Normal human body function is partly determined by the five common senses: sight, smell, hearing, touch, and taste. Proper function is when the senses can comfortably detect, interpret and respond to information collected from the surrounding. The organs that perform the above tasks are known as sensory organs, including eyes for sight, the tongue for taste, nose for the smell, ears for sound, and the skin for touch. The five sensory organs work hand in hand in sending the information collected to the brain via the nervous system. The brain then sends the response required to the vital organ for the cause of action. For example, when crossing the road and a car hoots, the ear collects the information, sends it to the brain, where the brain sends a response to the legs, which is to either stop or move faster to avoid being hit by the car. Normal hearing is one of the most important body functions as its damage affects other body functions, such as speaking and properly executing daily tasks.
How Normal Hearing Occurs
The ear portion includes the auricle or the pinna, and the ear canal is referred to as the outer ear. The pinna is a concave structure cartilaginously purposed for collecting and directing waves of sound traveling in the surroundings and funnels through the external auditory meatus. Griggs (2016) stated that the auditory canal has a diameter of about 0.25 inches and has a length of 1.25 inches. It directs the sound waves that are airborne towards the eardrum or the tympanic membrane. The external auditory canal reverberates sound waves where tone loudness is increased in a range of 3000-4000 Hz, as noted by Griggs (2016). Additionally, the auditory meatus maintains proper humidity and temperature conditions essential to preserve the eardrum elasticity. Through earwax (cerumen) production and the growth of tiny hairs in the canal, the tympanic is protected from damage preventing hearing complications.
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The middle ear comprises the ear cavity, which shelters the anvil, stirrup, and hammer (the ossicular chain. The eardrum or tympanic membrane functions as a separator of the outer and the middle ear. It has three living tissues, which are gray-pink colored. With the sound waves hit, the tympanic membrane vibrates back and forth as it is extremely sensitive to sound waves. Griggs (2016) notes that the cavity is positioned in the mustoidal of the temporal bone. It extends to the inner ear from the tympanic membrane. The middle ear cavity is an extension via the Eustachian tube of the nasopharynx. Ventilation and air pressure equalization of the middle ear task is served by the Eustachian tube. Sound transmission to the tympanic membrane is best when air pressure between the outer and middle ear is equalized. When there is an imbalance of air pressure, the tympanic membrane is forced inwards or outwards, leading to the eardrum's reduced sound transmission ability.
The ossicular chain comprises tiny bones; incus, stapes, and malleus, where stapes is located in the oval window, malleus attached to the eardrum and incus between stapes and malleus. The transmission of sound waves into the inner ear is through the ossicular chain from the middle ear. The signal is amplified to about 25 volumes, where the signal is transported to the inner ear from the eardrum (Goldstein, 2017). Vibrations are produced as a result of sound waves in the tympanic membrane, where a chain of reactions is created from the vibrations which move the incus, stapes, and malleus. These are three-minute bones located in the middle ear and also the smallest bones in a human body. Oval window vibrations are created as a result of stapes movement. Two small muscles, tensor tympani and stapedius muscles, are attached to the ossicular chain. The two muscles contract to protect the inner ear through sound transmission intensity reduction from vocal transmissions and external sounds.
In the inner ear, the most important sensory organ for hearing, the cochlea is located. The balance system or vestibular is also comprised of the inner ear. The vestibular apparatus is comprised in part of 3 canals that are semicircular within the inner ear (Goldstein, 2017). It assists in balance maintenance regardless of gravity or head position. The cochlea is the hearing part within the inner ear containing receptor cells that aid in hearing with spiral or snail shape. It comprises three fluid-filled chambers. Hearing receptors are minute hair cells lining the basilar membrane, a membrane extension through the cochlea's length. As compared to cones and rods in the eyes, hair cells in-ears are less, with approximately 16,000 hair cells for each ear, as stated by Griggs (2016).
Fluid displacement within the cochlea is a result of oval window vibrations. Displacement of cochlea fluid leads to hair cell movement resulting from basilar membrane movement caused by the vibrations. Movement patterns of the minute hair cells purposes coding of the auditory message. Hair cell's motion is translated into neural impulses. The neural impulses are then passed to the auditory nerve cells, where the information is then transported to the thalamus (Goldstein, 2017). The information is then directed to the temporal lobes containing the primary auditory cortex. Pitch is the sound quality described as low or high determined by sound wave frequency. Griggs (2016) indicates that humans perceive frequencies of sound waves from approximately 20-20,000 Hz. The place theory assumes that along the basilar membrane, a particular part will respond maximally to precise frequencies starting from the oval window. The frequency theory assumes that the hair cells' firing rate imitates the frequency of the incoming information. It shows how high and low pitches are perceived.
Causes of Presbycusis
Presbycusis is a gradual loss of hearing occurring mostly in aging individuals. Presbycusis is mostly associated with high-pitched sounds. Changes in an individual's inner ear as they age lead to hearing loss as a result of disorders in the auditory nerve. Exposure to daily construction works, noisy offices, loud traffic, and loud music gradually damage the auditory nerve (Griggs, 2016). Abnormalities of the outer/middle ear, such as functional deficiency of the eardrum or the three bones, can also lead to hearing loss. Additionally, presbycusis can also be caused by blood supply changes in the ear resulting from heart complications ( Cheslock, 2020) . Aging individuals develop heart diseases and are under medications whose side effects can also affect hearing ability.
Having Presbycusis
As a result of hearing loss, an individual will not hear clearly, especially when low tones are used. An individual suffering from hearing loss will most likely wrongly respond to conversations with colleagues or family since they might have missed part of what was said. People who have hearing loss will separate themselves from others since they cannot properly communicate, leading to loneliness and depression ( Cheslock, 2020) . Socializing becomes a problem as conversing becomes a problem due to the less able to hear. Activities such as sporting and dancing, which require communication, become difficult to participate. People suffering from presbycusis suffer fewer job and education opportunities as they are unable to communicate. When a person suffering from hearing loss is doing a presentation at a workplace, they will not properly answer the audience's questions.
Conclusion
Normal functioning of the body, social life, and execution of an individual's daily tasks is partly dependent on their hearing ability. Hearing is very critical as it affects many aspects of the daily functions of a person. How individuals communicate solely helps them express themselves at work, at school, or with family and friends. When all parts of an ear function properly, an individual enjoys a normal life without communication barriers. The ear's health should be loosely monitored to maintain its best functioning and for long. Individuals should be aware of factors that can lead to hearing loss, such as noise at work, loud music, etc. Putting on earmuff and earplugs can prevent ear damage as a result of high-frequency sound waves. Hearing professionals should be regularly visited for ear checkups, especially for aging individuals and those who regularly get exposed to high sound waves.
References
Cheslock, M., & De Jesus, O. (2020). Presbycusis. StatPearls [Internet] .
Griggs, R. A. (2016). Psychology: A concise introduction (5th ed.). New York, NY: Worth
Publishers.
https://3lib.net/book/3593702/e26962 Goldstein, E. B. & Brockmole, J. R. (2017). Sensation and perception (10th ed.). Boston, MA: Cengage.
