auditory and vestibular systems key points relations of external, middle and inner ear understanding...
TRANSCRIPT
AUDITORY AND VESTIBULAR SYSTEMS
Key points•Relations of external, middle and inner ear•Understanding the relationship between the cochlear and vestibular apparatus in the bony labyrinth•Structure of cochlear duct and organ of Corti•Receptor deformation and transduction•Central auditory pathways•Tonopicity – from basilar membrane to cortex•Basic knowledge of efferent pathways, auditory reflexes
•Structure of vestibular apparatus - utricle and saccule (static), semicircular canals (kinetic)•Knowledge of major central vestibular pathways•Lesions and disturbances of the auditory and vestibular systems
ReadingNolte (4th Ed), pgs 325-357Fitzgerald, pgs 130-140Kiernan (7th Ed), pgs 382-405
External, middle and inner ear – the bony labyrinth
Cochlear duct and the organ of Cortiscala vestibuli, cochlear duct, scala tympani, Reissner’s
membrane, basilar membrane, organ of Corti
Note changes in width of basilar membrane
The organ of Corti
Cochlear duct contains endolymph:
high K+, low Na+
Relations between the middle and inner earChanges in the width of the basilar membrane – vibration and frequency response
Shearing forces in the organ of Corti – mechanical deformation and signal transduction
Ascending (central) auditory pathways
Tonotopicity, lesions, feedback at just about all levels including efferent projections back to the peripheral receptors in the cochlear, reflexes
Vestibular systemBalance, equilibrium, head movements
Utricle and saccule ‘STATIC LABYRINTH’
Semicircular canal (inner ear) ‘KINETIC LABYRINTH’
Receptors and associated specializations
Cilia and kinocilium – embedded in inertial mass
Excitation when deformation towards kinocilium
Inhibition when deformation away from kinocilium
View of the horizontal ducts from above, showing how paired semicircular canals work together to provide a bilateral indication of head movement
Central pathways – vestibular nerve and nuclei, medial longitudinal fasciculus, cerebellum, vestibulospinal pathways, reticular formation, cortex
Disturbances of vestibular system – motion sickness, vertigo, Meniere’s disease
Last Slide