Motor Control I,II and III Flashcards
What are the 3 levels of motor control?
High
Middle
Low
What is the function of high motor control?
Strategy
The goal and the movement strategy
to best achieve this goal
Wanting to do something
What is the function of middle motor control?
Tactics
The sequence of spatiotemporal muscle contractions to achieve a goal smoothly and accurately
What is the function of low motor control?
Execution Activation of motor neuron and interneuron pools to generate goal-directed movement
Actually doing it
What structures are involved in high centre motor control?
Neocortex
Basal ganglion
What structures are involved in middle centre motor control?
Motor cortex
Cerebellum
What functions are involved in low centre motor control?
Brainstem
Spinal cord
What do lateral pathways control?
Voluntary movements of distal muscles
What do ventromedial pathways control?
Posture and locomotion
What are the ventromedial pathways?
- Tectospinal tract
- Vestibulospinal
- Reticulospinal
What are the lateral pathways?
Lateral and anterior Corticospinal tract
Rubrospinal tract
Which is the largest descending pathway?
Lateral corticospinal
Where does 2/3 of the CST originate?
Area 4 and 6
What does the CST control?
VOLUNTARY motor control
Where does the CST decussate?
Medulla
Which side of the body does the right motor cortex control?
Left side of the body
Where do upper CST axons synapse with LMN?
Ventral horn
Where does the RBS originate?
Magnocellular red nucleus of midbrain
Where does RBS recieve its inputs from?
Same cortical areas as CST
Areas 4 and 6
If you lesion the CST what can happen?
The RBS can in time take over function
If you lesion both the CST and RBS what happens?
Lose restored functions
Can the RST assume almost all the duties of the CST when the CST is lesioned?
Yes
What is the function of the vestibulospinal tract?
Maintains posture by detecting movement of the head
What is the function of the tectospinal tract?
Give reflex movement based on visual stimuli
Does the TST decussate?
Yes
What does the TST co-ordinate?
Eye movements and reflexes
Do VST decussate?
No
Which ventromedial pathways control muscle tones and reflexes?
Pontine reticulospinal tract
Where do pontine and medullary reticulospinal tracts originate?
Reticular formation of pons and medulla
Which ares of the brain control precise voluntary movement?
Primary motor cortex
And pre-motor areas
How do UMN from cerebral cortex control LMN?
Cross over to control the LMN in lateral and medial ventral horns
What is the precentral gyrus?
Primary motor cortex
Where do a mosaic of premotor areas lie?
Rostrally to the primary motor cortex
What is area 4?
Primary motor area
What is area 6?
Pre-motor area
What does the central sulcus separate?
Primary motor area
From primary sensory area
What is meant by the somatotopic maps in humans?
Specific areas in the brain control very specific parts of the body
E.g a specific area on the pre-central gyrus in the brain will control all movements of the hands
Does the body map into the brain in a proportionate way?
No
Completely disproportionate
Why is the somatotopic map disproportionate?
Because some parts of the body although small can be highly sensitive and require very fine tuning
What are the 2 somatotopic maps in area 6?
Premotor area
Supplementary motor area
Is the somatotopic motor map precise?
No
Does one cell in the motor cortex stimulate one certain muscle?
No
What generates mental image of body in pace?
Somatosensory, proprioceptive and visual inputs from posterior parietal cortex
Where are decisions made about what actions/movements to take and their likely outcome?
Motor areas
And their association areas
If you only think about doing a movement but do not carry the movement out which part of the brain is active?
Area 6
What are the 2 reticulospinal tracts?
Pontine
Medullar reticulopsinal tract
Where does the RST decussate?
As the fibres emerge from the red nucleus
What does the anterior CST control?
Voluntary movement ofp proximal muscles
Does one cell in the motor cortex stimulate one certain muscle?
No
Stimulating a certain area will lead to an overall behavious
When do neurons in the premotor area begin firing AP?
One second before a movement occurs
What does babinski’s signs indicate?
UMN lesion
Where does major subcortical input to area 6 come from?
Ventral lateral nucleus in dorsal thalamus
Function of basal ganglia
Modulating, refining and terminating movements and decisions made by the cortex
What composes the corpus striatum?
Caudate nucleus and putamen
What are the input zones of the basal ganglia?
Caudate nucleus
Putamen
What makes up the lentiform nucleus?
Putamen and globus pallidus
Where does the corpus striatum receive input from?
All over the cortex
What do neurons in the putamen and caudate nucleus receive from the motor cortex? direct pathway
Excitatory (glutamergic) cortical inputs on dendrites
Where does major subcortical input to area 6 come from?
VLo from thalamus
What are the components of the basal ganglia?
Caudate nucleus
Putamen
Globus pallidus
Substantia nigra
Where is the substantia nigra located?
Midbrain
Describe the cortex -> basal ganglia -> thalamus -> SMA pathway? Direct pathway
- Motor cortex sends an excitatory message to the striatum (putamen and caudate nucleus)
- Excitatory neuron synapses with an inhibitory neuron in the striatum
- This inhibitory neuron then heads for the globus pallidus
- Inhibitory neuron in the striatum is more excited than normal due to the excitation message from the cortex
- When the globus pallidus is inhibited its activity it turned down
- Meaning it can no longer inhibit the thalamus
- Thalamus is more active (VLo)
- Sends more excitatory messages to the SMA (supplementary motor area)
- So functional consequence of cortical activation of putamen is excitation
Where does the motor cortex send excitatory signals to? direct pathway
Striatum
What is the effect of excitatory signals to the striatum? direct pathway
Excitation of an inhibition pathway to the globus pallidus
Where does the enhanced inhibitory pathway from the striatum go to? direct pathway
Globus pallidus
What is the effect of the inhibitory signals to the globus pallidus? direct pathway
Inhibits it further
At rest what does the globus pallidus do to the thalamus?
Inhibits it
What does area 6 require for decision making?
Signals from the thalamus
When the globus pallidus is inhibited what can now proceed? Direct pathway
The thalamus is uninhibited and can send VLo signals to area 6
What is the functional consequence of cortical activation of putamen? direct pathway
Excitation
When there is a lot of cortical input to the basal ganglia what happens?
The globus pallidus is inhibited and therefore the thalamus is disinhibited and so can excited neurones in SMA
What is Parkinson’s disease caused by?
Degeneration of neurons in the substantia nigra and their domaninergic input to the stiratum
Which neurotransmitter is affected in Parkinson’s disease?
Dopamine
How does dopamine affect pathways?
can enhance cortical inputs through the “direct” pathway and suppress inputs through “indirect” pathway
What happens in the depletion of dopamine?
Closes down the activation of the focussed motor activities that funnel through the thalamus to SMA
What causes huntington’s disease?
caused by profound loss of caudate, putamen and globus pallidus
What is there a loss of in Hungtington’s disease?
Inhibitory effects of the basal ganglia
What % of neurons of the brain are located in the cerebellum?
50%
What does the cerebellum introduce to the cortex?
Further refinement
What do lesions to the cerebellum produce?
uncoordinated inaccurate movements : ataxia : fail to touch nose with eyes shut
What does the cerebellum instruct?
Direction, timing and force
What does VLo mean?
Ventrolateral thalamus
