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To distinguish between the two types of deafness To know the proper method of performing the Rinne and Weber tests
In doing the experiment there are two tests that we shouldperform. First is the Rinne test. From our group we chose therepresentative to whom we would perform the experiment.One ear of the subject was plugged. On the heel of the hand, atuning fork was set in motion by striking it. At the level of theupper portion of the unplugged ear canal, the stem of thetuning fork was placed on the mastoid processes. When thesound from the vibrating fork disappears, the subject wasasked to make a signal. Then, place the line of the fork in frontof the unplugged ear at a distance of 3 to 6 inches. Whetherthe subject hears any sound or not indicate it. The procedurewas repeated on the other ear.
For the next test which is the Weber’s test,another member of the group was selected tobe the subject. On the heel of the hand, thetuning fork was strike. On the forehead of thesubject the stem of the tuning fork wasplaced. We asked the subject to compare thesounds that was heard in each ear. Weindicate whether the sound was heardequally or not.
Outer ear – pinna, external auditory canal Middle ear – tympanic membrane, three ossicles and the Eustachian tube Inner ear – cochlea, semicircular canals, nerves * All three parts are involved in hearing while for vestibular functions, the inner ear is the only one involved.
1. Pinna/auricle/earlobe – funnels the sound waves into the ear2. External auditory canal – passageway of sound to the middle ear; lined with hair3. Eardrum/tympanic membrane – transmits sound from the outer ear to the ossicles4. Malleus, incus, stapes – three small bones of the ear5. Eustachian tube – equalizes the pressure in the middle ear and the throat
6. Cochlea – organ of hearing; Lt. for “snail shell”; has Organ of Corti ▪ Scala tympani ▪ Scala vestibuli ▪ Scala media7. Semicircular canals – three (anterior, lateral, posterior); for balance8. Vestibule – central part of the bony labyrinth
Malleus faceplate of stapes (3/4 of theamplitude of movement)Surface area of tympanic mem. : 55 sq. mm.Surface area of stapes: 3.2 sq. mm.22 TIMES MORE PRESSURE ON THE FLUID.
Reduces the intensity of the sound by as much as 30-40 decibels Latent period of 40-80 ms Stapedius – pulls stapes outward Tensor tympani muscles – pulls malleus inward Reduce ossicular conduction Protect cochlea, mask low-frequency sounds in the env., and dec. sensitivity to own voice
Sound energy Mechanical energy Hydraulic movements Chemical energy Electrical energy BRAINMechanical Energy: Vibrations of the eardrum lever-like action of the ossiclesHydraulic Energy: Faceplate and oval window Organ of Corti
Scala tympani – perilymph Scala vestibuli – perilymph Scala media – endolymph Reissner’s membrane (vestibular membrane) – s. vestibuli from s. media Basilar membrane – s. media from s. tympani; modiolus (high freq. at oval window, low freq. near the apex) Organ of Corti – contains a series of electromechanichally sensitive cells, hair cells; transduces pressure waves to action potentials
Tympanic membrane>malleus>incus>s tapes>oval window>scala vestibuli>scala tympani>basilar membrane>hair cells receptorsImpedance matching-ossicular system reduce distance but increase the force of movement by 1.3X about 22X pressure exerted in the fluid.
The movement of the basilar membrane cause the hair cell stereocilia to bend. Stereocilia is directionally sensitive: Upward towards scala vestibuli: hair cells depolarized Down towards the scala tympani:hair cell hyperpolarized
From the bending of the stereocilia opens ionic channel>influx of K. Membrane potential decreased to -50mV from 60mV(resting membrane potential) Opens the Ca2+ channel
1st order neuron: located in SPIRAL GANGLION 2nd order neuron: dorsal and ventral cochlear nuclei[form 3 groups of acoustic striae(lateral lemniscus): ventral striae-most prominent forms trapeziod body] 3rd order: superior olives nucleus 4th order neuron: medial geniculate nucleus
Area 41 and 42>>Primary auditory area-anterior part: low frequencyPosterior part:reception of high frequency Area 22>>Secondary auditory areaInterpretation of sound and for association of auditory inputs.
Superior olivary nucleus- fibers joins ipsi and contralateral lateral lemnisci. Localization of sound in space Nucleus of lateral lamniscus- send axons on both epsi and contralateral lemnisci. Aids in bilateralism by sending axon to the contralateral side.
Whispered Voice Test Ticking Watch Test Weber Test Rinne Test Schwabach Test
Conductive hearing loss Neural hearing loss (Nerve deafness) Mixed hearing loss
sound vibrations dont go from the air around a person to the moving bones of the inner ear sounds are heard, but they are weak, muffled, and distorted
auditory nerve, which goes from the inner ear to the brain, fails to carry the sound information to the brain cause a loss of loudness or a loss of clarity in sounds. Mixed hearing loss combination of conductive and neural hearing losses
Heredity Diseases of the Ear Injuries of the Ear
born deaf cause is unknown something that happened to the mother during her pregnancy
Ear infections cause fluid or mucus to build up inside the ear fluids drain out of the ear or are absorbed into the body Otosclerosis common cause of hearing loss hereditary disease in which portions of the middle ear or inner ear develop growths like bony sponges can be in the middle ear, the inner ear, or both places
Meningitis inflammation of the membrane(called the meninges) that surrounds the brain and the spinal column
Punctures of the Eardrum a hole in the eardrum, which could be caused by either injury or disease Nerve Damage result of nerve damage is that the electrical signals of sounds do not get transmitted from the ear to the brain
Loud Noises common cause of deafness is repeated or long- term exposure to loud noises often cause moderate to severe hearing loss.
sound-amplifying devices to aid people who have a hearing impairment.
help you converse in noisy environments allows sound coming from a specific direction to be amplified to a greater level sound coming from in front of you is amplified to a greater level than sound from behind you
allows you to switch from the normal microphone setting to a "T-coil" setting to hear better on the telephone. Direct audio input allows you to plug in a remote microphone or an FM assistive listening system or connect to other devices
helps suppress squeals when a hearing aid gets too close to the phone or has a loose- fitting earmold
Behind-the-ear (BTE) aids "Mini" BTE (or "on-the-ear") aids In-the-ear (ITE) aids In-the-canal (ITC) aids and completely-in- the-canal (CIC) aids
contained in a small plastic case that rests behind the ear case is connected to an earmold or an earpiece by a piece of clear tubing often chosen for young children because it can accommodate various earmold types can help with all types of hearing loss, from mild to profound Sound travels from the earmold into the ear
fits behind/on the ear, but is smaller very thin, almost invisible tube is used to connect the aid to the ear canal allow not only reduced occlusion or "plugged up" sensations in the ear canal mild hearing loss who can still hear low- and mid-frequency sounds
contained in a shell that fills in the outer part of the ear mild to severe hearing loss it can accommodate directional microphones and other added features
contained in tiny cases that fit partly or completely into the ear canal smallest hearing aids available In-the-canal (ITC) aids works only for mild to moderate hearing loss users sometimes experience feedback noise with this type of hearing aid because the microphone and receiver sit close together
Completely-in-the-canal (CIC) appropriate for mild to moderate hearing loss, and its even smaller than the ITC hearing aid barely visible
Analog hearing aids Digital hearing aids
aids amplify sounds amplify all sounds equally Digital hearing aids contain a computer chip analyzes the sound based on the persons hearing loss and listening situation adjusts for feedback
Young, P.A., Young,P.H.,&Tolbert,D. (2008). Basic clinical neuroscience. (2 nd ed.). USA:Lippincott Wlliams and Wilkins Hall, J.E., (2010). Guyton and Hall Textbook of Medical Physiology. (12th ed.). Ganong,William F.(2006).Review of Medical Physiology 23rd edition.San Francisco,California:Lange Medical Publications