Motor control is a functional hierarchy, what are its levels, their anatomical components and function?
- Basal Ganglia and association neocortex
- Goal & movement strategy to achieve the goal
- Motor Cortex & Cerebellum
- Sequence of muscle contractions to smoothly achieve the goal
- Brain stem & Spinal cord
- Activation of motor neurons and interneurons
How do we divide the motor tracts?
Into: Ventromedial white matter tracts: - Tectospinal - Anterior CST - Vestibulospinal - Pontine & Medullary Reticulospinal Tracts
Lateral white matter tracts:
- Lateral CST
What tracts are contained in the ventromedial white matter and what do they control?
They control posture and locomotion, originating in the brainstem
What tracts are within the lateral white matter and what do they control?
Corticospinal & Rubrospinal
They control voluntary movements, with inputs from the cortex
Whats the function of the vestibulospinal tract?
It takes signals from the vestibular system through the CrNVIII nuclei to the spinal cord to stabilize the head & neck
Whats the function of the tectospinal tract?
Maintains eye stability as the body moves
Originating in the Superior Coliculus
Whats the function/origin of the recticulospinal tracts?
Split into pontine & medullary origins
They handle reflexive control of posture & balance using trunk & anti-gravity limb muscles
Whats the function of the Corticospinal (CST) tract?
Conscious skeletal muscle control originating in the Primary Motor Cortex
Whats the origin of the rubrospinal tract? (RST)
Starts in red nucleus of the midbrain
For comparison what tracts does pain and general sensory info travel the spine in?
- Ventrolateral White matter
- Carries 2nd order pain fibres from contralateral body
- Carries ipsilateral general sensory info in the dorsal white matter by the dorsal horn
IF you have a lesion of the CST & RST you lose fine motor movements of the upper limbs, what happens if it only affects the cST?
You lose the movements as before but after a few months the RST takes over and you regain fine motor control
Explain the distribution of LMN cell bodies in the spinal grey matter?
They show somatotopic distribution.
The more medial a limb muscle (or an axial muscle) the more medial its cell body in the grey matter
What areas of the cortex are involved in motor control?
The primary motor cortex (Pre-central gyrus or Area 4)
Also Area 6 is rostral (anterioventral, closer to nose) to area 4 and contains:
- Premotor Area
- Supplementary Motor Area
What would happen if you damaged Posterior Parietal Cortex (Area 5/7)?
Since its responsible for the sensory somatotopic image of the contralateral body you could lose perception of one side of the body (Hemispatial Neglect)
How does the passage of motor control descisions occur in the cerebrum?
Prefrontal cortex & Posterior parietal cortex decide on the movement
-> Axons converge on area 6
Where the movement is planned by the pre-motor & supplementary motor areas
-> Then axons travel to Area 4 (Primary motor cortex) where the neurons of the CST/RST are activated
Area 6 neurons fire roughly 1second before we make a movement, when else do they fire?
When we think about a movement or watch someone else do it.
Therefore the same motor circuits as plan our movements also allow us to comprehend other peoples movements