Question

Draw a labelled diagram of the ear. Write a note on the mechanism of hearing.

Answer 1

The external ear receives and collects the sound waves and then directs them to the eardrum. The sound waves travel through the external auditory canal. The eardrum vibrates and these vibrations are passed to the three ear ossicles (malleus, incus and stapes) in the middle ear.

The ear ossicles increase the intensity of the sound vibrations and transmit them to the oval window. The vibrations pass through the oval window till the cochlea where they generate the waves in the lymph present in the cochlea.

Firstly the waves are generated in the perilymph present in the scala vestibuli and then in the endolymph present in the scala media. The waves in the endolymph induce a ripple in the basilar membrane. The basilar movements bend the hair cells present in the organ of Corti pressing them against the tectorial membrane. This generates the nerve impulse in the associated afferent neurons. The impulse gets transmitted to the auditory region of the brain via the auditory nerve. The impulse gets analysed and thus the sound is recognized.