motor control Flashcards
Pathways that connect the brain to the spinal cord
Lateral pathways:
Under control of the cortex
-Lateral Corticospinal
-Rubrospinal
Ventromedial pathways: Under control of the brainstem -Anterior corticospinal -Vestibulospinal -Tectospinal -Pontine reticulospinal
Corticospinal pathways
- Originates in the motor cortex
- Moves to brainstem
- 90% decussate to form the lateral corticospinal tract
- 10% DO NOT- anterior corticospinal tract
Lateral pathway:
- Move down on contralateral spinal cord
- Synapse with LMN at level of spinal cord where they leave
Anterior pathway:
- Move down spinal cord on ipsilateral side
- Cross over inside the spinal cord before they synapse with the LMN at the level where they are going to leave
Rubrospinal
- Starts in red nucleus of the midbrain but receives imputes from same areas as the CST
- much smaller
- When corticospinal injured- pathways can be streghthened by the rubrospinal
Which part of the midbrain does the rubrospinal pathway start in?
The red nucleus
Vestibulospinal tract
- Originates in the vestibular nucleus-pons
- Stabilises the head and neck
Tectospinal tract
- Ensures the eyes stay open whilst the body is moving
- originates in the superior colliculus
Pontine and medullary rectospinal tract
Originates in the reticular nuclei of the brainstem
- Divided into medullary and pontine tracts
- Pontine innervates ipsilateral side
- Medullary innervates the ipsilateral side and the contralateral side
- Uses sensory innervation to maintain body position and balance REFLEXLY
- Innervates the trunk and antigravity muscles
Differences in Upper motor control generated in the cortex and the brainstem
In cortex:
- Controls fine voluntary movements
- Passes through lateral white matter
- Control LATERAL lower motor neurones
- Controls the distal limbs
In brainstem:
- Controls posture and balance
- passes through medial white matter
- control medial lower motor neurones
- controls proximal limbs
Which areas of the brain supply the motor units?
Area 4: Motor cortex
Area 6: pre-motor area
What is area 6 subdivided into? and what does each area supply
Pre-motor: supplies Proximal motor unit
Supplementary motor unit:supplies distal motor units
where is area 4 found
around the precentral gyrus
What does stimulation of one area of the cortex lead to?
Multiple movements- not just one
What controls our body awareness?
Proprioceptive, sensory somatic and visual inputs to posterior parietal lobe (area 5/7)
Where are decisions taken and elaborated
prefrontal and parietal lobe
When do the neurones in area 6 fire?
- When a decision is made
- When a decision is being planned
- When we see someone else carrying out an action -MIRROR NEURONES
Motor control is a functional hierarchy, what are its levels, their anatomical components and function?
High:
- Basal Ganglia and association neocortex
- Goal & movement strategy to achieve the goal
Middle:
- Motor Cortex & Cerebellum
- Sequence of muscle contractions to smoothly achieve the goal
Low:
- Brain stem & Spinal cord
- Activation of motor neurons and interneurons
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
