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Flashcards in Auditory System Deck (20):

Lecture 1

Cochlea and the Organ of Corti


What are decibels?

Units of sound pressure/loudness.


What are the components of the outer ear?

External auditory canal. Eardrum.


What are the components of the middle ear?

Malleus. Incus. Stapes. Eustachian tubule.


What are the components of the inner ear?

Semi-circular canal. Auditory canal. Cochlea. Vestibular nerve. Endolymphatic sac.


What are the 3 chambers of the cochlea?

Scala Vestibuli. Scala Media. Scala Tympani.


How is the scala media different to the other two chambers?

High concentration of potassium ions.


What are the components of the Organ of Corti?

Outer hair cells. Inner hair cells. Tunnel of Corti. Spiral limbus. Inner spiral sulcus. Outer spinal sulcus. Tectorial membrane. Hensen's cells. Claudius' cells. Deiter's cells. Reticular lamina.


What are the main functional components of the Organ of Corti?

Hair cells.


Describe the signal transmission in the Organ of Corti.

If hair cells bend towards Kinocillium they depolarise. If hair cells bend away from Kinocillium they hyperpolarise the cell. The signal is then sent to the spiral ganglion in the mediolus.


Describe the organisation of hair cells in the Organ of Corti.

3 rows of outer and 1 row of inner hair cells. All oriented in the same direction. Joined by tiplinks for unidirectional movement.


Lecture 2

Hair cells


Describe the innervation pattern of hair cells.

3000 hair cells in cochlea. 33,000 cells in spiral ganglion. 90% of afferent ganglion fibres innervate the inner hair cell row.


Why are hair cells innervated with efferent fibres?



What is the structure of the basilar membrane?

Made up of collagen fibrils. Connected to cochlea via rounf window. High freq. at the beginning; low at the end. Terminates at its helicotrema.


What is a resonant frequency?

Frequency at which an object vibrates. Different in different regions of cochlea.


What is the role of the tectoral membrane?

Pushes on hair cells upon deflection of the basilar membrane.


What is the resting potential of hair cells?

minus 52mV


How are hair cells tuned?

Mechanically via length of hair bundle. Electrically via sinusoidal potential response.


Describe the steps of sinusoidal membrane potential changes in hair cells.

Potassium influx caused by bending of hair towards Kinocillium. Calcium influx causes rise in intracellular Ca2+ and mitochondrial uptake of Ca2+. Activation of calcium sensitive potassium channels causes potassium efflux. Further efflux by potassium VGCs. Efflux of calcium via the calcium pump.