Motor Systems II Flashcards
Motor tract origin
Corticospinal tract
Corticobulbar tract- to brainstem, movement of face
Primary motor cortex
Area 4
Immediately Anterior to central sulcus
Primary motor cortex lesion
Paralysis
Paresis of specific muscle groups
Some recovery of function may occur due to cortical plasticity
Damage depends on part of human homunculus involved
Stroke brain regions
Always involve multiple cortical areas
Stroke involving occlusion of MCA
Affect almost all of one side of frontal lobe
Severe motor disability in all parts of contralateral body except for lower limb (supplied by ACA)
Infraction of proximal M1 segment of MCA
Affect blood supply of basal ganglia via lenticulostriate arteries
Affects blood supply to motor cortex
More disabling than stroke that affects motor cortex (M3) alone
The more proximal an infarction…
The more problems arise
Premotor and Supplementary motor cortex Damage
Areas 6 and 8
Motor Apraxia –> normal reflexes + no muscle weakness, but difficulty performing complex motor tasks
Impair motor response to visual or other sensory cues
Damage to 1 side –> minimal as contralateral side can take over
Posterior parietal cortex
Areas 7 and 19
Damage can lead to sensory apraxia –> difficulty performing complex motor tasks when triggered by sensory input
More a difficulty in linking a sensory input to the motor system
Damage to Broca’s area
Motor aphasia
Difficulty generating speech motor outputs
Difficulty linking word strings into complex sentences
–> can’t construct meaningful word sequences
Damage to Frontal Eye Fields
Oculomotor Apraxia (OMA)
Difficulty moving eyes horizontally + moving them quickly to follow moving object
Patient have to turn head to compensate
Interferes with motor programmes controlling voluntary eye movements
Can appear to have perception problems, but acc just have difficulty with eye movement motor programmes
Sensory apraxia
Damage to connections from posterior parietal lobe to premotor cortex
40% of Corticobulbospinal tract axons arise from..
Anterior parietal lobe (somatosensory cortex), which lies immediately posterior to central sulcus
- -> axons command down to spinal cord that modulate sensory input
- -> modulate reflexes
Dorsolateral prefrontal cortex
Areas 9 and 10
Planning of movement
Evaluate future actions
Problem solving and judgement
Dorsolateral prefrontal cortex lesions
Apathy
Personality changes
Lack of ability to plan or to sequence actions or tasks
Left hemisphere damage- poor working memory for verbal information
Right hemisphere damage- poor working memory for spatial information
Wisconsin Card Sorting test
Test for frontal lobe function
Orbitofrontal cortex
Area 11
Control (inhibition) of motor responses with limbic system
Responses to hunger, thirst, sexual drive
Orbitofrontal cortex damage
Pseudopsycopathic behaviour- impulsiveness, puerility, jocular attitude, sexual disinhibition, complete lack of concern for others
Motor thalamus
VL + VA thalamic nuclei
Only route for motor commands from basal ganglia + cerebellum to be fed into corticospinal tract
Basal ganglia + cerebellum project to motor thalamus –> motor cortex
Corticobulbospinal tract
Passes through internal capsule on way to brainstem
Vulnerable to stroke in this area
Corticobulbar tract- terminates on which cranial nerve nuclei
V + VII for cortical control of muscles of head
Oculomotor nuclei (III, IV + VI) for control of eye movements
Cells on pontine nuclei
Reticular formation
Red nucleus
Red nucleus
Large round nucleus in midbrain next to oculomotor nuclei
Corticospinal tract
Decussates in medullary spinal junction- to opposite side
Forms lateral corticospinal tract and small medial corticospinal tract
Motor decussation
Upper spinal cord C1-5
If brain injured above spinal cord/medulla junction, motor deficit on other side
If spinal cord injured, motor deficit on same side
