Lecture 35 - Vestibular system Flashcards
What is the task of the auditory system?
Transduce vibration into electrical activity
What are the tasks of the vestibular system?
Senses head movements
Maintain visual axes when head is moving
Send motor commands to trunk and limb muscles to maintain balance
What are three sections of the membranous labyrinth?
Utricle - Saccule - Semicircular ducts
What is the function of the utricles?
Monitor and activate response to linear acceleration of horizontal movements
What is the function of the saccule?
Monitor and activate response to linear acceleration of vertical movements
What is the function of the Semicircular ducts?
Monitor and respond to angular acceleration of head in all planes
What is the orientation of the semicircular ducts?
Anterior - Lateral - Posterior
What neural structure is associated with the vestibular system?
Scarpa’s ganglion - vestibular ganglion
What is the electrolyte composition of the perilymph?
Increased Na concentration
What is the electrolyte composition of the endolymph?
Increased potassium concentration
What are three main structures in an ampulla?
Crista - Cupula - Hair cells
What are the three main structures of the hair cells?
Stereocilia - Kinocilium - Afferent/Efferent fibers
What fluid are the hair cells sitting in?
Endolymph
What happens within the ampulla when the endolymph is moving?
Bends cupula, which in turns tilt the stereocilia and kinocilium
What structure contains the ampullas?
Semicircular ducts
What structure are the hair cells embedded into?
Crista
What are the structures in the otolithic organs?
Otolithic membrane, Otoconia, Macula, Striola
What are the two otolithic organs?
Utricle and saccule
What is moved with the head is moved within the otolith organs?
Cap of statoconia movies, causing bending of the hair cells
What happens in the otolith organs when the sterocilia bend toward the kinocilium?
Hair cells depolarize
What molecular structure is linked to the depolarization of the hair cells?
Tip link
What does the tip link do?
Opens mechanically gated K+ channels
More voltage gated calcium channels open
Increase glutamate release
What happens in the semicircular ducts when the stereocilia are deflected towards kinocilium?
Apical K+ channels open
Depolarization of the cell membrane
Calcium channels open
Synaptic vesicles to open
What nerve is affected when the hair cells are depolarized?
Afferent nerve firing is increased
What happens when the stereocilia deflected away from kinocilium?
Decreased firing rate
What are the four vestibular nuclei?
Superior - Inferior - Medial - Lateral
What is VOR?
Vestibular reflex with the function of keeping the eyes on an object when the head is in motion relative to that object
How is the VOR carried out?
Contraction of the extra-ocular eye muscles required to keep that image of that object focused on the fovea
What happens when there is a lesion on the vestibular portion of the CN VIII, vestibular apparatus, or nuclei?
Perception of moving when not
What are the components of the spiral organ?
Outer hair cells
Inner hairs
Inner hair cell
Where is low frequency sound processed?
Towards the helicotrema
Where is high frequency sound processed?
Toward the oval window
What scala interacts with the oval window?
Vestibuli
What scala interacts with the round window?
Tympani
What is a sound wave?
Pressure displaces scala vestibuli which displaces cochlear duct and spiral organ
What projects into the tectorial membrane?
Stereocilia
What nerve goes into the scala tympani?
Cochlear nerve through the spiral ganglion
How does a hair cell depolarize?
Hair cells bend towards the kinocilia
Opens the mechanically gated potassium channels
More Ca2+ voltage gated open
Glutamate released
What is auditory information delivered to and processed in?
Auditory cortex
