Motor Cortical Areas Flashcards
What are the 4 motor cortical areas?
primary motor cortex
premotor cortex
supplementary motor cortex
frontal eye fields
What are the 3 general deficits you’ll see in motor cortical area damage?
loss of voluntary movements
paresis
increased tone/stretch reflexes
What are the 2 criteria for an area to be considered a motor cortical area?
- cytoarchitecturally has to be agranular
- stimulation of the area must evoke motor movement even at low stimulus intensities
What does it mean that the area is agranular? What areas are granular?
motor areas are agranula because the granular layers (2 and 4) are underdeveloped and the pyramidal layers (3 an 5) are well developed
sensory areas are granular
What are the two general opinions about what the primary motor cortex does?
- controls indibidual muscles/forces by generating the motor command
- Controls the more global features of movement, like direction and amplitude of reach
What two structural features of the primary motor cortex have been revealed by stimulation?
1, motor homunculus
- columnar organization - so within areas of representation for the thumb, there are columns that deal with specific movements of the thumb - specific spot for flesion, specific spot for adduction, etc.
this allows for very discrete movements
Where does the afferent input FROM THE PERIPHERY to the primary motor cortex come from?
from the periphery bia the dorsal column nuclei (DCN) and VPL of the thalamus
- from joints
- from the spindle receptors
- and cutaneous input form the glaborous skin
What brain regions provice afferent infromation tot he primary motor cortex?
cerebellum
basal ganglia
somatosensory cortex
premotor
supplementary motor
posterior parietal cortex
What brain region in particular provides visual info to the primary motor cortex for spatial cognition
posterior parietal cortex (areas 5 and 7)
What is the primary output projection from the primary motor cortex?
mostly through pyramidal neurons in the pyramidal tract
(which drops off innerfation at areas like the premotor, supplementary motor, somatosensory, frontal eye, etc. and then becomes the corticospinal tract)
About how mnay axons make up the pyramidal tract?
2,000,000!
While many textbooks say the pyramidal tract is made primarily of the giant Betz cells in area 4, what is the actual percentage?
only 3%
Pyramidal cells going to the basal ganglia run in what tract?
corticostriate
Pyramidal cells going to the red nucleus go in what tract?
the corticorubral tract
Pyramidal cells going to the pons travel in what tract?
the corticopontine
Pyramidal cells going to the reticular formation travel in what tract?
corticoreticular tract
Pyramidal cells going to the cranial nerve nuclei travel in what tract?
corticobulbar
Pyramidal fibers going to the spinal cord travel in what tract?
corticospinal
The corticobulbar fibers specifically go to which 5 nuclei?
- motor trigeminal
- facial nucleus
- nucleus ambiguus
- spinal accessory nucleus
- hypoglossal nucleus
Are the fibers to the motor trigeminal mostly bilateral, ipsilateral or contralateral?
mostly bilateral
How is innervation of the facial muscles a bit odd in terms of bilateral, ipsilateral or contralateral?
lower face is controlled by the contralateral nucleus ONLY
Upper face is controlled by both ipsilateral and contralateral motor cortex
so central damage will spare the forehead
What muscles ar einnervated by fibers in the nucleus ambiguous? Bilateral, ipsilateral or contralateral?
muscles of th elaryngeal and upper airways - bilateral
Is innervation form the spinal accessory nucleus bilateral, ipsilateral or contralateral?
ipsilateral
Is inenrvation from the hypoglossal nucleus bilateral, ipsilateral or contralateral?
mostly contralateral
so with central damage, the tongue will project away from the side with the lesion