The middle ear is an air-filled cavity that turns sound waves into vibrations and delivers them to the inner ear. The middle ear is separated from the outer ear by the eardrum , or tympanic say: tim-PAN-ik membrane, a thin piece of tissue stretched tight across the ear canal. Sounds hit the eardrum, making it move. This movement leads to vibrations of three very small bones in the middle ear known as the ossicles say: AH-sih-kuls.
The ossicles are:. To hear properly, the pressure on both sides of your eardrum must be equal. When you go up or down in elevation, the air pressure changes and you may feel a popping sensation as your ears adjust.
They adjust thanks to the narrow Eustachian say: yoo-STAY-she-en tube that connects the middle ear to the back of the nose and acts as a sort of pressure valve, so the pressure stays balanced on both sides of the eardrum. The vibrations from the middle ear change into nerve signals in the inner ear. The inner ear includes the cochlea say: KOH-klee-uh and the semicircular canals. The snail-shaped cochlea changes the vibrations from the middle ear into nerve signals. The physiology of hearing, just like its anatomy, is very complex indeed and is best understood by looking at the role played by each part of our hearing system described above.
Sound waves, which are really vibrations in the air around us, are collected by the pinna on each side of our head and are funnelled into the ear canals. These sound waves make the eardrum vibrate. The eardrum is so sensitive to sound vibrations in the ear canal that it can detect even the faintest sound as well as replicating even the most complex of sound vibration patterns.
The eardrum vibrations caused by sound waves move the chain of tiny bones the ossicles — malleus, incus and stapes in the middle ear transferring the sound vibrations into the cochlea of the inner ear. This happens because the last of the three bones in this chain, the stapes, sits in a membrane-covered window in the bony wall which separates the middle ear from the cochlea of the inner ear. These nerve impulses follow a complicated pathway in the brainstem before arriving at the hearing centres of the brain, the auditory cortex.
This is where the streams of nerve impulses are converted into meaningful sound. All of this happens within a tiny fraction of a second…. It is very true to say that, ultimately, we hear with our brain. Hearing well depends on all parts of our auditory system working normally so that sound can pass through the different parts of the ear to the brain to be processed without any distortion.
The type of hearing problem you have depends on which part of your auditory system is not responding well. If you have a problem in the outer or middle ear, it means that there is inefficient transfer of sound to the cochlea in the inner ear. These nerve endings transform the vibrations into electrical impulses that then travel along the eighth cranial nerve auditory nerve to the brain.
In green are four rows of hair cells that respond to sound vibrations, and in red are auditory nerve fibers that convey sound information from the hair cells to the brain. Researchers at Johns Hopkins are studying the molecular mechanisms that guide the formation of hair cells. Studies such as these might be a step towards less invasive treatments for deafness in which molecular cues can be used to biologically regenerate hair cells in the cochlea.
Health Home Conditions and Diseases. The Outer Ear The auricle pinna is the visible portion of the outer ear. The ossicles amplify the sound. They send the sound waves to the inner ear and into the fluid-filled hearing organ cochlea.
Once the sound waves reach the inner ear, they are converted into electrical impulses. The auditory nerve sends these impulses to the brain. The brain then translates these electrical impulses as sound.
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