1. 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
Reading
Nolte (4th Ed), pgs
Fitzgerald, pgs
Kiernan (7th Ed), pgs

2. External, middle and inner ear – the bony labyrinth

3. Cochlear duct and the organ of Corti
scala vestibuli, cochlear duct, scala tympani, Reissner’s membrane, basilar membrane, organ of Corti
Note changes in width of basilar membrane

4. Cochlear duct contains endolymph:
high K+, low Na+
The organ of Corti

5. Relations between the middle and inner ear
Changes in the width of the basilar membrane – vibration and frequency response

6. Shearing forces in the organ of Corti – mechanical deformation and signal transduction

7. Ascending (central) auditory pathways
Tonotopicity, lesions, feedback at just about all levels including efferent projections back to the peripheral receptors in the cochlear, reflexes

9. Balance, equilibrium, head movements
Vestibular system
Balance, equilibrium, head movements

10. Utricle and saccule ‘STATIC LABYRINTH’
Semicircular canal (inner ear) ‘KINETIC LABYRINTH’
Receptors and associated specializations

11. Cilia and kinocilium – embedded in inertial mass
Excitation when deformation towards kinocilium
Inhibition when deformation away from kinocilium

12. View of the horizontal ducts from above, showing how paired semicircular canals work together to provide a bilateral indication of head movement

13. 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

14. Last Slide