Descending Extrapyramidal Motor Pathway

Question 1

What is the function of the tectospinal tract

• where does it get input from
• where does the tract start
• where does it decussate and synapse

What is the blood supply

Answer 1

Head mv in response to visual, auditory stimuli

Excitatory to optic nerve => sup colliculus

Decussate, synapse at cervical SC

SC

Question 2

What is the function of the vestibulospinal tract

• what are the 2 branches
• where do they get input from
• what do they innervate

What is the blood supply

Answer 2

Balance, posture at pontomedullary junction

Lateral (+ve, leg ext, arm flex, trunk)

• cerebellar input => inhibitory
• vestibular input => excitatory
• lateral vestibular nucleus, ipsilateral fibres onto interneurons

Medial (-ve, head and neck)

• vestibular input => inhibitory
• medial vestibular nucleus, bilateral fibres onto cervical SC neurons

AIC
Circumferential branch of Basilar

Question 3

What is the function of the rubrospinal tract

• where does the tract start
• what do they innervate

What is the blood supply

Answer 3

Fine hand mv

Red nucleus

• midbrain decussation, synapse onto interneurones
• flexor stimulatory
• extensor inhibitory

PCA

Question 4

What are the 3 functions of the reticulospinal tract

-what does each division do

Answer 4

Mediates motor function

• Medullary/lateral RST
  
  • BILATERAL => inhibit extensor spinal reflex
• Pontine/medial RST
  
  • IPSILATERAL => excites extensor spinal reflex

Mediates SNS

• VLM => IML in thoracolumbar region
  
  • innervate sympathetic preganglionic => visceral innervation

Mediates pain input

• PAG releases serotonin onto Raphe nucleus
  
  • synapses onto enkaphalinergic interneurons in DH
  • also synapses onto primary afferent pain fibre