Question 1
Hollyfield: Regulator of inner ear progenitor fate and outer hair cell function.
Introduction
Located within the mammalian cochlea and critical to hearing function, the organ of Corti is a sensory epithelium, comprised of auditory receptors, called hair cells, and their supporting cells. In avians, hair cells and supporting cells share common progenitors in the auditory epithelia (Fekete et al., 1998; Kirjavainen et al., 2008). During embryonic development it is crucial to have the right number of hair cells and supporting cells from progenitor cells for proper organ function. Loss or even gain of supernumerary hair cells and/or supporting cells can lead to deafness (Chen et al., 2008; Chen and Segil, 1999; Mellado Lagarde et
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Not only can the loss of inner hair cells lead to deafness, but so can the loss of outer hair cells. In rats, loss of 1/3 of OHCs will cause hearing impairment, and 2/3 loss will lead to deafness (Chen et al., 2008) .
Supporting cells: Within the organ of Corti, there are also five different types of supporting cells with distinct morphologies: Hensen’s cells are cuboidal or slightly oblong, inner phalangeal cells and border cells are columnar, and Deiters’ and pillar cells are elongated and have strong cytoskeletons for large structural demands (Wan et al., 2013). Like hair cells, supporting cells are also precisely arranged in the organ of Corti, by rows from the outer edge to the inner edge of the organ in the order of: Hensen’s cells, Deiters’ cells, pillar cells, inner phalangeal cells, and border cells (Wan et al., 2013). One should note that supporting cells do not just take up space in the auditory epithelium. Loss of Deiters’ and pillar cells enviably leads to a loss of OHCs, causing deafness due lack of amplification (Mellado Lagarde et al., 2013). In addition, supporting cells also provide trophic factors, which are vital to the maintenance of spiral ganglion neurons (Monzack and Cunningham, 2013)
Cell cycle exit and p27kip1
To get the right number of hair cells and supporting cells during development,
Anyone of any age who has highly impaired hearing loss or suffers from being deaf could have a cochlear implant. Damage to the inner ear, Aging, prolonged exposure to loud noise and diseases such as rubella (German measles) or mumps may cause wear and tear on the hairs or nerve cells in the cochlea that send sound signals to the brain. When
Deafness can be the result of many different causes such as otitis media (middle ear infections), hereditary disorders, genetic mutations at birth, prenatal exposure to certain diseases such as meningitis, and trauma to the eardrum or auditory nerves. (Better Health Channel, 2013)
(2005) neurofibromatosis type II is a rare condition with an incidence of 1 in 25,000 persons and a penetrance of nearly 100% by age sixty. NFII is an autosomal dominant heritable neoplasia syndrome as defined by Asthagiri et al. (2012). The hallmark of this disorder is the development of bilateral acoustic neuromas, also known as cochleovestibular schwannomas (CVSs), on the auditory nerve. According to previous research, bilateral CVSs are present in 90-95% of NFII patients (Evans, et al., 1992). These non-cancerous tumors are a result of an NFII gene mutation specifically affecting a protein called merlin, also known as schwannomin. This protein acts as a suppressor, keeping cells from growing too rapidly. When the mutation occurs in the gene, it leads to a production of non-functioning merlin protein that cannot regulate growth and division of cells leading to acoustic neuromas. Although it is known how these neuromas form, the way that these neuromas cause hearing loss is not yet fully understood. Asthagiri et al. (2012) stated that “the most frequently cited hypothesis is that the enlarging CVS causes hearing loss through direct compression and stretching of the cochlear nerve.” Neurofibromatosis type II is characterized by bilateral acoustic neuromas, and the surgery to remove these neuromas generally results in severe damage to the auditory nerve causing deafness (Jackson, Mark, Helms, and Behr,
To do this, the researchers exposed a second group of adult quail to the same hearing-damaging sound as the first and then injected them with radiolabeled thymidine. This allowed researchers to use autoradiography that produce low levels of background issues as well as being able to see 10 to 20 grains over red blood cells. The control birds were still given the injections, however, they were not exposed to the sound. The experimental group experienced the same pattern of damage as the birds in the previous experiment and thymidine was seen over hair cells and support cells in the damaged area. There was no thymidine observed outside of the damaged area. The transition zone of the basilar membrane, where tall and short hair cells are integrated, it seemed that the short cells were more often labeled than the tall cells. Tall cells do not lack the afferent auditory-nerve fiber innervation that is seen in short cells making them a more useful candidate for labeling. The researchers failed to identify location and mechanism of the activation of the precursor cells but remained hopeful that there may exist a way to restore inner ear sensory losses that are caused from injury of hair
Most existing research and models of auditory neuropathy has utilised gerbils. At present no robust model of auditory neuropathy in guinea pigs exists; previous guinea pig models have been used but these were not robust and were susceptible to confounding.
First I will explain how hearing loss works, So it may be no surprise that loud sounds can damage hearing, but what actually happens is that the pain is caused by damage to the nerves in your ear. For example, if you hear something really loud close to your ear the nerves get hit by a huge wave of sound that can damage your hearing. Furthermore, there is the question
Melanin is also said to be linked with hearing. Melanocytes are present in the inner ear, the eye, and in the membrane that covers the brain and spinal cord. It has been demonstrated that melanin deposits in these areas are proportional to the amount of melanin found in the skin . These areas of the body, similar to the skin, are exposed to high-energy free radicals that can damage the surrounding cells, and thus causing a lower threshold for hearing.
While sensorineural deafness can be the result of tiny hair cells being damaged, this can also occur when the auditory nerve is damaged (Better Hearing Institute, n.d.). Sensorineural deafness changes the ability of hearing faint sound and reduce the intensity of sound, creating difficulties for the person suffers from it to understand others (hearcom, n.d.). The causes of sensorineural deafness may vary, the exposure to loud noises, aging, medicines, illnesses, head trauma, or malformation in the structure of the inner ear are all potential causes (Better Hearing Institute, n.d.). Genetic also play as a role in the cause of sensorineural deafness. While sensorineural hearing loss is irreversible, researchers have found a way to help the patients to be able to hear better. Through a cochlear implant, an electronic device that replaces the function of the damaged inner ear and provide sound signal to the brain, people who suffer from sensorineural hearing loss would be able to hear (cochlear,
The ear growth is almost linear between four months to eight years old, and after that it is constant until around 70. After age 70,the ear continues to grow.The ear growth is almost linear between four months to eight years old, and after that it is constant until around 70. After age 70,the ear continues to grow .The ear growth is almost linear between four months to eight years old, and after that it is constant until around 70. After age 70,the ear continues to
If you don't protect you hearing your cells will disintegrate and they do not grow back nor heal.
Our ears – including our outer, middle, and inner, are our body’s organ for hearing. The real purpose of our outer ear isn’t to hold our hair back or keep our sunglasses on, but to capture sound vibrations like a cup and direct them through the skull where they are converted into action potentials in a “sensory dendrite” that is connected to the “auditory nerve” (Farabee, 2001). The brain combines the input of our two ears to determine the direction and distance of sounds.
The ear is an extraordinary human organ that many people take for granted until it doesn’t function. It is the only device that allows the human to hear sounds in their environment. The ear is made up of many parts that distinguish various sounds through different means. The ear anatomy and physiology along with how sound waves are transmitted into meaningful sounds will help one understand how hearing loss occurs.
Hearing loss is a drastic change in your everyday life no matter which type it is that you
Noise induced hearing loss affects the hair cells of the cochlea and typically develops over years of exposure to noise (Kirchner et al., 2009). Although noise induced hearing loss typically develops over years, noise trauma occurs after one incidence of excessive noise exposure, such as an explosive blast or fireworks. Due to the nature of noise exposure, a noise induced hearing loss typically occurs bilaterally; however, in certain environments, asymmetrical hearing losses can occur as the result of noise exposure (Bess & Humes, 2009; Kirchner et al., 2012). Currently, there is no treatment for noise induced hearing loss. Nevertheless, hearing loss can easily be prevented by limiting noise levels and time of exposure (Fligor, 2011). Approximately 10 million Americans are currently suffering from noise induced hearing loss and an additional 30 to 50 million Americans are exposed to excessive noise levels each day (Fligor, 2011). In recent decades, noise induced hearing loss has become one of the leading occupational hazards in
The simple answer is yes, for you and for those around you. Hearing loss may cause you to miss words or conversations, and other sounds such as a phone ringing, a doorbell, or a car horn. Missing out on conversations and other sounds can lower a person’s quality of life in many ways. Hearing loss can affect our enjoyment of life, particularly in our relationships with friends, loved ones, and even at our job.