Motor Control

Question 1

What neurotransmitter does the Substantia Nigra secrete and what affect does this have on the basal ganglia (in initiation of muscle movement)?

Answer 1

SN releases Dopamine

Dopamine enhances cortical inputs through the direct pathway; and suppressed inputs through the indirect pathway.

Explanation:
Dopamine excites the INHIBITORY signal from the Striatum (Caudate and Putamen) on it’s way to the Globus Pallidus - this increases the inhibition of the thalamus, thus releasing the Motor Cortex from inhibition and increases excitatory signals to the muscles

Question 2

Where does the Corticospinal Tract originate, where does it decussate and what does it control?

Answer 2

Motor Cortex

Decussate near level of termination

Voluntary, fine skilled movements of distal limbs

Question 3

The tectospinal and the vestibulospinal tract are both under brainstem control - how do they differ?

Answer 3

Tecto - fixes eyes when everything else is moving, originate in the superior colliculi (in midbrain)

Vestibulo - stabilises head and neck, originates in the Vestibular Foramen of the Pons (or Medulla)

Question 4

What do Brodmann Areas 4 and 6 correspond to?

Answer 4

The Motor Cortex (4) and Pre-motor cortex (6)