Motor Control

Question 1

What is the motor homunculus

Answer 1

Motor homunculus is a topographic representation of the body parts and its correspondence along the precentral gyrus of the frontal lobe (essentially map of the body on the motor cortex)

Question 2

What does the motor homunculus represent

Answer 2

represents the contralateral side (e.g. primary cortex in right cerebral hemisphere represents the motor activity of the left side of the body)

Question 3

What is the readiness potential (pre-motor potential)

Answer 3

measure of activity in the motor cortex and supplementary motor area of the brain leading up to voluntary muscle movement

Question 4

What 2 disorders occur due to damage of the basal ganglia

Answer 4

Parkinson’s disease
Huntingtons disease

Question 5

What is the cause of Parkinson’s disease

Answer 5

Degeneration of neurones in substantial nigra, therefore loss of their dopaminergic (excitatory) inputs to the striatum

(Dopamine normally enhances cortical inputs through the direct pathway and suppresses the inputs of the indirect pathway)

Question 6

What is the presentation of Parkinson’s (1)

Answer 6

Hypokinesia:
- Slowness, difficult to make voluntary movements, increased muscle tone (rigidity), tremors of hand and jaw

Question 7

What causes Huntingtons disease

Answer 7

Hereditary – progressive and fatal
Caused by profound loss of caudate, putamen and globes pallidus (i.e. loss of ongoing (tonic) inhibition by basal ganglia)

Question 8

What is the presentation of huntingtons disease

Answer 8

Hypokinesia with dementia and personality disorders

Question 9

What is the sensory input at the spinal cord

Answer 9

Proprioceptors, touch, pain etc.

Question 10

What is the sensory input at the brainstem

Answer 10

vestibular system informs about balance

Question 11

vestibular system informs about balance

Question 12

What is the sensory input at the cortex

Answer 12

movements in response to: visual, olfactory, auditory, emotional, intellectual cues

Question 13

What symptoms are seen in patients with cerebellar disorders

Answer 13

Lesions to cerebellum causes Ataxia = uncoordinated and inaccurate movements
(E.g. failure to touch nose with eyes closed (similar to alcohol which depresses cerebellar circuits)

Question 14

What are the future clinical implications of understanding the brain control of movement

Answer 14

Brain-machine interfaces are being developed which allow patients to voluntarily control prosthetic limbs and walk again following spinal cord injuries

(Further developed with sensory properties so patients get sensory feedback when prosthetic limb makes contact with objects or people)