Unit 5 - Cortical Control of Movement Flashcards
Overview of control of movement
What do the basal ganglia and cerebellum act as
Dimmer switches
Upper vs lower motor neurons in the control of movement
Initial idea, planning, initating & executing movement - where do they originate
How do the primary motor and pre motor cortex differ in function
Pre motor cortex - PLANNING
Primary motor cortex - INITIATING
How do the primary and premotor cortex carry out their functions (ie what tract is involved)
Each area projects directly to spinal cord via CORTICOSPINAL TRACT
and indirectly via brainstem pathways (EXTRAPYRAMIDAL TRACTS)
What is the motor cortex responsible for
Planning, shaping and initiating movements
Where is the primary motor cortex
Pre central gyrus
Brodmanns area 4
Where are pyramidal cells found
What tract do they connect to
Layer 5
Direct connections to corticospinal tract
What does stimulation of discrete motor cortical areas produce
Contralateral muscle contractions
Muscles are represented by column of neurons
Not as organised as somatosensory cortex
What does the motor cortex encode
Motor cortex encodes purposeful and precise motor movements
Control individual movements or sequences of movements that require the activity of multiple muscle groups
Encodes the force of a movement - minority of primary motor cortex neurons encode individual muscle force - a large number encodes the amount of force necessary for a particular movement
When do neurons fire when the primary motor cortex encodes a movement
5-100 msec before onset of movement
Relaying motor commands to the alpha motor neurons that eventually cause the appropriate muscles to contract
Relating to movement, what does the primary motor cortex encode
- Force
- Direction - 1 cell may fire strongly when the hand is moved to the left, and inhibited when the hand is moved to the right
- Extent - the firing of some neurons is correlated with the distance of a movement
- Speed
Function of premotor cortex
Where does it get info from
How does it influence motor activity (i.e via what connections)
Selects movements appropriate to context of action - complex task related movements
Information travels from parietal lobe, prefrontal cortex, cerebellum and basal ganglia
Influences motor activity via connections to
- Primary motor cortex
- Corticospinal - 30% of corticospinal tracts
- Corticobulbar tracts
Describe the movements the premotor cortex is involved in
When is it most active
What does damage result in
- Co-ordinated contraction of more than 1 joint
- More COMPLEX movements than primary motor cortex
- Involved in orienting the body towards a stimulus
- Most active during the early learning phases of a movement sequence, or when modifications are needed
- Difficulty developing motor strategies when damaged
When do neurons of the lateral premotor cortex fire
In anticipation of a movement
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What do the corticospinal and corticobulbar (neck down) tracts do
Initiate complex voluntary movement
LATERAL - 90%
VENTRAL - 10%
ipsilateral side
How are lower motor neurons organised within the spinal cord
Medial => axial and proximal muscles
Lateral => distal muscles
What does damage to motor cortex/upper motor neurons result in
Immediate flaccidity of muscles on contralateral side
Spinal shock - hypotonia => reduced activity at spine due to reduced input from upper motor neurons
AFTER DAYS
Loss of ability to perform fine movements
Increased muscle tone
Spinal circuits regain activity
Spasticity
Babinski sign (normal in babies)
Localising neurological injury by the patterns of facial weakness
Signs and symptoms of upper and lower motor neuron lesions
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