Descending Pathways

Question 1

Name the 2 types of descending pathways

Answer 1

1. Pyramidal

2. Extrapyramidal

Question 2

What 2 subcategories are there within pyramidal tracts?

Answer 2

1. Corticospinal Tracts

2. Corticobulbar Tracts

Question 3

What are the 4 subcategories within extrapyramidal tracts?

Answer 3

1. Vestibulospinal Tracts
2. Reticulospinal Tracts
3. Rubrospinal Tracts
4. Tectospinal Tracts

Question 4

Where do the the pyramidal tracts originate from?

Answer 4

Cerebral cortex

Question 5

What is the function of the pyramidal tracts?

Answer 5

Voluntary control

Question 6

Where does the corticospinal tract receive information from?

Answer 6

1. Primary motor cortex
2. Premotor cortex
3. Supplementary motor area
   (4. Somatosensory area - to regulate ascending)

Question 7

Describe the pathway of the corticospinal tract

Answer 7

• Begins in primary motor cortex
• Descends through the internal capsule
• Pass through crus cerebri of midbrain, pons, medulla
• At caudal part of medulla division occurs:
  1. Lateral corticospinal tract: decussates, terminates at ventral horn, supply muscles of body
  2. Anterior corticospinal tract: ipsilateral, decussates and terminates at ventral horn of cervical and upper thoracic levels

Question 8

Where is the most common site for haemorrhagic bleeding in the corticospinal tract?

Answer 8

Internal capsule

Question 9

Where does the corticobulbar tract originate from?

Answer 9

Lateral aspect of primary motor cortex

Question 10

Describe the pathway of the corticobulbar tract

Answer 10

• Arise from lateral aspect of primary motor cortex
• Fibres pass through internal capsule to brainstem
• Terminate at motor nuclei of cranial nerves
• Supply face

Question 11

Which 2 cranial nerves do not innervate bilaterally?

Answer 11

1. CN VII - facial

2. CN XII - hypoglossal

Question 12

Where do the extrapyramidal tracts originate from?

Answer 12

Brainstem

Question 13

What is the function of the extrapyramidal tracts?

Answer 13

Involuntary and autonomic control of CNS

muscle tone, balance, posture, locomotion

Question 14

Which of the 4 extramedullary tracts supply contralateral muscles?

Answer 14

1. Rubrospinal tract

2. Tectospinal tract

Question 15

Which of the 4 extramedullary tracts supply ipsilateral muscles?

Answer 15

1. Reticulospinal tract

2. Vestibulospinal tract

Question 16

What is the function of the vestibulospinal tract?

Answer 16

Balance and posture

Question 17

Which muscles are innervated by the vestibulospinal tract?

Answer 17

1. Flexors of the arms

2. Extensors of the legs

Question 18

Where do the 2 reticulospinal tracts originate and what is their function?

Answer 18

1. Medial: arises from pons, voluntary movement and increases muscle tone
2. Lateral: arises from medulla, inhibits voluntary movement and decreases muscle tone

Question 19

What is the function of the rubrospinal tract?

Answer 19

Fine movement of the hands

Question 20

Where does the rubrospinal tract originate from?

Answer 20

Red nucleus in midbrain

Question 21

What is the function of the tectospinal tracts?

Answer 21

Coordinate head movement with visual stimuli

Question 22

Where does the tectospinal tract originate from?

Answer 22

Superior colliculus in midbrain