus pallidus?
athetosis- spontaneous and continuous writhing movements
what is a lesion in the subthalamus?
hemiballismus- sudden violent and flailing movements
what is multiple small lesions in putamen?
chorea- flicking movements in hands and feet
rigidity, akinesia and resting tremors happen in?
substantia nigra- Parkinsons
in backward sway, what is the distal to proximal sequence of muscles?
tibialis- quad- abdominal
in forward sway, what is the distal to proximal sequence of muscles?
gastrocnemius- hamstring- paraspinals
what would happen to a repetitive simple stretch reflex, if when a muscle contracts it destabilizes posture?
it would be inhibited
what would happen to a repetitive simple stretch reflex, if when a muscle contracts it stabilizes posture?
it would be facilitated
ones sense of upright is generally a combination of cues that include both visual and vestibular information, true or false?
true- CN VIII connected to CN III, IV, VI
what effect does the striatum have on the substantia nigra?
inhibitory GABA projections
a stroke that lesions the posterior limb of the internal capsule (between putamen and caudate) would be associated with?
loss of voluntary movement
when supine, head tilt is best detected by what?
saccule
what plays an important role in determining orientation of the head when person is upright?
utricle
what plays an important role in determining orientation of the head when person is lying down?
saccule
signals from neck proprioceptors typically OPPOSE signals from the vestibular apparatus as the head and neck are rotated and have similar effects on limb flexion and extension. true or false?
true
