Motor Control Flashcards
What is hierarchical organisation?
Higher orders do higher level of tasks which are more complicated and lower orders do lower tasks
What is functional segregation?
Motor system organised in a number of different areas that control different conckecst of movement
What are the pyramidal tracts and why are they called pyramidal tracts?
Pass through the pyramids of the medulla
- Corticospinal
- Corticobulbar
Go from motor cortex to the spinal cord or cranial nerve nuclei in brainstem
What are the Extrapyramindal tracts?
Do not pass through the pyramids of medulla
- Vestibulospinal
- Tectospinal
- Reticulospinal
- Rubrospinal
Brainstem nuclei to spinal cord
What does the primary motor cortex control?
Controls fine, discrete, precise voluntary movements
Descending signals to execute movements
What are premotor area control?
Involved in planning movements
Externally cued movement e.g. seeing and apple and reaching for it
What does the supplementary motor area do?
Planning complex movements which are internally cued e.g. speech
- becomes active prior to voluntary movement
What percentage of fibres from corticospinal tract is responsible for trunk muscles?
10-15% uncrossed fibres = anterior corticospinal tract
What do the motor nerves from the corticobulbar tract do?
Synapse with brainstem cranial nerve nuclei
What is the corticobulbar tract responsible for?
principle motor pathway for voluntary movements of face + neck
What does vestibulospinal tract control?
head movement with eye movement coordination
Stablise head during body movements
postural adjusting
What does reticulospinal tract control?
arises from medulla and pons
changes muscle tone with voluntary movement
+
postural stability
What does the tectospinal tract control?
arises from superior colliculus of midbrain
head and neck orientation during eye movements
What does the rubrospinal tract control?
Arises from red nucleus of midbrain
mainly taken over by corticobulbar tract
Innervate lower motor nuerones of flexors of upper limb
What negative signs are seen with upper motor neuron lesions? (3)
Loss of : voluntary movement
Paresis : graded weakness of movements
Paralysis : complete loss of voluntary muscle activity = plegia
What are the positive signs seen with upper motor nueron tract? (4)
- increased function abnormally Spasticity = increased muscle tone - Hyper-reflexia - Clonus - Babinski's sign
Why is increased motor function seen in upper motor neurone lesions?
Less descending inhibition inputs
What is clonus? Why is this relevent?
Abnormal oscillatory muscle contraction :
seen in upper motor neurone lesions
What is Apraxia?
A consequence of U.M.N.L
disorder of skileld movements
Meaning px will not have paralysis but lost information about how to perform skilled movements
What are common causes of apraxia?
Stroke and dementia
What symptoms and signs are seen in lower motor neurone lesions? (6)
- Weakness
- Hypotonia
- Hyporeflexia
- Muscle atrophy
- Fasciculations
- Fibrillations
Why do fasciculations result in a twitch?
Damaged motor units produce spontaneous APs at NMJ = twitch
What are fibrillations and how can we record these?
Spontaneous twitching of individual muscle fibres
- use needle electromyography examination
What is Motor neuron disease - MND and what is it also known as?
Progessive neurodegenerative disorder of motor system
ALS = amyotrophic lateral sclerosis
Affects both upper and lower neurones
Can cause a spectrum of disorders affecting intercostal muscles, lower and upper limb muscles, tongue
Why can ALS cause death?
Over time it gets worse
- affects respiration due to muscles
What are the UMN signs in ALS/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)
What are the LMN signs in ALS/MND?
- Weakness
- Muscle wasting
- Tongue fasciculations and wasting
- Nasal speech
- Dysphagia
What structures are found in the basal ganglia?
- Caudate nucleus
- Lentiform nucleus ( made of putamen and external pallidus ) *together caudate and putamen are known as striatum
- Nucleus accubens
- Subthalamic nuclei
- Substantia nigra (midbrain)
- ventral pallidum, claustrum, nucleus basalis ( of meynert )
What is the function of the basal ganglia?
Make the decision to move
Elaborating associated movements e.g. swinging arms when walking, changing facial expressions to match emotions
Suppressing unwanted movements
Performing movements in order
What abbreviation is used to remember the parts of the basal ganglia?
C - caudate nucelus P - putamen G - external Globus pallidus T - Thalamus Acc - nucelus accumbens Am - Amygdala Ac - Anterior commisure
Why are there so many complications with the basal ganglia?
A big circulitry with many input and output paths (slide 20)
What is Parkinson’s caused by?
Degeneration of the dopamingergic nuerones that orginate in the substania niagra and project to the striatum
What are the signs and symptoms of parkinsons?
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 Huntingtons disease caused by?
Denegeration of GABAergic neurons in the striatum, caudate and putamen
It is a chromosome 5 authosomal dominent CAG repeat disorder
What are the signs and symptoms of Huntingons 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 is Ballism?
Sudden uncontrolled flinging of the extremties
Symptoms occur contralaterally
What is Ballism caused by?
usually from stroke affecting subthalamic nucelus
Where is the cerebellum located?
Posterior cranial fossa
Sepreated from cerebrum above by tentorium cerebelli
It is the coordinator and predictor of movement
What is the vestibulocerebellum ?
Regulation of gait, posture and equilibrium
Coordination of head movements with eye movements
What does a damage such as tumour affecting the vestibulocerebellum do to the px?
Damage (tumour) causes syndrome similar to vestibular disease leading to gait ataxia and tendency to fall (even when patient sitting and eyes open
What is the spinocerebellum?
Coordination of speech
Adjustment of muscle tone
Coordination of limb movements
What does damage to the spinocerebellum do to a px?
affects mainly legs, causes abnormal gait and stance (wide-based)
Why may the spinocerebellum be damaged?
Degeneration and atrophy associated with chronic alcoholism
What does the cerebrocerebellum do?
Coordination of skilled movements
Cognitive function, attention,
processing of language
Emotional control
What does damage to the cerebroccerebellum do to the px?
affects mainly arms/skilled coordinated movements (tremor) and speech
What are the mains signs of cerebellar dysfunction? (5)
These are apparanet only on movement:
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
