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Physiology of hearing and hearing loss

Question
7 out of 39
 

All of the following are concerned with auditory pathway except: (LQ)



A Trapezoid body
B Medial geniculate body

C Genu of internal capsule
D Laterallemniscus

Ans. C Genu of internal capsule

Organ of Corti is the sense organ of hearing and is situated on the basilar membrane.

The actual sensory receptors in the organ of Corti are two specialized types of nerve cells k/a hair cells.

Inner hair cells - single layer

Outer hair cells - 3 or 4 layers

The nerve fibers stimulated by the hair cells lead to the'spiral ganglion of Corti'which lies in the modiolus (center) of the cochleA.

The spiral ganglia has bipolar cells - Its dendrites innervate the hair cells whereas the axons form the cochlear division of CN VIII and end in the dorsal and ventral cochlear nuclei located in the upper part of medullA.

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Auditory Pathway

All the fibres from the dorsal and ventral cochlear nuclei synapse (kla Trapezoid body) and the 2° order neurons pass mainly to the opposite side of the brainstem to terminate in the superior olivary nucleus

A few 2° order fibers pass to the superior olivary nucleus on the same side

From the superior olivary nucleus, the auditory pathway passes upward through the lateral lemniscus

Some of the fibers terminate in the nucleus of the lateralleminiscus but many bypass this nucleus and travel on to the 'inferior colliculus', where all or almost all fibers do synapse.

From there, the pathway passes to the medial geniculate nucleus, where all fibers synapse.

Finally the pathway proceeds by way of auditory radiation to auditory cortex, located mainly in the superior gyrus of temporal bone.

Note

In short pathway of hearing is:

Organ of Corti

Spiral ganglion

Dorsal/ventral cochlear nuclei

(Trapezoid body)

Superior olivary nucleus

Lateral lemniscus

Inferior colliculus

Medial geniculate body

Auditory cortex.

Crossing over of the fibers from both sides occurs at 3 places in the brain.

a. At the trapezoid body

b. In the commissure between the 2 nuclei of lateral lemnisci

c. In the commissure connecting the two inferior colliculi

Physiology of hearing and hearing loss Flashcard List

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