Motor cortical control Flashcards
What is hierarchal organisation in motor control?
Higher order areas plan out when to do tasks and coordinate multiple muscles, lower order only execute tasks
What is functional segregation in motor control?
Specific areas of motor system carry out specific tasks
What are the two major descending tracts?
Pyramidal and Extrapyramidal
Give examples for the two tracts
Pyramidal - corticospinal and corticobulbar
Extrapyramidal - vestibulospinal, reticulospinal, tectospinal, rubrospinal
What parts of the brain do the tracts connect?
Pyramidal - motor cortex to spinal cord OR cranial nerve nuclei in the brainstem
Extrapyramidal - brainstem nuclei to spinal cord
What movements do pyramidal/extrapyramidal supply?
Pyramidal - voluntary movements to the body/face
Extrapyramidal - involuntary movements for balance, posture and locomotion
Why are they named pyramidal tracts?
Pass through the pyramids of the medulla
(except) the extrapyramidal tracts
Primary motor cortex
- precentral gyrus (anterior to central sulcus)
- fine, discrete, voluntary movements
- provides descending signals to execute movement
Premotor area
- anterior to primary motor cortex
- involved in planning movements
- reg externally cued movements (how we interact with our environment)
Supplementary motor area
- anterior and medial to primary motor cortex
- involved in planning complex movement (internally cued e.g. speech)
- active prior to voluntary movement
Corticospinal tract
pathway of UMN to LMN
UMN in primary motor cortex, go through white matter through the cerebral peduncle. Reach the medulla and decussate (cross to the other side, this is why lesions affect the contralateral side)
Lateral corticospinal tract
85-90% crossed fibres (post decussation)
limb muscles
Anterior corticospinal tract
10-15% uncrossed fibres
trunk muscles
Motor homunculus
How much brain devoted to a specific part of the body
majority in the hands, then thee tongue/feet
Somatotopic representation
Shows the area of the motor cortex responsible for each part of the body
Explain the function of the corticobulbar tract
Cranial nerves - voluntary movements of eyes, face, jaw, neck and tongue
Explain the function of the vestibulospinal tract
Stabilise head during body movements
coordinate head and eye movements
balance and posture
Explain the function of the reticulospinal tract and where it comes from
postural stability
From medulla and pons, changes in muscle tone in voluntary movement
Explain the function of the tectospinal tract and where it comes from
From superior colliculus of midbrain,
coordinate head and neck movements during eye movements
Explain the function of the rubrospinal tract and where it comes from
innervate LMN of upper limb flexors
From red (rubro) nucleus of midbrain,
What are the 3 negative signs of upper motor neuron lesions? LPP
Loss, of voluntary motor function,
Paresis (graded weakness of movements),
Paralysis/plegia (complete loss of movement)
What are the 5 positive signs of upper motor neuron lesions?
Increased abnormal motor function (loss of inhibitory descending input)
Spasticity (increased muscle tone) - stiff //
Hyperreflexia //
Clonus (oscillatory contraction) //
Babinski’s sign, toes flex backwards
What is apraxia?
Disorder of skilled movement - lost information about how to perform skilled movements
Lesions to which lobes cause apraxia?
Inferior parietal lobe,
frontal lobe (including supplementary motor area and premotor cortex)
What are the 5 signs of a lower motor neuron lesion?
Weakness,
hypotonia, loose muscles
hyporeflexia,
muscle atrophy,
fasciculations,
fibrillations
Fasciculations
Damaged motor units produce spontaneous action potentials which result in a visible twitch
Fibrillations
Spontaneous twitching of individual muscle fibres
Require electromyography to see
What is motor neuron disease and what is its other name?
Progressive neurodegenerative disorder, of the motor tract which involves loss of both UMN and LMN.
ALS - Amyotrophic Lateral Sclerosis
What are the upper motor neuron signs of MND?
Dysarthria (trouble speaking),
Dysphagia
spasticity
babinski’s sign
loss of dexterity
What are the lower motor neuron signs of MND?
Nasal speech,
dysphagia,
tongue wasting
weakness
muscle atrophy
Give examples of 5 basal ganglia nuclei we need to be aware of, and 2 structures pairs of them form
Caudate nucleus,
Putamen,
External Globus Pallidus,
Substantia Nigra,
Subthalmic Nucleus
> > C+P are the striatum // P + EGP is lentiform nucleus
What is the function of the basal ganglia?
Slight changes in movement - decision to move, changing facial expression for emotion, suppressing unwanted movements
Which neurons does Parkinson’s disease affect?
Degeneration of dopaminergic neurons originating in substantia nigra projecting to striatum
What are the 5 signs of Parkinson’s disease?
(think: parKINsons)
Bradykinesia, slowness
Hypomimic face (expressionless),
Akinesia (difficulty in initiating movements),
rigidity, increased muscle tone
tremor at rest, starts in one hand
(think: parKINsons - aKINesia, bradyKINesia)
Which neurons does Huntington’s disease affect?
GABAergic neurons in striatum - caudate and putamen
What are the 6 signs of Huntington’s disease?
Choreic movements (jerky involuntary),
Speech impairment, dysarthria
dysphagia,
unsteady gait,
cognitive decline,
dementia
What is Huntington’s disease
Genetic neurodegenerative disorder
chromosome 4, autosomal dom
due to CAG repeat
What neurons does Ballism affect?
Subthalamic neurons (from stroke)
What are is the main symptom of ballism?
(ballistic)
Sudden uncontrolled flinging of contralateral extremities
Cerebellum
coordinator and predictor of movement
What separates the cerebellum from the cerebrum
tentorium cerebelli
What does the vestibulocerebellum do?
balance, posture, head and eye movement coordination
region in the middle (axial plane) of the cerebellum
What can damage to the vestibulocerebellum arise from and what are its presentations?
Tumour,
gait ataxia & tendency to fall (even when sitting and eyes open)
What does the spinocerebellum do?
Motor execution
medial region of the cerebellum
What can damage to the spinocerebellum arise from and what are its presentations?
degeneration and atrophy from chronic alcoholism,
causes wide based stance and gait (think drunk ppl struggle to stand straight)
What does the cerebrocerebellum do?
(think frontal cortex - CALM)
Motor planning and cognitive fct
What does damage to the cerebrocerebellum do?
Tremor and difficulty in speech
What are the 5 main signs of cerebellar dysfunction?
ataxia (drunken gait),
dysmetria (inappropriate force),
intention tremor
dysdiadochokinesia (cannot perform rapidly alternating movements),
scanning speech (staccato)
