Motor systems 2 Flashcards
The more anterior the structure…
The more abstract its role in movement
What is area 4 of the brain called
Primary motor cortex
What is the result of a lesion in the primary motor cortex
Paralysis of muscle groups
Result of medial lesion to primary motor cortex
Loss of leg function
Result of lateral lesion to primary motor cortex
Loss of arm function
What is area 6 called
Premotor cortex
What is area 8 called
Supplementory motor cortex
What happens if there is damage to areas 6/8
Apraxia
What is apraxia
Reflexes and muscle strength normal, but there is a difficult in performing complex motor tasks
What is ideational apraxia
Unable to plan motor tasks so can’t carry out multistep tasks– can’t explain how one would do that task
What is ideomotor apraxia
Unable to complete tasks that rely on semantic memory but can explain how to do it
What are areas 9/10 called
Dorsolateral prefrontal cortex
What is the role of areas 9/1-
Planning of movements Executive function (problem solving a judging)
What does it suggest if extra perseverance is seen when patient does the Winconsin card sorting test
Lesion to areas 9/10
What happens if there is bilateral damage to frontal eye fields
Oculomotor apraxia
What is oculomotor apraxia
Unable to follow objects
Absence of fast phase nystagmus
People move head instead of eyes
What is area 11 called
Orbitofrontal cortex
What is the function of area 11
Control/ inhibition of motor function associated with limbic system
What are areas 1,2,3 called
Somantosensory cortex
What % of the corticobulbar tract arises from somatosensory cortex
40
Role of somatosensory cortex in movement
Modulate sensory input and reflexes
What are the motor symptoms of strokes involving occlusion of MCA
Produce severe motor disability in all parts of contralateral body apart from lower limb (this is supplied by anterior cerebral artery)
As well as the motor cortex, what other important structure does MCA stroke affect
Blood supply to basal ganglia via lenticulostriate arteries
What structure in an important route for motor commands from the basal ganglia and the cerebellum into corticospinal tract
Motor thalamus (VL thalamic nucleus)
Result of stroke damage to motor thalamus?
Severe paralysis
What structure does the corticobulbospinal tract course through
Internal capsule
Where does the corticobulbar component of the corticobulbospinal tract terminate
Various cranial nerve nuclei
Pontine nuclei
Reticular formation
Red nucleus
Where is the red nucleus found
In the midbrain next to oculomotor nuclei
Where does the corticospinal component of tract cross
Lower medulla
What does the corticospinal tract form once its decussated
Large lateral tract
Small medial tract
Where does motor decussation happen
Upper spinal cord and lowest part of medulla
Where does sensory decussation happen
Rostral medulla
If the brain is injured above the spinal cord is the motor deficit on the same or opposite side
Opposite
If the spinal cord is injured is motor deficit on same or opposite side
Same
Where does the lateral corticospinal tract run
In the dorsolateral cord
Where does the anterior corticospinal tract run
In the medial ventral cord
What does the corticospinal tract have monosynaptic connections with
Motor neurones of thumb and digits
How does the corticospinal tract initiate movements in muscles it doesn’t synapse directly onto
Via spinal interneurones
Where does the anterior/ ventral corticospinal tract terminate
Cervical cord
What does the cervical cord control
Voluntary movement of neck and shoulder
Damage to the corticospinal tract in the spinal cord causes what
Loss of control of hands and fingers
What other motor system mediates motor functions of posture locomotion and gait
Extrapyramidal system
Name 3 major extrapyramidal tracts
Lateral vestibulospinal tract
Reticulospinal tract
Rubrospinal tract
Where does the lateral vestibulospinal tract originate
Vestibular nuclei in upper medulla/ lower pons
What is the function of the lateral vestibulospinal tract
- Posture and balance
- Nucleus projects ipsilaterally to antigravity muscles
- Tonically active when upright
Where does the reticulospinal tract arise from
Reticular formation of pons and medulla
What is the function of the reticulospinal tract
Autonomic conrtol
Drive to respiration
General arousal of spinal cord
What is the function of the rubrospinal tract
Carries cerebellar commands to spinal cord
Where does the rubrospinal tract arise from
Red nucleus in the brainstem
What 2 things does the red nucleus give rise to
Rubrospinal tract
Large ascending projection to motor thalamus
Name 2 minor extrapyramidal tracts
Tectospinal tract
Medial vestibulospinal tract
What is the function of the tectospinal tract
Coordinates voluntary head and eye movements in response to visual/ auditory stimuli
Where does the tectospinal tract originate from
Superior colliculus
Where does the superior colliculus project to
Contralateral cervical spinal cord
Where does tectospinal tract terminate
rexed laminae VI, VII and VIII
What is the medial vestibulospinal tract a continuation of
Medial longitudinal fasciculus
Function of the medial vestibulospinal tract
Mediates coordination of head and neck muscles with extraocular eye muscles to maintain objects in view despite body movement
Define spasticity
Abnormally increased muscle tone
What is spasticity characteristic of
Upper motorneurone lesions
What is clonus
Series of jerky contractions following sudden stretching of the muscles
What is hyperreflexia
Abnormally/ pathologically brisk tendon reflex seen in one or more muscle
What does decorticate posturing indicate
Damage to corticospinal tract in midbrain
What does decerebrate posturing indicate
Damage at level of brainstem including damage to corticospinal and rubrospinal tracts
Describe decorticate posturing
Arms adducted and flexed
Wrists and fingers flexed on chest
Legs may be internally rotated and stiffly extended
Plantar flexion of feet
Describe decerebrate posturing
Arms adducted and extended
Wrists pronated and fingers flexed
Legs internally rotated and stiffly extended
Plantar flexion of feet
Is decorticate or decerebrate posturing favourable
Decorticate
Explain the mechanism thought to underly decerebrate posturing
- Excessive activity (disinhibtion) of extrapyramidal system esp vestibulospinal tract
- Vestibulospinal tract usually under tonic inhibition by corticobulbospinal tract and red nucleus
- If red nucleus damaged may lead to this posture
How can recovery occur after lesions to motor cortex
Because of plasticity
After a lesion to face area, face cells may be driven by cells from different part of cortex and homonculus is changed
What is hemiplegic dystonia
Persistent flexion of arms and extension of legs following lesion to motor cortex
What reflex is characterised of chronic cerebral motor lesions
Clasp knife
What is spinal shock
Clinical condition occuring after acute damage to spinal cord including damage to descending tracts
What is the acute effect of spinal shock
Paralysis/ paresis
Reduced reflex response in all muscles below injury
What are the chronic effects of spinal shock
Weak monosynaptic reflexes
Crossed extensor reflexes may recover
May be exaggerated and hyerpactive
Babinski sign present
What symptoms of spinal injury can be attributed to reticulospinal tract (4)
Loss of bladder/ bowel control
Poor gait, loss of walking
Loss of temp regulation
Loss of BP regulation
What symptoms of spinal injury can be attributed to corticospinal tract
Paralysis/ weakness voluntary movement
Hyperactive tendon reflexes
What symptoms of spinal injury can be attributed to vestibulospinal tract
Loss of ability to stand/ balance
Poor gait, loss of ability to walk
Common causes of upper motor neuron lesion
CVA, trauma, MS, ALS
Common cause of lower motor neuron lesion
CVA, polio, tumour, alcoholism, diabetes
What structures are involved in UMN lesion?
What is the distribution?
MOtor cortex/ corticospinal tract/ other tracts
Never just individual muscle, always groups
What structures are involved in LMN lesion?
What is distribution?
Spinal or brainstem a-motor neurones or peripheral motor aons
Limited to muscle innervated by damaged motorneurones
What is the effect of UMN lesion on voluntary movement
Parlysis or paresis
What is the effect of LMN lesion on voluntary movement
Paralysis
What is the effect of UMN lesion on muscle tone
Increased
What is the effect of LMN lesion on muscle tone
Decreased
What is the effect of UMN lesion of reflexes
Myotactic reflexes will be hyperactive
Some cutaneous reflex abnormalities (babinkski)
What is the effect of LMN lesion on reflexes
Decreased or absent
What is the classical description of UMN lesion and LMN lesion
UMN= spastic paralysis LMN= flaccid paralysis
