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Three types of hearing loss
- -Sensorineural hearing loss
- -Conductive hearing loss
- -Mixed hearing loss
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Sound
- -Sound cannot travel through a vacuum. It must travel through something – air, water,or even bone.
- -There are a few major aspects of sound: intensity (loudness) which is measured in decibels, This has a profound effect on hearing, as listening to loud sounds for prolonged periods can have a permanent impact of hearing – and not in a good way.
- -Two other aspects of sound are frequency and amplitude. These two terms deal with the waves that sound produces. -Frequency is the number of sound waves that cross a point in a certain amount of times. Sounds with the highest frequency produce more waves to pass a point, and sound higher in pitch. Pitch is the way we perceive frequency.
- -Amplitude deals with how high the waves are, which is what we perceive as loudness.
- -So, pitch is caused by how close together waves are (frequency) while intensity is determined by how tall the waves are (amplitude).
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Detecting sound
- -Pitch is caused by how close together waves are (frequency) while intensity is determined by how tall the waves are (amplitude).
- -This influences hearing in a couple ways. The human ears are designed to detect sounds in a set range of pitches and frequencies. Detecting this sound involves the ear.
- -Sound is collected in the outer shell of the ear, called the pinna. This sound travels in air through the auditory canal until it reaches the tympanic membrane (the eardrum). Sound causes the tympanic membrane to vibrate. When the tympanic membrane vibrates and converts sound to mechanical waves, causing the ossicles (earbones) to vibrate. The malleus vibrates, causing the incus to vibrate, causing the stapes to vibrate. The stapes hits the oval window as it vibrates, pushing on the fluid inside the cochlea to vibrate in the form of a fluid wave. This vibration travels through the cochlea, stimulating the sensory hair cells, which are incredibly sensitive. Their stimulation results in a signal passing to the cochlear nerve, which sends a signal to the brain so sounds can be interpreted.
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Ear funcitons
- -Hearing
- -Balance
- -Pressure
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Balance
Involves the vestibule of the ear, which houses the semicircular canals. This is a set of three tubes that give you the ability to sense up, down, and sideways. Body position shifts fluids around in this area, allowing you to sense your position in space when the signals produced by the nerves in the canal send signals via the vestibular nerve to the brain.
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Pressure
-Also in the ear is the eustacian tube, which is there to maintain pressure within the inside and outside of the ear. If pressure is different, sound doesn’t travel right!
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Conductive hearing loss
- -Caused by damage to the wave-carrying portions of the ear: the pinna, the auditory canal, the tympanic membrane, or the ossicles.
- -This type of hearing loss usually involves a reduction in sound level or the ability to hear faint sounds.
- -This type of hearing loss can often be corrected medically or surgically.
- -It can be caused by a loss of the outer ear, damage to the tympanic membrane, or damage to the ossicles.
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Sensorineural hearing loss
- -Rhere is damage to the cochlea (inner ear) or the auditory nerve.
- -In many cases, it cannot be corrected.
- -It can be caused by repeated exposure to loud noises, an extremely loud noise one time, or aging of the cochlea.
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Mixed Hearing loss
-Mixed hearing loss is a combination of both
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Hearing aid
- -Treatment for all cases
- -Amplify sounds, making them louder to the person with a device in their ear and allowing them to hear better.
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Cochlear Implants
- -Option for Sensorineural Hearing loss
- -This is a small device inserted surgically in two phases, with a wire placed in the cochlea to do the job of hair cells and direct sound waves from the fluid in the cochlea to the auditory nerve, and with an external implant (on the head) to pick up sounds from around the patient.
- -Because this procedure is very expensive, may result in complete hearing loss, and is offensive to the deaf community as an infringement on their lifestyle, it remains somewhat controversial.
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Hearing Loss Tests
- -Rinne Test
- -Speech in noise test
- -Audiograms
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Rinne Test
- -The Rinne test involves using a timer and a tuning fork to determine the difference between conductive and sensorineural hearing.
- -Sensorineural hearing is tested by placing the handle of a tuning fork that has been hit on a table and is humming against the mastoid process on the skull and listening until the sound goes away while timing the length of time the patient can hear. When the sound is no longer heard, with no delay, the tuning fork is flipped and the pronged end is placed in front of the ear, with the patient listening again.
- -Air conduction (conductive hearing) is checked in this way, with the tester then noting the time elapsed. If hearing is normal, the air conduction will be heard twice as long as bone conduction. If there is conductive hearing loss, bone conduction is heard longer or as long as air conduction.
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Speech in noise test
- -Can be done for some types of sensorineural hearing loss.
- -This involves listening to speech with a background static of varying types and determining how well the patient is able to detect actual speech under those circumstances.
- -If there is sensorineural hearing loss, hearing the speech will be incredibly difficult or not possible.
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Audiograms
- -Detect both sensorineural and conductive hearing loss.
- -Audiograms are made during a pure tone test. This involves using an audiometer to measure hearing sensitivity. The test will begin by playing a series of beeps or tones at a distinct frequency. Every time the subject hears the beep, they raise a finger or push a button or raise their hand. The tone will continue to get softer and softer until it can no longer be heard – determining the threshold for the patient for a certain frequency. The test is then repeated at other frequencies between 250 and 8000 Hz. An audiogram records thresholds, which can be used to detect where hearing loss exists at different frequencies. The thresholds are recorded on a graph, called an audiogram, with the frequencies on the x-axis and the hearing thresholds in decibels on the y-axis. The thresholds for the right ear are represented with a red circle and the thresholds for the left ear are represented with a blue ‘X.’ The following diagram is an example of a blank audiogram.The Xs and Os are connected with lines to help keep track of the hearing levels across the different pitches. Hearing levels are often described in a progression of loss: normal hearing, mild hearing loss, moderate hearing loss, moderately severe hearing loss, severe hearing loss, and profound hearing loss. The following chart shows the ranges for each type of hearing level.
- Normal Hearing 0-20 dB
- Mild Hearing Loss 21-40 dB
- Moderate Hearing Loss 41-55 dB
- Moderate to Severe Hearing Loss 56-70 dB
- Severe Hearing Loss 71-90 dB
- Profound Hearing Loss >90 dB
- -Conductive hearing loss can also be represented in an audiogram. The air conduction levels are represented as Xs and Os and the bone conduction levels are represented as < and >. Because conductive hearing loss is due to problems with the middle ear, hearing levels are better with bone conduction than with air conduction. Conductive hearing loss is therefore represented when bone conduction is at least 10 decibels better than air conduction, after it has been determined with a version of the Rinne test.
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Vaccination
-An injection of dead, weakened, or modified pathogens into the body. Their presence in the body activates the immune system, which responds to the substances within the vaccine the same way it responds to any other infection: by activating lymphocytes, producing antibodies, and then remembering that disease for a very long time so you don’t get it again. Antigens in the material contained in the vaccine cause the body to produce antibodies. A specialized type of lymphocyte referred to as a memory cell will remain long after the “infection” is cleared out, and will be able to rapidly produce antibodies when you are exposed to the true infection, thus keeping you from ever getting sick. Vaccinations have been used to reduce the incidence of several types of disease. It has eliminated smallpox and polio, in this country and many others; it keeps us from getting the flu; it is even used to protect us from certain types of cancer, such as HPV.
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Six Methods of Vaccinations
- -Similar-Pathogen
- -Attenuated Virus
- -Killed Vaccine
- -Toxoid Vaccine
- -Subunit Vaccine
- -Naked-DNA Vaccine
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Similar Pathogen Vaccine
Is used to make a vaccination for polio. Here, you find a virus similar to the one you want to protect against (as cowpox is similar to smallpox), isolate the virus, and inject it “live” into the person being inoculated. Smallpox and cowpox are similar enough that protection against one provides protection against the other – they are similar pathogens!
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Attenuated Virus
Protect against the measles virus. This is also a live vaccine. It involves altering the virus enough that it i s weakened in the human body. In the case of measles, the virus is adapted to grow in cold environments. The human body is warm enough that cold-loving viruses don’t do well, so the body has time to make antibodies before an infection sets in. After antibodies are present in the body, you are protected from the normal measles as well as the weakened version.
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Killed Vaccine
what we use to protect against polio. Here – you guessed it – the virus is killed with heat, radiation, or some other means, then injected dead into your body. The dead virus produces a weak response in the body – not enough for true immunity to set in, which is why boosters are often required.
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Toxoid Vaccine
A Toxoid vaccine is created for pathogens like tetanus. Here, the goal is to expose the body to the toxins a pathogen produces, rather than to the pathogen itself. Tetanus is caused by toxins produced by the bacteria Clostridium tetani. Toxins are extracted from the pathogenic organism (the bacteria in this case) and are neutralized so the body isn’t harmed by them. Neutralization can involve chemicals like formaldehyde or aluminum salts. After neutralization, you are injected with the toxin, and the body produces a response. Like with dead viruses, boosters are also required. A subunit vaccine is made for hepatitis B
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Subunit Vaccine
A subunit vaccine consists of nothing more than a portion of a pathogen - a chunk. A specific “chunk” of virus is chosen for vaccination, and the body recognizes that “chunk” on a pathogen when it encounters it.
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Naked-DNA Vaccine
Currently being developed to use in an HIV vaccine. Here, a single gene (which will produce a protein) is selected for vaccination .This gene is amplified and placed into a vector of double-stranded DNA. This DNA is injected into a bacteria, the bacteria grow and are lysed, and the DNA is extracted for injection into the human.
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How recombinant DNA technology is being used to create vaccinations
Recombinant DNA technology involves modifying DNA by adding or removing genes, placing this modified DNA into an organism, and letting that organism replicate. It begins by selection of a gene of interest. This gene is removed from the organism it belongs to by isolating its DNA, then using restriction enzymes to “cut out” that particular section of DNA, which is then amplified (copies are made). The genes are then ligated into double-stranded DNA. Remember that to ligate it is to seal it in, as though it had been glued in place and is now a permanent part of the DNA. This DNA, often double-stranded, circular, and referred to as a plasmid, is pretty useless outside of a living cell. To get beyond that, the DNA is put into a cell using a chemical or electrical shock that makes the bacteria porous enough for the plasmid to enter. Heat shock is then used to seal the cell up again, with the plasmid inside. Once that plasmid is inside a bacterium, the bacteria produces more of that plasmid, incorporating that DNA and making copies of it before the cell divides. Soon, colonies of this modified bacteria live, containing the recombinant DNA we wanted. This DNA can be extracted from the bacteria after they have been killed, and used for the purpose of vaccination, with the DNA injected into the person who needs the vaccine.
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Epidemiologist
- -Everything we have discussed: studying symptoms of disease, detecting disease, making diagnoses, administering treatments, studying the after-effects, and finding ways to prevent diseases from happening all together, are the jobs of an epidemiologist.
- -Epidemiology is the study of disease, and epidemiologists are dedicated medical professionals at the heart of the public health field, monitor the health of populations and search for patterns in disease. They may assist in outbreak investigations or they may examine lifestyle factors and their relationship to chronic illnesses such as heart disease, diabetes, and cancer. Whether in the field, in a lab, or in an office, epidemiologists play a crucial role in maintaining human health.
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