Corticomotor system Flashcards
What is the first event of the three that preceded voluntary motor movement?
Perceptual mechanisms generate a sensory model of the external world and a person’s position in the environment
What is the second event of the three that preceded voluntary motor movement?
Cognitive processes use the internally generated model to decide on a course of action
What is the third event of the three that preceded voluntary motor movement?
The selected motor plan is conveyed to the neural areas responsible for implementation of the plan
What are the areas of the motor cortex?
- Primary motor cortex
- Supplementary/motor cortex
- Cingulate motor cortex
- Frontal eye fields
What is the function of the reticulospinal tract?
are medial system motor pathways for control of axial and proximal muscles
What is the function of the rubrospinal tract?
part of lateral system motor pathways to control mainly distal and proximal muscles of the upper extremity. (monkeys)
Where does the red nucleus receives most of its innervation from?
cerebellum and primary motor cortex
The rubrospinal tract go where?
Flexors of the hands
Which lobe is the frontal eye field located in?
Frontal lobe
Neurons in the frontal eye field will collaborate with cells where to control eye movement?
Superior colliculus to PPRF
OR
straight to PPRF (horizontal gaze centers)
What is the route of the motor system innervation?
Parietal, premotor/supplementary cortex
Primary motor cortex
Brainstem
Spinal cord
Corticobulbar tract = what tract?
Corticonuclear (same thing, different name)
What is significant about the way the upper and lower parts of the facial nucleus is innervated by UMNs?
Upper part get bilateral projections
Lower part only contralateral
True or false: Corticorubral fibers and corticoreticular fibers are also part of the corticonuclear tracts
True
Corticonuclear fibers pass through what part of the internal capsule on their way to the brainstem? What is the next part?
Genu, then crus cerebri
Motor control of the extraocular eye muscles is partially via a projection from what two cortical areas?
the frontal and parietal motor eye fields of the cortex
the frontal and parietal motor eye fields of the cortex send projections where to innervate the eyes?
the horizontal and vertical gaze centers of the reticular formation
What are the two ways of smiling?
Pyramidal system
RF
What is the pathway for the pyramidal smiling?
Cortex to pyramids to facial nucleus
What is the non-pyramidal pathway for smiling?
Forebrain/hypothalamus to the facial nucleus
Where does the corticospinal tract cross?
Lateral crosses in the medulla
Anterior crosses at the spinal cord level
What percent of fibers of the corticospinal tract cross in the medulla, to form the lateral corticospinal tract?
90%
Where do the fibers of the lateral corticospinal tract synapse (on what neurons)?
Anterior horn nuclei to distal limbs for fractionated movements
What percent of fibers of the corticospinal tract do not cross in the medulla, but instead stay anteriorly to form the lateral corticospinal tract?
10%
What is the function of the anterior corticospinal tract?
Motor innervation to the trunk, neck, and shoulder
True or false: the corticospinal tract is only involved in motor functions
False–has sensory, to emphasize movement
What is the origin of the lateral corticospinal tract?
Frontal cortex, and somatosensory cortex
What is the origin of the anterior corticospinal tract?
only the motor cortex
What type of movement is the lateral corticospinal tract necessary for?
Fractionated movements of the hand and fingers
Why can we not (physically) perform experiments on humans to cut the corticospinal tract?
Intermingles with the rubrospinal tract, thus no way to isolate it
How is the motor cortex fibers organized?
According to a given task, rather than a specific muscle
Can somatotopic organization of the motor cortex change?
yes
What artery gets the leg area of the primary motor cortex?
anterior cerebral
What artery supplies the trunk, hand, and face area of the primary motor cortex?
Middle cerebral
Lesions restricted to the primary motor cortex can cause what?
Persistent hypotonia or spasticity if other cortical areas involved
What are the arteries that supply the internal capsule (branches of the middle cerebral)?
Lenticulostriate
What is paresis?
Weakness of voluntary muscle
What is the role of the premotor area?
Goal directed movement that requires sensory information about the environment
What a mirror neurons?
Neurons in the premotor area that might encode the intentions and actions of others and participate in imitation learning
What are the functions of the premotor cortex compared to the supplementary motor cortex?
PM more important for movements activated or guided by external stimuli
What is the role of the supplementary motor cortex? (2)
Planning or preparing for sequential motor acts.
Coordinating movements from each side of the body
(especially those initiated or controlled by internal, remembered or self-determined stimuli)
What area of the brain has been implicated in the inability to start activities like walking parkinsons?
Putamen
Do lesions of the SMC produce paralysis?
No, but do cause problems in initiating or suppressing movement
What is the function of the frontal eye field?
INfluences eye movements through projections to the brainstem vertical and horizontal gaze centers and the superior colliculus
What is the input to the frontal eye field?
visual association cortex and basal ganglia and thalamic relays about the location of a visual target
What are the three projections that the frontal eye field sends off to help eye movement?
projections to the brainstem vertical and horizontal gaze centers and the superior colliculus.
What is the input to the FEF?
from visual association cortex and basal ganglia and thalamic relays
What is the effect of a lesion in the FEF?
Permanent deficit in the ability to make saccades that are not guided by an external target
Cannot voluntarily direct their eyes away from a stimulus in the visual field
Where do the cortical influence over eye movements go (which nucleus) to have an effect on the eyes?
Pontine RF
What are saccades?
Small movements of the eye
What part of the brain is involved in the reflexive saccades?
Superior colliculus
What is Brown-sequard syndrome?
Hemisection of the spinal cord
Fasciculations and fibrillations are characteristics of UMNs or LMN lesions?
LMNs
If there is a brainstem lesion to the UMN in the spinal cord which side will be affected?
Contralateral
If there is a brainstem lesion to the LMN in the spinal cord which side will be affected?
Ipsilateral
What are the deficits of Brown-Sequard syndrome ipsilateral to the lesion?
Loss of fine touch, UMN symptoms below lesion, LMN signs at level of lesion
What are the deficits of Brown-Sequard syndrome contralateral to the lesion?
Loss of pain and temp sensation
UMN lesion will produce what symptoms in the Babinski response?
Upgoing response (extension of the great toe, and flaring of the other toes)
A lesion to the corticospinal tract / corticonuclear tract origin will produce weakness where?
Facial weakness ipsilateral
Limb paralysis contralateral
What is alternating hemiplegia?
is caused by pontine lesions which involve corticospinal tract fibers and fibers from the abducens nucleus.
What type of lesion will affect one entire half of the body?
Hemispheric lesion
What type of lesion will affect ipsilateral face and contralateral side of the body?
Brainstem lesion
Lesions restricted to the primary motor cortex cause what symptoms?
Persistent hypotonia
