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Section II: Sensory Systems
11. Vestibular System: Pathways and Reflexes
Part 2 of 2

Lincoln Gray, Ph.D.
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Lateral and Medial Vestibulospinal Tract

Figure 11.5 shows details of the lateral vestibulospinal tract. As the name suggests, this tract arises in the lateral vestibular nucleus. The tract descends through the inferior vestibular nucleus, giving this nucleus its "salt and pepper" appearance. Below the medulla the lateral vestibulospinal tract descends in the anterior white matter down the entire length of the spinal cord. This tract modulates postural adjustments to movements. For example, the reason we stagger after spinning is due to excess activity in the lateral vestibulospinal tract.

Figure 11.5

The lateral vestibulospinal tract.

1) Pressplayto begin the pathway.
2) Then, click on each layer to see it enlarge with the path showing OR click before playing to see the layer without the path showing.
3) Roll over a layer to identify it's name.

Figure 11.6 shows details of the medial vestibulospinal tract. As its name suggests, this tract starts in the medial vestibular nucleus. It is a bilateral tract. It descends no lower than the mid-thoracic cord. It mediates head position by controlling the muscles of the neck and shoulder.

Figure 11.6

The medial vestibulospinal tract.

1) Pressplayto begin the pathway.
2) Then, click on each layer to see it enlarge with the path showing OR click before playing to see the layer without the path showing.
3) Roll over a layer to identify it's name.

 

Test Your Knowledge

  • Question 1
  • A
  • B
  • C
  • D
  • E

The vestibular ocular recflex (VOR) depends on all of the following EXCEPT:

A. trochlear nucleus

B. medial longitudinal fasciculus

C. nystagmus

D. superior vestibular nucleus

E. lateral vestibular nucleus

The vestibular ocular recflex (VOR) depends on all of the following EXCEPT:

A. trochlear nucleus This answer is INCORRECT.

CN IV controls eye movements, and is thus involved in the VOR.

B. medial longitudinal fasciculus

C. nystagmus

D. superior vestibular nucleus

E. lateral vestibular nucleus

The vestibular ocular recflex (VOR) depends on all of the following EXCEPT:

A. trochlear nucleus

B. medial longitudinal fasciculus This answer is INCORRECT.

Vestibular afferents travel to CN III, IV and VI in the MLF, and are thus involved in the VOR.

C. nystagmus

D. superior vestibular nucleus

E. lateral vestibular nucleus

The vestibular ocular recflex (VOR) depends on all of the following EXCEPT:

A. trochlear nucleus

B. medial longitudinal fasciculus

C. nystagmus This answer is INCORRECT.

Nystagmus is a form of VOR.

D. superior vestibular nucleus

E. lateral vestibular nucleus

The vestibular ocular recflex (VOR) depends on all of the following EXCEPT:

A. trochlear nucleus

B. medial longitudinal fasciculus

C. nystagmus

D. superior vestibular nucleus This answer is INCORRECT.

The superior vestibular nucleus sends afferents to the occulomotor nuclei and is thus involved in the VOR.

E. lateral vestibular nucleus

The vestibular ocular recflex (VOR) depends on all of the following EXCEPT:

A. trochlear nucleus

B. medial longitudinal fasciculus

C. nystagmus

D. superior vestibular nucleus

E. lateral vestibular nucleus This answer is CORRECT!

The lateral vestibular nucleus contributes to a descending, not ascending, pathway, and is thus NOT involved in the VOR.

 

 

 

 

 

 

 

 

  • Question 2
  • A
  • B
  • C
  • D

Which descending vestibular pathway is ipsilateral and reaches sacral levels of the spinal cord?

A. lateral vestibular pathway

B. medial vestibular pathway

C. medial longitudinal fasciculus

D. trapezoid body

Which descending vestibular pathway is ipsilateral and reaches sacral levels of the spinal cord?

A. lateral vestibular pathway This answer is CORRECT!

B. medial vestibular pathway

C. medial longitudinal fasciculus

D. trapezoid body

Which descending vestibular pathway is ipsilateral and reaches sacral levels of the spinal cord?

A. lateral vestibular pathway

B. medial vestibular pathway This answer is INCORRECT.

The medial vestibulospinal tract is bilateral, travels in the MLF and stops at the thoracic cord.

C. medial longitudinal fasciculus

D. trapezoid body

Which descending vestibular pathway is ipsilateral and reaches sacral levels of the spinal cord?

A. lateral vestibular pathway

B. medial vestibular pathway

C. medial longitudinal fasciculus This answer is INCORRECT.

The MLF is important for the ascending vestibular pathways and for the medial vestibulospinal tract, which is bilateral and short.

D. trapezoid body

Which descending vestibular pathway is ipsilateral and reaches sacral levels of the spinal cord?

A. lateral vestibular pathway

B. medial vestibular pathway

C. medial longitudinal fasciculus

D. trapezoid body This answer is INCORRECT.

The trapezoid body is a decussation of the auditory system.

 

 

 

 

 

 

 

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