Motor Control Flashcards by Elizabeth Akeju

Outline the broad principles of motor control

Hierarchical organisation
- higher order areas - involved in more complex tasks, e.g. planning movement
- lower order areas - involved in lower level tasks, e.g. execution of movement

Functional segregation
- Different areas control different aspects of movement

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What are the pyramidal tracts?

Corticospinal
Corticobulbar
- Pass through pyramids of the medulla

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What are the extrapyramidal tracts?

Vestibulospinal
Tectospinal
Reticulospinal
Rubrospinal
- Do not pass through pyramids of the medulla

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Outline the route of the pyramidal tracts and their function

Motor cortex to spinal cord or cranial nerve nuclei in brainstem
Voluntary movements of body and face

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Outline the route of the extrapyramidal tracts and their function

Brainstem nuclei to spinal cord
Involuntary (automatic) movements for balance, posture and locomotion

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Where is the primary motor cortex and what is its function?

Precentral gyrus
Controls fine, discrete, precise voluntary movements
Provides descending signals to execute movements

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Where is the premotor area and what is its function?

Anterior to primary motor cortex
Involved in planning movements
Regulates externally cued movements, e.g. seeing an apple and reaching for it

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Where is the supplementary motor area and what is its function?

Located anterior and medial to primary motor cortex
Involved in planning complex movements (e.g. internally cued, speech)
Becomes active prior to voluntary movement

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Describe the route of the corticospinal tract

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Outline the somatotopic representation of the motor and sensory cortices

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What is the function of the corticobulbar tract?

Principal motor pathway for voluntary movements of the face (and neck)

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What is the function of the vestibulospinal tract?

Stabilise head during body movements, or as head moves
Coordinate head movements with eye movements
Mediate postural adjustments

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What is the function of the reticulospinal tract?

Most primitive descending tract - from medulla and pons
Changes in muscles tone associated with voluntary movement
Postural stability

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What is the function of the tectospinal tract?

From superior colliculus of midbrain
Orientation of the head and neck during eye movements

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What is the function of 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

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What are the negative sign(s) of upper motor neuron lesion?

Loss of voluntary motor function

What is the different between ‘paresis’ and ‘plegia’?

Paresis: graded weakness of movements
Paralysis (plegia): complete loss of voluntary muscle activity

What are the positive signs of upper motor neuron lesion?

Increased abnormal motor function due to loss of inhibitory descending inputs
Spasticity: increased muscle tone
Hyper-reflexia: exaggerated reflexes
Clonus (twitching/jerking): abnormal oscillatory muscle contraction
Babinski’s sign

What is apraxia?

A disorder of skilled movement. Patients are not paretic (don’t have paresis) but have lost information about how to perform skilled movements

What can cause apraxia?

Lesion of inferior parietal lobe
Lesion of the frontal lobe (premotor cortex, supplementary motor area - SMA)
Most common - stroke and dementia

What are the characteristics of a lower motor neuron 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 neuron disease?

Progressive neurodegenerative disorder of the motor system
Spectrum of disorders - upper and lower motor neuron symptoms
Also known as Amyotrophic Lateral Sclerosis (ALS)

What are the upper motor neuron signs of motor neuron disease?

Spasticity (increased tone of limbs and tongue)
Brisk limbs and jaw reflexes
Babinski’s sign
Loss of dexterity
Dysarthria (difficulty speaking)
Dysphagia (difficulty swallowing)

What are the lower motor neuron signs of motor neuron disease?

Weakness
Muscle wasting
Tongue fasciculations and wasting
Nasal speech
Dysphagia

What structures make up the basal ganglia?

Caudate nucleus Lentiform nucleus (putamen + external globus pallidus) – together caudate and putamen are known as the striatum Nucleus accumbens Subthalamic nuclei Substantia nigra (midbrain) Ventral pallidum, claustrum, nucleus basalis (of Meynert)

What are the functions of the basal ganglia?

- Decision to move - Elaborating associated movements (e.g. swinging arms when walking; changing facial expression to match emotions - Moderating and coordinating movement (suppressing unwanted movements) - Performing movements in order Helps us perform fluid movements

What is Parkinson’s Disease?

A condition caused by the degeneration of the dopaminergic neurons that originate in the substantia nigra and project to the striatum

What are the symptoms of Parkinson’s Disease?

Bradykinesia - slowness of (small) movements (doing up buttons, handling a knife) Hypomimic face - expressionless, mask-like (absence of movements that normally animate the face) Akinesia - difficulty in the initiation of movements because cannot initiate movements internally Rigidity - muscle tone increase, causing resistance to externally imposed joint movements Tremor at rest - 4-7 Hz, starts in one hand (“pill-rolling tremor”); with time spreads to other parts of the body

What is Huntington’s Disease?

Condition caused by degeneration of GABAergic neurons in the striatum, caudate and then putamen

What are the symptoms of Huntington’s Disease?

Choreic movements (chorea - dance) - rapid jerky involuntary movements of the body; hands and face affected first; then legs and rest of body Speech impairment Difficulty swallowing Unsteady gait Later stages, cognitive decline and dementia

What causes Huntington’s Disease?

Genetic neurodegenerative disorder Chromosome 4 Autosomal dominant CAG repeat

What is ballism and what is it usually caused by?

Sudden uncontrolled flinging of the extremities Usually from stroke affecting the subthalamic nucleus Symptoms occur contralaterally

Where is the cerebellum and what is its function?

Located in posterior cranial fossa Separated from cerebrum above by tentorium cerebelli Coordinator and predictor of movement - compares what is happening with what should be happening and makes fine adjustments

What is the function of the vestibulocerebellum?

Regulation of gait, posture and equilibrium Coordination of head movements with eye movements

What happens when the vestibulocerebellum is damaged?

Damage usually due to a tumour Causes a syndrome similar to vestibular disease leading to gait ataxia and tendency to fall (even when patient is sitting and eyes open)

What is the function of the spinocerebellum?

Coordination of speech Adjustment of muscle tone Coordination of limb movements

What happens when the spinocerebellum is damaged?

Damage usually due to degeneration and atrophy associated with chronic alcoholism Affects mainly legs - causes abnormal gait and stance (wide-based)

What is the function of the cerebrocerebellum?

Coordination of skilled movements Cognitive function, attention, processing of language Emotional control

What are the main signs of cerebellar dysfunction?

Ataxia: General impairments in movement coordination and accuracy. Disturbances of posture or gait: wide-based, staggering (“drunken”) gait Dysmetria: Inappropriate force and distance for target-directed movements (knocking over a cup rather than grabbing it) Intention tremor: Increasingly oscillatory trajectory of a limb in a target-directed movement (nose-finger tracking) Dysdiadochokinesia: Inability to perform rapidly alternating movements (rapidly pronating and supinating hands and forearms) Scanning speech: Staccato, due to impaired coordination of speech muscles