Motor cortical control Flashcards
what are the pyramidal tracts?
corticospinal and corticobulbar
they pass through the pyramids of the medulla
what are the extrapyramidal tracts?
vestibulospinal tectospinal reticulospinal rubrospinal not pass through the pyramids of the medulla
what does the primary motor cortex do?
control fine, discrete, precise voluntary movement
descending signals to execute movements
what does the premotor area do and where is it?
-> anterior of the primary motor cortex
planning movements
regulate externally cued movements
what does the supplementary motor area do and where is it?
anterior and medial to the primary motor cortex
involved in planning complex movements
describe the corticospinal
Lower motor neurone -> 85-90% of the fibres cross lateral corticospinal tract supplying the limbs -> decussation of the pyramids
the anterior which is the rest continue, and not decussate -> continue in medulla, midbrain and cerebral peduncle at the upper motor neurone in the motor cortex
these are the trunk muscls
What is the corticobulbar tract?
primary motor pathway for the voluntary movements of the face and the neck
describe the path of the corticobulbar pathway?
basal ganglia (precentral gyrus, caudate nucleus, putamen, globus pallidus, thalamus)
nerves-> ocuolomotr
trochlear, trigeminal, abducens, facial and hypoglossal nuclei
What is the vestibulospinal tract?
Stabilise head during body movements, or as head moves
Coordinate head movements with eye movements
Mediate postural adjustments
What is the reticulospinal tract?
Most primitive descending tract - from medulla and pons
Changes in muscles tone associated with voluntary movement
Postural stability
What is the tectospinal tract?
From superior colliculus of midbrain
Orientation of the head and neck during eye movements
What is the rubrospinal tract?
From red nucleus of midbrain
In humans mainly taken over by corticospinal tract
Innervate lower motor neurons of flexors of the upper limb
Negative signs of UM lesion ?
Loss of voluntary motor function
Paresis: graded weakness of movements
Paralysis (plegia): complete loss of voluntary muscle activity
Positive signs of UM lesions?
Increased abnormal motor function due to loss of inhibitory descending inputs
Spasticity: increased muscle tone
Hyper-reflexia: exaggerated reflexes
Clonus: abnormal oscillatory muscle contraction
Babinski’s sign
What is apraxia?
Disorders of skilled movements
lesion of inferior parietal lobe, and frontal lobe (all motor regions)
Common causes of apraxia?
Dementia and stroke
Symptoms of LM lesion?
Weakness
Hypotonia (reduced muscle tone)
Hyporeflexia (reduced reflexes)
Muscle atrophy
Fasciculations: damaged motor units produce spontaneous action potentials, resulting in a visible twitch
Fibrillations: spontaneous twitching of individual muscle fibres; recorded during needle electromyography examination
What is motor neurone disease?
Progressive neurodegenerative disorder of the motor system. Spectrum of disorders
What is motor neurone disease also known as?
amyotrophic lateral sclerosis ALS
UM signs of MND?
Spasticity (increased tone of limbs and tongue)
Brisk limbs and jaw reflexes
Babinski’s sign
Loss of dexterity
Dysarthria (difficulty speaking)
Dysphagia (difficulty swallowing)
LM signs of MND?
Weakness
Muscle wasting
Tongue fasciculations and wasting
Nasal speech
Dysphagia
Basic structures of the basal ganglia?
Caudate nucleus Lentiform nucleus ( which is made up of the putamen and the external globus pallidus)
Caudate and putamen make up the striatum
Nucleus accumbens
Subthalamic nuclei
Substantia nigra
Ventral pallidum, claustrum and nucleus basalis (of Meynert)
LOOK AT PICTURE
What is the function of the basal ganglia?
Decision to move
Elaborated associated movements -> eg swinging arms when walking
moderating and coordinating movements (supressing unwanted movements)
Performing movements in order
What is Parkinson’s disease?
Degeneration of the dopaminergic neurons that originate in the substantia nigra and project to the striatum
Symptoms of parkinson’s
Bradykinesia Hypomimic face Akinesia Rigidity Tremor at rest -> 4-7Hz
What is Huntingtons disease?
Degeneration of GABAergic neurons in the striatum, caudate and then putamen
What kind of disorder it Huntington’s disease?
Genetic -> neurodegenerative
chromosome 4 autosomal
CAG repeat
Symptoms of Huntington’s disease?
Choreic movements -> rapid jerky, dance like movements, hands and face affected first and then legs and rest of body
Speech impairment
Difficulty swallowing
Unsteady gait
Later stages, cognitive decline and dementia
What is ballism and what causes it?
stroke affecting the subthalamic nucleus
flinging of extremities
symptoms occur contralaterally
What does the cerebellum do?
coordinator and predictor of movement
what is the vestibulocerebellum?
Regulation of gait, posture and equilibrium
Coordination of head movements with eye movements
Condition with vestibulocerebellum?
Damage (tumour) causes syndrome similar to vestibular disease leading to gait ataxia and tendency to fall (even when patient sitting and eyes open)
What does the spinocerebellum do?
Coordination of speech
Adjustment of muscle tone
Coordination of limb movements
What is the condition of the spinocerebellum?
Damage (degeneration and atrophy associated with chronic alcoholism) affects mainly legs, causes abnormal gait and stance (wide-based)
What does the cerebrocerebellum do?
Coordination of skilled movements
Cognitive function, attention,
processing of language
Emotional control
Condition of cerebrocerebellum?
Damage affect arms/skilled coordinated movements (tremor ) and speech
Main signs on cerebellar dysfunction?
ataxia
dysmetria
intention tremor
dysdiadochokinesia -> not able to perform rapidly continuing movements
Scanning speech -> staccato due to impaired coordination of speech muscles
