Vestibulocochlear System

Question 1

Vestibulocochlear System basics

Answer 1

• Sensory for hearing and balance
• Postural control with changing body positions
• CN VIII (Vestibulocochlear N); Functionally two seperate nerves that share a sheath
  – Cochlear N: Auditory
  – Vestibular N: Balance

Question 2

Cochlear Pathway

Answer 2

• Begins in the cochlea (spiral) of the inner ear
• Primary neurons have cell bodies in the spiral ganglion
• Synapse within the cochlear nucleus at the pontomedullary junction
• Seconday neuron splits into three pathways:
  – To the ipsilateral Superior Olivary Nucleus, synapse and travel to the inferior colliculus
  – To the Contralateral Sueprior Olivary Nucleus, synapse and travel to the inferior colliculus
  – Travel directly to the ipsilateral inferior colliculus
• Inferior colliculi share commissural fibers
• Inferior colliculi send axons to bilateral medial geniculate nuclei
• Medial Geniculate Nuclei send axons on a unilateral path to the primary auditory cortex in the temporal lobe

Question 3

Some axones from the ____ go to the ____ for reflexive activation of the stapedius muscle to dampen loud sounds

Answer 3

• ipsilateral olivary nucleus
• Facial Motor Nuclei

Question 4

Why do we have a startle response from a loud noise?

Answer 4

Connections between the olivary nucleus to the reticular formation

Question 5

The primary auditory cortex =

Answer 5

notice sound

Question 6

Seconday Auditory Cortex =

Answer 6

interpret sound

Question 7

Where and what is wernicke’s area?

Answer 7

• Superior temporal gyrus of the left hemisphere (90% of the population)
• Interprets the meaning of speech

Question 8

Where and what is Broca’s Area?

Answer 8

• Specialized part of the inferior frontal gyrus and is part of the motor association area
• Creates spoken language

Question 9

How does wernickes and brocas communicate?

Answer 9

Arcuate fasiculus

Question 10

Lesions in the broca’s area will cause

Answer 10

expressive (or motor) aphasia

Question 11

Lesions in wernicke’s area causes

Answer 11

Receptive aphasia

Question 12

Recovery from broca or wernicke damage is good, why?

Answer 12

It can switch its function to the opposite side of the brain

Question 13

Semicircular canals

Answer 13

• Fluid filled at 90 degrees
• Movement of fluid gives sensation of the position of the head
• Two semicircular canals, one on each side

Question 14

Saccule

Answer 14

Hair cells that detect acceleration

Question 15

Otoconia

Answer 15

• Crystals that move on the mass like jello
• Give acceleration and deceleration information
• If they break off and get into the smicircular canals can lead to vertigo and other vestibular problems

Question 16

Vestibular Pathways basis

Answer 16

• Sensory for balance and motion (Eyes, head and neck position and postural control input)
• Primary neuron start in the semicircular canals
• Cell bodies in the vestibular ganglion
• 4 Vestibular Nuclei locate between Pons and Medulla; Assume as one

Question 17

What are the 5 Vestibular Pathways

Answer 17

• Vestibulocerebellar
• Vestibulospinal
• Vestibuloocular
• Vestibulocortical
• Accessory

Question 18

Vestibulocerebellar Pathway

Answer 18

• Feedback mechanism between cerbellum and Vestibular Nuclei
• Information concerning modifications to the motor planning for vestibular nucleus
• Vestibular to Cerebellum and back

Question 19

Vestibulospinal Pathway

Answer 19

• Direct activation of the muscles for postural control and balance
• Medial Vestibulospinal tract: bilateral innervation (Modies head position; shorter)
• Lateral vestibulospinal tract: Unilateral (moderate postural control reponses, longer)
• Begins at the vestibular Nucleus at the pontomedullary junction

Question 20

Vestibuloocular Pathway

Answer 20

• Coordinates eye and head movements, so eyes can remained fixed upon a subject even while the head moves (gaze stabilization)
• Secondary neurons from the Vestibular Nucleus ascend via Medial Longitudional Nucleus to the Paramedian Pontine Reticular Formation
• Fibers then sent out to the abducens, trochlear and oculomotor nuclei in pons and midbrain

Question 21

What happens when vestibuloocular input from the two vestibular organs is different? How do we treat it?

Answer 21

• Signal comes in and one says something different than the other (ex: crystal got in one, changes the dynamic, results in change in sensory signal. Get nystagmus and dizziness. Mismatch of one side vs the other.
• Treat: Positioning technique for crystal; vitiation exercises (do things that gradually set off the system) these symptoms suck and is hard to get compliance. Brain will start to learn what the signals mean.

Question 22

Vestibulocortical Pathway

Answer 22

• Perception of balance, movement and dizziness suggests connection between thalamus and cerebral cortex.

Question 23

Accessory Pathway

Answer 23

• Indirect control of the postural muscles via cerebellum and reticular formation
• Vestibular Nuclei go to the Cerbellum via inferior cerebellar peduncle
• Fibers exit cerebellum via inferior cerebellar peduncle and travel to the reticular formation in the brainstem
• Fibers travel both crossed and uncrossed to the LMN in the spinal cord via Reticulospinal tract

Question 24

What word describes vertigo?

Answer 24

Spinning

Often also have nystagmus

Question 25

What does nystagmus look like? How do you know what side is effected?

Answer 25

* Result is a repetitive lateral movement of the eyes toward the effected side (side with vestibular problems) and then back to center.