Auditory And Vestibular Pathways Flashcards
What is the efferent system of the auditory pathway?
- From the hair cells
- Acoustic reflex
- trigeminal motor nucleus to tensor tympani
- facial motor nucleus to the stapedius
2 protects against slow loud sounds, not rapid, stiffen the ear drum
What are the stages of the auditory pathway?
-hair cells to spiral ganglion
- brainstem, the cochlear nuclei (primary terminate here)
- superior olivary complex (trapezoid body)
- inferior colliculus (can bypass the previous)
- through the brachium to the medial geniculate nucleus of the thalamus
- through the internal capsule to the primary
auditory cortex
Each one is a neuron termination all the way to the 6th order neuron
What is the system of the auditory pathway?
Bilateral
How can you have ipsilateral hearing loss?
At or before the cochlear nucleus
What are the vestibular pathways?
Many
Mainly reflex
There is an unconscious vestibular cortex
Where are the cell bodies for the hair cells of the vestibular system?
The vestibular (scarpas) ganglion
What is the first part of then vestibular pathway?
Hair cells to the vestibular ganglion
Vestibular nuclei, superior, lateral, medial, inferior
What is the first pathway of the vestibular pathway? Typical afferent for perception
- From the superior and lateral vestibular nuclei
- Medial lemniscus to the ventroposterior nucleus of the thalamus
- Vestibular cortex (somewhere)
What is the second major output of the vestibular pathway?
Reflex
1. Vestibularspinal reflexes, lateral (limb and trunck)
Medial (upper back and neck) and inferior I’m response to head movement
What is the third vestibular output?
Eye position
Vestibulo-occular reflex (VOR)
Help position the eye during movement
What is the fourth vestibular output?
Vestibular - cerebellum
Through the folliculonoduoar lobe
What travels through the internal auditory meatus?
Facial nerve
Labryinth artery
Auditory nerve
Where is the entry point of the auditory nerve?
The pons and medulla dividing point
What landmark do you look for to find the auditory nerve?
The inferior cerebellum peduncle
Where can you find the vestibulospinal tract and where does it come from and go?
Cervical spinal cord
Centrally by the fissure
The vestibular nuclei
How can you identify the mid medulla?
By the inferior olivary nucleus (not part of the pathway)
Where is the nucleus of the solitary tract?
Mid medulla
Where do the vestibular nuclei sit?
Lateral to the ventricle
Mid medulla
Inferior has speckles
Above the solitary tract and nucleus
Where is the medial longitudinal fasciculus?
Midline of the mid medulla
Where do you see the cochlear nucleus?
The rostal medulla Which you can tell by the opening of the fourth ventricle Inferior olivary nucleus Most lateral aspect of the brainstem Medial and inferior vestibular nucleus
What auditory nerve pathway do you see in the lower pons?
Superior olivary nucleus in the middle
Facial nucleus wrapping around the abducens nucleus
Superior vestibular nucleus above the facial nucleus
What do you see in the rostal pons?
MLF - medial longitudinal folliculus
Lateral lemniscus
What are the landmarks of the midbrain?
Decussation of the cerebral peduncle
What are the auditory structures of the midbrain?
Inferior colliculus
Brachium
What do you see in the rostal midbrain?
Medial (auditory) and lateral(visual) geniculate nucleus
How do you access auditory function?
Auditory brainstem response
BAER
Extremely heavily myelinated in this area
What do you see in a Auditory brainstem response?
Five peaks 10ms
- Auditory nerve
- Cochlear nucleus (trapezoid body)
- Brachium of inferior colliculus
- Cortex
- Cortex
What circuit do you think about with the weber test?
Sound localization
Left cochlear nucleus to both sides of the superior olivary nuclei
What parts of the superior olivary nucleus do you have intensity and time processing?
Lateral superior olivary nucleus - intensity
Medial superior olivary nucleus - time
