Physiology of Ear and Hearing

Sense organs that is eye, ear, nose, tongue and skin provide a true sense to communicate with the outer world. Ear is the organ of hearing and balance. Ear is a complex organ consisting of three divisons, the outer, middle, and inner ear. The structures of the external ear are auricle, external auditory meatus and outer layers of the tympanic membrane. The middle ear is an air filled cavity (tympanum) consists of ear ossicles, auditory tube (Eustachian tube), middle ear muscles, inner layer of the tympanic membrane. The internal ear consists of the osseous labyrinth consisting of cochlea, vestibule and semicircular canals and membranous labyrinths and the vestibular and acoustic (spiral) ganglia associated with the eighth cranial nerve (vestibulocochlear nerve). The auditory system of ear convert sound waves into neural signals. The auricle acts as a condiut to collect the sound waves. The middle ear acts as a precochlear amplifier and impedance matching device. Transduction of sound occurs in the cochlea by spiral organs (formerly known as organs of Corti) resulting in an action potential that transmits along the auditory nerve to cochlear nucleus in the brainstem for hearing. The vestibular system plays an important role in maintaining the equilibrium and balance of the animal. It is a primary sensory organ consisting of vestibule and semicircular canals which orients with respect to the gravitational field of the earth and co-ordinates the movement of various sensory organs and thus the linear, rotatory, acceleration and deacceleration movements of the animal. 

Keywords: Auricle, Balance, Basilar membrane, Cochlear duct, Crista ampullaris, Ear, Ear ossicles, External auditory meatus, Hair cells, Hearing, Impedance, Macula, Membranous sacculus, Membranous utriculus, Organ of Corti, Semicircular duct, Stereocilia, Tectorial membrane, Tympanic attenuation reflex, Tympanum.