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Although Sensorineural hearing loss is only one of the three main causes of hearing impairments, close to 90 percent of all hearing loss cases are caused by it. Sensorineural hearing loss refers to cases in which the auditory nerve or the cochlea, located in the inner ear, are damaged. The two sensorineural hearing impairment types are congenital hearing loss and acquired hearing loss.
When the sensorineural damage happens because of the natural aging process it is called presbycusis. Another common reason for sensorineural hearing loss is exposure to high decibel noises over a period of time. It is well known that exposure to noise levels that exceed eighty five decibels may damage the inner ear air cells and even the auditory nerve itself. Other possible causes include various infections and diseases that can damage the inner ear, physical trauma and tumors.
Like with all other types of hearing loss, awareness and early detection can help in avoiding further deterioration or experiencing unwanted side effects such as social isolation and depression. Tom Regev is a professional writer representing the Hearing Aids Edison NJ audiology center.
Medical Disclaimer Statements on Get Holistic Health about health issues aren't meant to identify, treat, cure, or protect against illness. The pinna is a prominent skin-covered flap located on the side of the head, and is the visible part of the ear externally.
The tympanic membrane is commonly known as the eardrum, and separates the ear canal from the middle ear.
The tympanic cavity contains the body’s three smallest bones and two smallest muscles. IncusThe incus is connected to the malleus on the side closer to the eardrum, and to the stapes on the side closer to the inner ear.
Stapedius and Tensor tympaniThe stapedius is the muscle of the inner ear that inserts on the stapes. As the eardrum vibrates in response to air waves, the chain of inner ear bones are set into motion at the same frequency. The inner ear is the deepest part of the whole ear, and is located in a place known as the bony labyrinth, which is a maze of bone passageways lined by a network of fleshy tubes known as the membranous labyrinth. Arising from the vestibule is the cochlea, which is sometimes referred to as the organ of hearing, as it is the part of the whole ear that actually converts sound vibrations to the perception of hearing.
The function of the auditory ossicles in the middle ear is to concentrate the energy of the vibrating eardrum so as to create a greater force per unit area at the oval window, as previously described. In addition to this, the ossicles and their adjacent muscles also serve a protective function.
The muscles of the middle ear also assist in coordinating speech with hearing, so that the sound of our own speech is not so loud as to damage our inner ear and drown out soft or high-pitched sounds from other sources. The inner hair cells transform the mechanical force of sound (cochlea fluid vibration) into the electrical impulses of hearing (action potentials sending auditory messages to the brain). Unlike the inner hair cells, the outer hair cells do not signal the brain about incoming sounds. The activity of the inner and outer hair cells is possible through various other components within the cochlear.
The vibration of the auditory ossicles, as previously described, eventually leads to the vibration of the basilar membrane on which the hair cells rest through sequence of chain reactions.
In order for inner hair cells to function properly, the tips of their stereocilia must be bathed in endolymph, which has an exceptionally high potassium ion (K+) concentration, creating a strong electrochemical gradient (large difference in voltage) from the tip to base of a hair cell. The stereocilia of the outer hair cells have their tips embedded in the tectorial membrane, while the stereocilia of the inner hair cells come very close to the membrane. A protein functions as a mechanically gated ion channel on the top of each stereocilia of the inner hair cells. The conversion of sound energy into a neural signal that is interpreted by the brain as sound perception, as described above, is known as sound transduction. Although we think of the ear as the sense organ for hearing, it did not evolve originally for this purpose. Both the saccule and the utricle contain a small patch of hair cells and their supporting cells, which collectively are known as a macula. Horizontal tilt of the head is detected by the macula utriculi, while vertical tilt of the head is detected by the macula sacculi.
When we begin to move forward after being stationary, the heavy otolithic membrane of the macula utriculi briefly lags behind the rest of the tissues. Deafness refers to a loss of hearing, which may be temporary or permanent, partial or complete.
Conductive deafness occurs when sound waves are not properly conducted through the external and middle portions of the ear to set the fluid in the inner ear in motion. In sensorineural deafness, the sound waves are transmitted to the inner ear, but they are not converted into nerve signals that are interpreted by the brain as sounds.
Vertigo refers to the sensation of rotation in the absence of equilibrium – in other words, dizziness.
Meniere’s Syndrome is a disease of the internal ear affecting both hearing and equilibrium. Hearing aids can be useful in treating conductive deafness but are less beneficial for sensorineural deafness. Obviously, old age is the main cause for sensorineural hearing loss, but there are also other elements that may influence it. The cochlea, which contains three chambers that are filled with fluids, is responsible for translating and transmitting sounds to the auditory nerve. A healthy auditory nerve is composed of nerves that transfer electric information to the brain. Annual checkups at an audiology center, especially for those over the age of fifty five, are recommended to ensure proper treatment is applied as soon as the first signs of hearing loss appear. There are two types: auditory and vestibular, responsible for hearing and balance respectively.
Hearing can be defined as the perception of sound energy via the brain and central nervous system.
It is separated from the ear canal of the outer ear by the tympanic membrane (the eardrum).
The bones are also referred to as auditory ossicles, and connect the eardrum to the inner ear.
It has a handle that attaches to the inner surface of the eardrum, and a head that is suspended from the wall of the tympanic cavity. This footplate is held by a ringlike piece of tissue in an opening called the oval window, which is the entrance into the inner ear.
The frequency of movement is transmitted across from the eardrum to the oval window (another structure in the ear), resulting in a pressure being exerted on the oval window with each vibration.
A cushion of fluid, called perilymph, lies between the bony and membranous labyrinth, while a fluid called endolymph is found within the membranous labyrinth itself. The cochlea is in the form of a snail-like spiral, so that a longer cochlea is able to fit inside an enclosed space. The upper chamber, scala vestibule, and the bottom chamber, scala tympani, are filled with perilymph.
It about the size of a pea, and acts as a transducer, converting vibration into nerve impulses.
Just as we are about to speak, the brain signals the middle ear muscles to contract, dampening the sense of hearing in coordination with the sound of our own voice. The physiology of the cochlea revolves around the functioning of the inner and outer cochlea hair cells.
They instead actively and rapidly elongate in response to changes in the voltages of the cell membrane.

During the vibration of the auditory ossicles, the stapes vibrates rapidly in and out, leading to the basilar membrane vibrating down and up, and the secondary tympanic membrane vibrating out and in. The tectorial membrane is anchored to a structure called the modiolus, which holds it relatively still as the basilar membrane and hair cells vibrate. In addition, there is a fine stretchy protein filament known as a tip link that extends like a spring from the ion channel of one stereocilium to the side of the streocilium next to it. Loud sounds produce more vigorous vibrations of the organ of Corti, thereby exciting a greater number of hair cells over a greater area of basilar membrane. It was instead originally an adaptation for coordination and balance, collectively known as the sense of equilibrium.
The macula lying vertically on the wall of the saccule is called the macula sacculi, while the macula lying horizontally on the floor of the utricle is called the macula utriculi. When the head is upright, the otolithic membrane weighs down directly on the hair cells, keeping stimulation to a minimum. When we stops moving, the macula stops as well, but the otolithic membrane keeps moving for a moment, bending the stereocilia forward.
The defect can lie in the organ of Corti or the auditory nerves, or rarely, in some pathways and parts of the brain. Vertigo can be caused by viral infections, certain drugs, and tumours such as acoustic neuroma. Patients initially experience episodes of dizziness and tinnitus (ringing noise in the ears), and later develop a low-frequency hearing loss. They increase the intensity of airborne sounds and may modify the sound spectrum to suit the patient’s particular pattern of hearing loss at higher or lower frequencies. In severe cases sensorineural damage can even lead to deafness while moderate and mild conditions can be solved with the use of proper hearing aids or cochlear implants. Material shown by Get Holistic Health is for educational purposes only and isn't meant to substitute for the recommendation of a doctor and other medical professional. Auditory hair cells function by bending in response to sound, and their movements are transmitted as electrical signals to the brain, which interprets them as sound. Hearing consists of two components: identification of sounds (what the sound is) and localisation of those sounds (where the sounds are coming from). Sound localisation for sounds approaching from the left or the right is determined in two ways. It collects sound waves and channels them down the external ear canal through patterns formed on the pinna known as whorls and recesses. Skin lines the canal, and contains glands that produce secretions that mix with dead skin cells to produce cerumen (earwax).
This produces wavelike movements of the inner ear fluid at the same frequency as the original sound wave. Within the inner ear is a chamber called the vestibule, which plays a major role in the sense of balance. It is about 9mm wide at the base and 5mm high, and winds around a section of spongy bone called the modiolus. In addition to the cells themselves, there are several other components of the cochlea that contribute to the ability to hear.
When the rate of neurotransmitter (chemicals released by cells in response to stimuli) release from these hair cells is increased, the rate of firing in the nerve fibres is also increased.
Vibration of the basilar membrane therefore causes shearing of the hair cells against the tectorial membrane, bending the hair cell stereocilia back and forth. On each inner hair cell, the stereocilia progressively increase in height, so that all but the tallest ones have tip links leading to taller stereocilia beside them. Vertebrates only evolved the cochlea, middle ear structures and consequent auditory function of the ear later on.
Each hair cell of a macula has about 40-70 stereocilia (structures on the hair cells that sense mechanical stimuli), as well as one true cilium (a tail-like cell projection) called a kinocilium. However, when the head is tilted, the weight of the membrane bends the stereocilia, stimulating the hair cells. The hair cells covert this pattern of stimulation into nerve signals which are relayed to the brain to be interpreted. Even exposure to ordinary modern-day sounds can eventually damage hair cells over long periods of time.
Vertigo can also produced normally in individuals through excessive stimulation of the semicircular ducts. The causes relate to the blockage of a duct in the cochlea which drains excess endolymph away. However, the receptor cell-neural pathway system must still be intact and functioning for the sound to be perceived, so hearing aids are useless in sensorineural deafness. They convert sound signals into electrical signals that can directly stimulate the auditory nerve, so as to bypass a defective cochlea system. The ear is divided into three main parts – the outer ear, the middle ear, and the inner ear. Firstly, the sound wave reaches the ear closer to the sound slightly earlier than it reaches the other ear. Its shape also partially shields sound waves that approach the ear from the rear, therefore enabling a person to tell whether a sound is coming directly from the front or the back. Cerumen, along with the fine hairs that guard the entrance to the ear canal, helps prevent airborne particles from reaching the inner portions of the ear canal, where they could accumulate or injure the eardrum and interfere with hearing.
This transfer of sound vibrations is possible through a chain of movable small bones, called ossicles, which extend across the middle ear, and their corresponding small muscles. However, in order to set the fluid into motion, greater pressure is required, so that the pressure must be amplified.
The modiolus is shaped like a screw whose threads form a spiral platform that support the cochlea, which is fleshy and unable to support itself. When a taller stereocilium bends away from a shorter one, it pulls on the tip link, so that the ion channel of the short stereocilium is opened. Intense activity in the cochlea nerve fibres from a broad region of the organ of Corti is therefore detected by the brain and interpreted as a loud sound. In humans, the parts of the ear that allow for the sense of equilibrium are the vestibular apparatus (or the vestibule). The tips of the stereocilia and the kinocilium are embedded in a jelly-like membrane called the otholithic membrane.
Any orientation of the head causes a combination of stimulation to the utricles and saccules of both ears. In some individuals, excessive stimulation of the utricle can also produce motion sickness (carsickness, airsickness, seasickness).
Blockage of the duct causes an increase in endolymphatic pressure and swelling of the membranous labyrinth in which the inner ear hair cells are located. Cochlear implants cannot restore normal hearing but they permit recipients to recognise sounds. Because sensorineural damage caused by presbycusis is a gradual process that accompanies old age, many people fail to recognize it and treat it. Birds and many amphibians have the natural ability to recover their hearing by regenerating hair cells, and researchers are currently studying them in hopes of artificially mimicking their regeneration process. Secondly, the sound is less intense when it reaches the second ear, because the head acts as a sound barrier, partially disrupting the spreading of the sound waves. For the membrane to move freely when air strikes it, the resting air pressure on both sides of the tympanic membrane must be equal.
This amplification of the pressure of the airborne sound wave to set up fluid vibrations in the cochlea is related to two mechanisms. Conversely, when the voltage of the hair cells becomes more negative, the hair cells release less neurotransmitter and the firing rate in nerve fibres decreases.
This modification of the basilar membrane is believed to improve and tune the stimulation of the inner hair cells.

The endolymph bathing the stereocilia has a very high concentration of K+ ions, so that when the channel is pulled open, there is a rapid flow of K+ into each hair cell.
The vibration of one region of the basilar membrane causes a wave of vibration to travel down its length and back again. These consist of the three semicircular canals, and the two chambers – the saccule and the utricle.
The overall orientation of the head is interpreted by the brain by comparing the inputs from both organs to each other, and to other input from the eyes and stretch receptors in the neck.
The different orientations of the three ducts cause different ducts to be stimulated, depending on what plane the head is rotating in.
Those hair cells that process high-frequency sounds are the most vulnerable to destruction. Success can range from an ability to hear a phone ringing, to being able to carry on a conversation over the telephone. It is important to realize that untreated hearing loss of any type may lead to severe side effects such as depression and even increase chances of Alzheimer, dementia and heart conditions. They have also recently found that the zebrafish uses hair cells on its body to sense its surroundings, and these work in similar ways to humans’, presenting an opportunity for experimentation to screen helpful chemicals and treatments.
The inner ear also contains the receptors for sound which convert fluid motion into electrical signals known as action potentials that are sent to the brain to enable sound perception. All these cues are integrated by the brain to determine the location of the source of the sound. The outside of the membrane is exposed to atmospheric pressure (pressure of the environment in which we find ourselves) through the auditory tube, so that the cavity in which it is located, called the tympanic cavity, is continuous with the cells in the jaw and thorat area.
Firstly, the surface area of the tympanic membrane is much large than that of the oval window. It is thought that the tympanic reflex is an evolutionary adaptation for protection against loud but slowly building noises such as thunder. The outer hair cells therefore enhance the receptors of the inner hair cells, increasing their sensitivity to sound intensity and rendering them highly discriminatory between various pitches of sound. This is referred to as a standing wave, and is akin to plucking a string at one end, causing a wave vibration (like on a guitar). The otoliths add to the density and inertia of the membrane, aiding in sensing gravity and motion. If we begin to move upwards after being stationary (for example, going upwards in an elevator), the otolithic membrane of the vertical macula sacculi lags briefly behind and pulls down on the hair cells.
Researchers have managed to identify protective chemicals by dyeing the fish’s hair cells, administering the chemicals, then exposing the fish to another chemical known to kill hair cells. The airborne sound waves must therefore be channelled toward and transferred into the inner ear for hearing to occur. Normally, the auditory tube is flattered and closed, but swallowing, yawning and chewing pull the tube open, allowing air to enter or leave the tympanic cavity.
In addition, the lever action of the ossicles greatly increases the force exerted on the oval window. However, because it has a time delay of about 40 ms, it is not quick enough to protect the inner ear from sudden loud noises such as gunshots. When the stereocilium is bent the other way, the channel closes and the cell voltage becomes negative. The peak amplitude of the standing wave is near the top end during low-frequency sounds and near the bottom end during higher-frequency sounds. One is static equilibrium, referring to the ability to detect the direction of the head when the body is not moving. When we stop moving, the otolithic membrane keeps moving for a moment, bending the hair cells upward.
This opening of the auditory tube allows air pressure in the middle ear to equilibrate with atmospheric pressure, so that the pressures on both sides of the tympanic membrane become equal to each other. The extra pressure generated through these mechanisms is sufficient to set the cochlea fluid in motion. Of these, there are about 3500 inner hair cells (IHCs), each with a cluster of 50-60 stereocilia graded from short to tall.
It also does not adequately protect the ears from sustained loud noises such as factory noises or loud music.
When the cell voltage is positive, the inner hair cells release a neurotransmitter that stimulates the sensory nerves at the base of the hair cell. When the brain receives signals mainly from inner hair cells at the top end, it interprets this sound as being low-pitched. The brain therefore receives signals from the macula sacculi, enabling it to interpret vertical acceleration. They also help compensate for the loss in sound energy that naturally occurs when the sound waves pass from air into water by amplifying the sound energy during the process of sound transmission.
Excessive pressure on either side of the tympanic membrane dampens the sense of the hearing because the tympanic membrane cannot vibrate freely. There are another 20 000 outer hair cells (OHCs) that are arranged in three rows opposite the IHCs. These noises can irreversibly damage the stereocilia of the hair cells in the inner ear, leading to hearing loss.
Likewise, when the brain receives signals mainly from inner hair cells at the bottom end, the sound is interpreted as being high-pitched. Acceleration can in turn be divided into linear acceleration, which is a change in velocity (rapidity) in a straight line, and angular acceleration, which is a change in the rate of rotation of the head. In addition to converting sound waves into nerve action potentials, the inner ear is also responsible for the sense of equilibrium, which relates to our general abilities for balance and coordination. When external pressure changes rapidly, for example during air flight, the eardrum can bulge painfully because as the pressure outside the ear changes, the pressure in the middle ear remains unchanged.
Each OHC has about 100 stereocilia with their tips embedded in the tectorial membrane above them. In the reality of everyday life, speech, music and other everyday sounds are not pure tones. The saccule and utricle detect static equilibrium and linear acceleration, while the semicircular canals only detect angular acceleration. These outer hair cells adjust the response of the cochlea to different sound frequencies so as to enable the inner hair cells to function more accurately. Instead, they create complex patterns of vibration in the basilar membrane that have to be decoded and interpreted by the brain. The physiological mechanisms, by which hair cells within the cochlea act to produce hearing, are discussed in more detail below. Middle ear infection is common in children because their auditory tubes are relatively short, compared to adults. This leads to fluid accumulation in the middle ear, which is not only painful but also disrupts the transference of sound across the middle ear. A jelly-like membrane called the cupula extends from the crista ampullaris to the roof of the ampulla. If the infection is left untreated, it can spread from the cells near the jaw, causing meningitis (inflammation of the brain lining). Middle ear infection can also cause the fusion of the ear ossicles, resulting in hearing loss. The endolymph thus pushes against the cupula, causing the stereocilia to bend, stimulating the hair cells. However, after 25-30 seconds of continual rotation, the endolymph catches up with the movement of the duct and stimulation of the hair cell ceases.

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