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Are you hearing what I am hearing...
In humans and other mammals, the auditory receptors are found in the inner ear and the whole structure for hearing consists of the outer ear, the middle ear and the inner ear.
The outer ear consists of three important components, the pinna or the ear itself, the auditory canal and the tympanum or the eardrum. Most mammals are able to move their pinna in order to pick up the source of the sound and to maximize the sound input.
The middle ear consists of mainly bones, the three important bones, the malleus, incus and the stapes.
These three bones are also known as the hammer, anvil and stirrup respectively due to their functions.
Acting together as a jointed lever, these bones transfer the vibrations of the eardrum to a thin membrane in the inner ear.
The inner ear consists of the cochlea, which is the lengthy fluid-filled tube, which is coiled like a snail shell, and the vestibular apparatus. The cochlea is U-shaped and contains sensory neurones involved in hearing. At one end of the cochlea is an oval window to which the stapes is affixed while the other end contains the round window.
Sound striking the eardrum is transferred by the bones in the middle ear unto the oval window of the cochlea, causing the fluid in the cochlea to vibrate. In the middle of the cochlea is the organ or Corti. Auditory receptors are found in this organ which converts the vibrations in the fluid of the cochlea into impulses which are then transmitted by the auditory nerve to the brain where the impulses are interpreted.
The ear also have an important function, that is to detect the direction of gravity or gravity reception. The vestibular apparatus of the inner ear detects body movements, balance and position. The vestibular apparatus comprises of semicircular canals, their ampullae, the saccule and the utricle. These structures are closely related to the sense of hearing and their specific arrangement permits them to detect changes in movement in any direction. The semicircular canals contain fluid. The movement of the fluid stimulates sensory neurones which then send impulses to the brain which would then interpret the position of the body. The saccule and utricle contain special sensory hairs which are coated with fine grains of calcium carbonate. Shifts in the position of these grains of calcium carbonate crystals results in different neural impulses produced by the sensory hairs, hence providing the brain with information about the position of the head with respect to gravity. Immediate action could then be taken to restore normal conditions.
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