Mechanism of hearing
Posted Date: 30-Mar-2012
Hearing is made possible by the organs ears. They are the basic organs of hearing and balancing. The mechanism of hearing in human body is discussed in this article. This article would be helpful for the students of higher secondary classes.
Hearing ability is gift for human life and as we all know the organs which help in the same is ears. Ears also have the function of maintaining the balance of human body. Still let us analyze the mechanism of hearing here. The ability to hear is made possible by the Cochlea region of ear that is situated in the inner ear. So first of all we will have to understand the structure of Cochlea in detail to understand the mechanism of hearing.
Structure of Cochlea
As discussed earlier the ear can be subdivided into many parts. The innermost part is called inner ear. Inner ear has mainly two parts called bony and membranous labyrinth. Cochlea belongs to the membranous labyrinth part and is filled with endolymph. Cochlea is coiled shape structure and the part is made of some membranes. These membranes include Reissner's membrane, basilar membrane and tectorial membrane. The first two membranes divide the bony labyrinth containing perilymph into two parts named upper scal vestibui and lower scala tymphani. The space within cochlea is called scala media and it is situated in between the above divisions. The space within Cochlea called scala media is filled with the fluid endolymph. At the base of cochlea, the scala vestibule division enters into an opening called oval window. The vibrations pass from the middle ear to the inner ear to the inner ear part Cochlea through this opening. In the same manner at the end of scala tymphani another opening called round window has been found. This opening also opens into the middle ear. The vibrations which pass into the inner ear are mainly vibrated in the fluid which leads to the hearing purpose. On the second membrane – the basilar membrane – an organ of special function called organ of corti is found. This structure contains hair cells which act as impulse receivers. They are also called auditory receptors. The hair cells are seen in rows at the inner part of organ of corti. The basal part of these hair cells is in close contact with the auditory nerves or afferent nerve fibers and these auditory nerves are responsible for carrying auditory impulse into the brain region. A large number of processes named stereo cilia are projected from the apical end of each hair cell. Above these rows of hair cells we can see the tectorial membrane. This membrane is thin and elastic in nature. Now let us think about the mechanism of hearing using his structure.
How do we hear?
To hear the sound, the sound waves should get converted into the neural impulses and the brain region analyzes this impulses resulting in the identification of sound. This process is the base of mechanism f hearing but the same occurs in several steps. First the sound waves are caught by the external ear, Pinna. This sound wave passes through the canal and reaches the eardrum. Vibrations are produced by sound waves hit on tympanum. These vibrations are carried into the middle ear. It passes through the ear ossicles which are connected to each other. Thus the efficiency of transmission is increased by the ear ossicles. Finally it passes into the Cochlea through the oval window. The sound waves generate a impulse in the fluid lymph present within. These vibrations cause a disturbance to the basilar membrane. Thus the hair cells at the organ of corti get bent. These bent hair cells scratch on the tectorial membrane. Thus an impulse is generated. This neural signal is passed through the afferent fibers into the auditory canal. Neural signal reaches the auditory cortex region of brain via auditory nerve. The nerve impulse is further analyzed and thus sound is recognized. The process takes place very fast and we can't draw clear cut divisions between each step. Further idea about the hearing mechanism at brain is more complicated and it can be studied in higher degree classes. Now the details given are the basics of hearing mechanism and they are helpful in providing a mere view about hearing.
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