Motor system FINAL Flashcards
Motor control organisation
2 types
1) Functional segregation
2) Hierarchial organisation
1) Functional segregation: Organised in no of different areas that control different aspects of mvmt
2) Hierarchial organisation:
High order areas of hierarchy involved in more complex tasks (programme, coordinate)
Lower level areas- perform lower level tasks (Execution of mvmt)
Function of brain stem in motor organisation
Passes commands from cortex to spinal cord
Function of motor cortex in motor organisation
Receives info from other cortical areas and sends commands to brainstem and thalamus
Which organs adjusts commands received from other parts of motor control
Function of basal ganglia and cerebellum in motor organisation
Location of motor cortex
Function
Precentral gyrus, anterior to central sulcus
Control fine, discrete, precise VOLUNTARY mvmt
Penfield motor hommunculus: where are legs and head
Legs at midline Head lateral
Which artery supplies the medial part of brain
Lateral corticospinal tract:
Legs at midline (this part of brain in supplied by anterior cerebellar artery– stroke in this area=difficulty walking)
1) Betz cell project from primary motor cortex through internal capsule of basal ganglia
2) Pass through midbrain at cerebral peduncle
3) Through pons
4) Into pyramids of medulla, followed by decussation
5) Descend into lateral corticospinal tract
6) At appropriate level project to ventral horn of spinal cord
7) Synapse with alpha motor neuron which leaves through ventral root, out through spinal nerves to musculature
Anterior corticospinal tract
what muscles
CN nuclei located where
Decussate at level of spinal cord
–> largely input to muscles of thorax, axial musculature
in brainstem
Corticobulbar pathway
1) Head region of motor cortex (think of homonculus-lateral) fibres pass through internal capsule of basal ganglia
2) Synapse in brainstem at CN nucleus
3) CN nerve pass out
Premotor cortex located at
Function
Frontal lobe anterior to M1 (Primary motor cortex)
Planning of movement
Regulates externally cued mvments
-Requires awareness of intrapersonal space and extrapersonal space
Supplementary motor area
function
Frontal lobe, anterior to primary motor medially– closer to midline
- Planning complex movements and programming sequences of mvmts
- Regulates internally driven movements
Association cortex
Which areas
Not strictly motor areas,
Why is the association cortex not regarded as a motor area
Which areas
their activity doesn’t correlate with motor output
> Posterior parietal cortex: ensures movements are TARGETED ACCURATELY to objects in external space
Prefrontal cortex: Involved in SELECTION OF APPROPRIATE movements for a particular course of action
Lower motor neurons refers to those in
Upper motor neurons refers to those in
Spinal cord and brainstem
corticospinal, corticolobular
Pyramidal
Lateral cortcospinal tract
Extra-pyramidal
Basal ganglia + Cerebellum – Adjust commands received from other parts of motor control
Upper motor neuron lesions effects
Negative signs: LOSS OF FUNCTION
- Paresis:Graded weakness of movements
- Paralysis: Plegia
Postive signs: INCREASED ABNORMAL MOTOR FUNCTION
-Spasticity: increased muscle tone
-Hyper-reflexia: Exaggerated reflexes
-Clonus: Abnormal oscillatroy muscle contraction
:Babinski sign
Apraxia
Lesions where result in this? what might these be caused by?
Disorder of skilled movements, not paretic but lost information how to perform
Lesions–STROKE+DEMENTIA of inferior parietal lobe, frontal (Premotor cortex, supplementary area)
Lower motor neuron lesion effects
Weakness Muscle wasting Tongue fasciculations and wasting Nasal speech Dysphagia
Motor neuron disease is what?
Example
Progressive neurodegenerative disease of the motor system
ALS
Structures of basal ganglia include
Caudate nucleus
Lentiform nucleus (putamen + external globus pallidus)
Subthalamic nucleus
Substantia nigra
Ventral pallidum, claustrum, nucleus accumbens, nucleus basalis of Meynert
Basal ganglia function
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
Symptoms of Parkinsons
Cognitive decline
Bradykinesia
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 so bilateral
Neuropathology of parkinsons
neurodegeneration of the dopaminergic neurons that originate in the substantia nigra and project to the striatum
Huntingdon’s disease what sort of disorder
Which chromosome
-issue?
Genetic neurodegenerative disorder
Chromosome 4, autosomal dominant
CAG repeat
Degeneration of GABAergic neurons in the striatum, caudate and then putamen
Motor signs of huntingdons
Choreic movements (Chorea)
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
Fold of dura that covers cerebellum
tentorium cerebelli
structure connected to cerebellum
pons
How many layers in cerebellum and names from outer
and contain
Connections
3
Molecular– few neurones
Piriform layer- Purkenje cells project to nuclei in white matter of cerebellum
Granular layer- Small neurones for processing
Inferior olive projects to Purkinje cells via climbing fibres
All other input to granule cells via mossy fibres and then onwards via parallel fibres
All output from Purkinje cells via deep nuclei
Vestibulocerebellum function
Vestibulocerebellar Syndrome
Regulation of gait, posture and equilibrium
Coordination of head movements with eye movements
Damage (tumour) causes syndrome similar to vestibular disease leading to gait ataxia and tendency to fall (even when patient sitting and eyes open)
Spinocerebellum
Spinocerebellar syndrome
Coordination of speech
Adjustment of muscle tone
Coordination of limb movements
Damage (degeneration and atrophy associated with chronic alcoholism) affects mainly legs, causes abnormal gait and stance (wide-based)
Cerebrocerebellum
Cerebrocerebellar or Lateral Cerebellar Syndrome
Coordination of skilled movements
Cognitive function, attention,
processing of language
Emotional control
Damage affects mainly arms/skilled coordinated movements (tremor) and speech
Main signs of cerebellar dysfunction
Deficits apparent only upon 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
