Motor Systems II Flashcards
Which lobe is involved in motor control?
Frontal lobe
The more anterior or posterior the cortical region, the more complex the movement is?
anterior
Which area is primary motor cortex?
4
Where is area 4 (primary motor cortex) found?
Immediately anterior ro central sulcus
What is the lowest level of motor ‘hierarchy’?
Primary motor cortex
Local lesions cause what?
paralysis of specific muscle groups
Define neuronal plasticity
motor homunculus map changing to resolve small lesions
What happens if a stroke occludes the MCA?
Affect a whole side of the frontal lobe, producing contralateral defects
How many parts are there of the MCA and name them
M1, M2 and M3
Which is the worst blockage in in MCA?
M1 is worse than M3 as M1 supplies the basal ganglia while M3 doesn’t
What area is the premotor?
6
What area is the supplementary motor?
8
What will happen if there is damage to area 6+8?
apraxia - loss of ability to plan and carry out complex movements
What will not happen with damage to areas 6+8?
No paralysis
No reflex loss or muscle weakness
Which area is Broca’s area?
44 + 45
What does area 44 + 45 regulate?
speech muscles
Damage to area 44 + 45 causes what?
motor aphasia so cannot string together complex sentences
What area is are the Frontal Eye Fields in?
8
What do the Frontal Eye Fields regulate?
Extraocular eye muscles
What happens if there is damage to the Frontal Eye Fields?
oculomotor apraxia
difficulty moving eyes horizontally and moving them quickly to follow an object
What will patients do to compensate for a symptom in damage to frontal eye fields?
Turn their head
What is the main cause of damage to FEF?
Bilateral lesion
What areas is the Dorsolateral Prefrontal Cortex located in?
Areas 9 + 10
What is the dorsolateral prefrontal cortex related to?
Movement
Evaluation of different possible future actions
Problem solving + judgement
What does dorsolateral frontal lesions cause?
apathy
personality changes
lack of ability to perform actions or tasks
What happens with left hemisphere damage?
Poor working memory for verbal information
What happens with right hemisphere damage?
Poor memory for spatial information
Where is the orbitofrontal cortex located?
Area 11
What does the orbitofrontal cortex control?
motor responses associated with limbic system
How does orbitofrontal cortex control motor responses with the limbic system?
Through inhibition
What does orbital damage lead to?
disinhibition which leads to ‘pseudo-psychopathic behaviour’ e.g. impulsiveness and complete lack of concern for others
Define orbital personalities
Acquired sociopathy or pseudo=psychopathic behaviour
40% of corticobulbospinal tracts arise from where?
Somatosensory cortex (areas 3, 1 and 2)
Which aspect of the thalamus is responsible for motor control?
Ventral lateral
Why is ventral lateral aspect of thalamus important?
Used for motor commands from basal ganglia and cerebellum to be fed into corticospinal tract
Stroke damage to VL thalamus causes what?
Severe paralysis
What are the two parts to the pyramidal tracts?
Corticospinal and corticobulbar
How does the pyramidal tracts get to the brainstem?
Through the internal capsule
Where does motor decussation occur for pyramidal tracts?
Upper spinal cord
Where does the Corticobulbar tract terminate?
Brainstem on cranial nerves
Which nucleui control muscles of head + neck?
CN nuclei
What does CN nuclei also control?
pontine nuclei, reticular formation (consciousness) and red nucleus (motor coordination)
Where does corticospinal tract terminate?
Spinal cord
Where does corticospinal tract decussate?
Medullary pyramids and upper spinal cord (C1-C5), so UMN lesion causes contralateral damage
What does corticospinal tract split into?
Large lateral corticospinal tract
Small anterior corticospinal tract
Where does the lateral corticospinal tract run?
Dorsolateral cord
Where does anterior corticospinal tract run?
Medial ventral cord
Which quadrant is the lateral corticospinal tract located in?
Dorsal quadrant of the cord
Where is the Corticospinal tract near?
Motor neurones supplying distal muscles
What does the anterior CST tract control?
Voluntary movement of the neck
Where is the anterior CST tract only present?
Cervical cord
What does the lateral CST supply?
Distal muscles
What are all other muscles supply by the CST mediated by?
Actions of spinal interneurones
What causes inhibition of flexion reflexes?
Modulated by CST
What happens if there is damage to CST tract in spinal cord?
Loss of control of hands and digits BUT NOT LOSS OF POSTURE OR LOCOMOTION OR GAIT
What tract mediates posture locomotion and gait
Extrapyramidal system
Where does the extrapyramidal system originate?
Brainstem
What are the main components of extrapyramidal system?
Vestibulospinal + Reticulospinal tracts
Where does the lateral vestibulospinal tract originate?
Vestibular nucleo of upper medulla/ lower pons
How does the vestibulospinal tract project?
Ipsilaterally to antigravity muscles
What does the vestibulospinal tract control?
Posture and balance
When is the lateral vestibulospinal tract tonically active?
During upright position
Where does the reticulospinal tract arise?
Reticular formation of pons and medulla
How does reticulospinal tract project?
Bilaterally down the spinal cord
What is the reticulospinal tract responsible for?
Autonomic control (temperature/BP) and drive for respiration
Where does rubrospinal tract originate?
Red nucleus of brainstem
Where does red nucleus receive main input from?
Cerebellum
What does rubrospinal tract carry out?
Cerebellar commands to the spinal cord
What is red nucleus
Large nucleus in the midbrain
What does tectospinal tract do?
Coordinates voluntary head and eye movement
Where does tectospinal tract originate?
Superior colliculus
Where does tectospinal tract project to?
Cervical spinal cord
Where does tectospinal tract terminate?
Rexed laminae vi, VII and VIII
What does tectospinal tract do?
Mediates movements of the head in response to visual and auditory stimuli
What is spasticity?
Abnormally increased muscle tone
What is increased in spastic muscles?
Tendon reflexes
What is spasticity a characteristic of?
UMN damage causing excessive muscle contraction
What is clonus
Series of jerky contractions of a certain muscle following stretching of said muscle
What is hyperreflexia?
Over reactive or overresponsive reflexes
What does decorticate posturing indicate?
damage to CST in midbrain
What is decorticate posturing?
Arms adducted and flexed
Wrists and fingers flexed on chest
Legs internally rotated and stiffly extended
Plantar flexion of feet
What does Decerebrate posturing indicate?
Severe injury to brain in brainstem affecting CST and rubrospinal tracts
What causes decerebrate posturing?
Excessive activity (disinhibition) in extrapyramidal system
Which tract is particularly affected in decerebrate posturing?
Vestibulospnial tract
Decerebrate posturing is usually inhibited by what?
CST tract and red nucleus
What occurs in decerebrate posturing
Arms adducted and extended
Wrists pronated and fingers flexed by the side
Legs internally rotated and stiffly extended
Planter flexion of feet
What does Acute Motor Cortex lesion lead to?
Initial paralysis
What is there during recovery of acute motor cortex lesion?
Weakness
Clumsiness
Fatigue
Why does recovery occur in acute motor cortex lesion?
Plasticity in cortex homunculus is changed
What will always be present in chronic motor cortex lesion?
Motor weakness and fatigue
What shows profound motor weakness in chronic motor cortex lesion?
If spasticity remains
What is a classic characteristic of chronic cerebral motor lesions
Clasp-knife reflex
Why does clasp knife occur?
Due to massive drop in resistance when attempting to flex a joint
What is hemiplegic dystonia
Persistent flexion of arms and extension of legs
Why does spinal shock occur
Occurs after damage to spinal cord (and descending tracts)
What occurs in spinal shock?
Paralysis and reduced reflex response in all muscles below site of injury
How long does spinal shock last for?
Days or months depending on severity
What will reappear overtime in spinal shock?
Monosynaptic reflexes
What may be present in spinal shock?
Clonus or babinski sign
