Motor 1

Question 1

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

Answer 1

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 2

How do we divide the motor tracts?

Answer 2

Into:
Ventromedial white matter tracts:
- Tectospinal
- Anterior CST
- Vestibulospinal
- Pontine & Medullary Reticulospinal Tracts

Lateral white matter tracts:

• Rubrospinal
• Lateral CST

Question 3

What tracts are contained in the ventromedial white matter and what do they control?

Answer 3

• Vestibulospinal
• Tectospinal
• Recticulospinal

They control posture and locomotion, originating in the brainstem

Question 4

What tracts are within the lateral white matter and what do they control?

Answer 4

Corticospinal & Rubrospinal

They control voluntary movements, with inputs from the cortex

Question 5

Whats the function of the vestibulospinal tract?

Answer 5

It takes signals from the vestibular system through the CrNVIII nuclei to the spinal cord to stabilize the head & neck

Question 6

Whats the function of the tectospinal tract?

Answer 6

Maintains eye stability as the body moves

Originating in the Superior Coliculus

Question 7

Whats the function/origin of the recticulospinal tracts?

Answer 7

Split into pontine & medullary origins

They handle reflexive control of posture & balance using trunk & anti-gravity limb muscles

Question 8

Whats the function of the Corticospinal (CST) tract?

Answer 8

Conscious skeletal muscle control originating in the Primary Motor Cortex

Question 9

Whats the origin of the rubrospinal tract? (RST)

Answer 9

Starts in red nucleus of the midbrain

Question 10

For comparison what tracts does pain and general sensory info travel the spine in?

Answer 10

Spinothalamic

• Ventrolateral White matter
• Carries 2nd order pain fibres from contralateral body

Dorsal Column
- Carries ipsilateral general sensory info in the dorsal white matter by the dorsal horn

Question 11

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?

Answer 11

You lose the movements as before but after a few months the RST takes over and you regain fine motor control

Question 12

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

Answer 12

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 13

What areas of the cortex are involved in motor control?

Answer 13

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 14

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

Answer 14

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 15

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

Answer 15

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

Question 16

Area 6 neurons fire roughly 1second before we make a movement, when else do they fire?

Answer 16

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