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Reflex movement of the head and arms in response to visual and exteroceptive stimuli


A. Vestibulospinal tract

  1. Uncrossed pathway
  2. 2 ‘types’
  3. Lateral vestibulospinal tract             
  4. Medial vestibulospinal tract

B. Lateral vestibulospinal tract

  1. Origin: Lateral vestibular nucleus (also called Deiter’s nucleus)
  2. Afferents to lateral vestibular nucleus come from
  3. Vestibular nerve – Fastigial nucleus of the cerebellum

C.  Medial vestibulospinal tract

  1. Origin: Medial vestibular nucleus
  2. Function of vestibulospinal tract

Excitatory to antigravity muscles (stimulates the extensors and inhibits the flexors) of neck and back muscles.


D. Reticulospinal tract

  1. It is a rely station for descending motor commands
  2. Origin: from reticular formation
  3. Afferents to reticular formation come from

a.  Cerebral cortex

b.  Intermediate nuclei of cerebellum

  1. 2 ‘types’

a.  Lateral reticulospinal tract            

b.  Medial reticulospinal tract


E.  Lateral reticulospinal tract

  1. Both crossed and uncrossed pathway
  2. Origin: reticular formation in medulla
  3. Function
  4. Facilitatory influence on flexors; inhibitory influence on extensors

F.  Medial reticulospinal tract:

  1. Crossed pathway
  2. Origin: from reticular formation in pons

G. Function

Inhibitory influence on flexors, facilitatory influence on extensors


H.  Basal ganglia

(There is one on each side)

It consist of:

  1. Caudate nucleus               
  2. Putamen           
  3. Globus pallidus

I.   Plus the functionally related

  1. Subthalamic nucleus (body of Luys)        
  2. Substantia nigra

The caudate nucleus and putamen is referred to as the striatum and the putamen and the globus pallidus as the lenticular nucleus.

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