motor control

Question 1

Pathways that connect the brain to the spinal cord

Answer 1

Lateral pathways:
Under control of the cortex
-Lateral Corticospinal
-Rubrospinal

Ventromedial pathways: 
Under control of the brainstem 
-Anterior corticospinal
-Vestibulospinal
-Tectospinal
-Pontine reticulospinal

Question 2

Corticospinal pathways

Answer 2

• 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

Question 3

Rubrospinal

Answer 3

• 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

Question 4

Which part of the midbrain does the rubrospinal pathway start in?

Answer 4

The red nucleus

Question 5

Vestibulospinal tract

Answer 5

• Originates in the vestibular nucleus-pons

- Stabilises the head and neck

Question 6

Tectospinal tract

Answer 6

• Ensures the eyes stay open whilst the body is moving

- originates in the superior colliculus

Question 7

Pontine and medullary rectospinal tract

Answer 7

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

Question 8

Differences in Upper motor control generated in the cortex and the brainstem

Answer 8

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

Question 9

Which areas of the brain supply the motor units?

Answer 9

Area 4: Motor cortex

Area 6: pre-motor area

Question 10

What is area 6 subdivided into? and what does each area supply

Answer 10

Pre-motor: supplies Proximal motor unit

Supplementary motor unit:supplies distal motor units

Question 11

where is area 4 found

Answer 11

around the precentral gyrus

Question 12

What does stimulation of one area of the cortex lead to?

Answer 12

Multiple movements- not just one

Question 13

What controls our body awareness?

Answer 13

Proprioceptive, sensory somatic and visual inputs to posterior parietal lobe (area 5/7)

Question 14

Where are decisions taken and elaborated

Answer 14

prefrontal and parietal lobe

Question 15

When do the neurones in area 6 fire?

Answer 15

• When a decision is made
• When a decision is being planned
• When we see someone else carrying out an action -MIRROR NEURONES

Question 16

Motor control is a functional hierarchy, what are its levels, their anatomical components and function?

Answer 16

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

Question 17

Explain the distribution of LMN cell bodies in the spinal grey matter?

Answer 17

They show somatotopic distribution. The more medial a limb muscle (or an axial muscle) the more medial its cell body in the grey matter

Question 18

What areas of the cortex are involved in motor control?

Answer 18

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

Question 19

What would happen if you damaged Posterior Parietal Cortex (Area 5/7)?

Answer 19

Since its responsible for the sensory somatotopic image of the contralateral body you could lose perception of one side of the body (Hemispatial Neglect)

Question 20

How does the passage of motor control descisions occur in the cerebrum?

Answer 20

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