THE EAR is a sensory organ responsible for both hearing and maintenance of balance composed of three...
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THE EARis a sensory organ responsible for both hearing and maintenance of balancecomposed of three sections: the outer, middle and inner ear.
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The Outer Ear:The Pinna: the outer flap that funnels sound towards the auditory canalAuditory Canal: a tube that carries sound towards the eardrum, it contains wax secreting cells; the wax traps dust etc.
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The Middle Ear:Tympanic Membrane (Ear drum):a membrane that closes off entry into the middle ear; vibrates when sound waves reach it.
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Ossicles: three small bones (Hammer, anvil and stirrup) that amplify the sound vibrations from the ear drum and carry them to the oval window.
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Oval Window: a small membrane that seperates the middle from the inner ear. Transmits vibrations from the ossicles to the inner ear.
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Eustachian Tube: a tube that connects the middle ear with the throat; used to equalize pressure between the atmosphere and the middle ear.
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The Inner Ear:Vestibule: contains two small sacs called the Utricle and Saccule, aid in establishing head position. (Static Equilibrium)
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Semicircular Canals: 3 tubes arranged at different angles, filled with a fluid that helps in establishing body position (Dynamic Equilibrium)
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Cochlea: a snail shaped organ containing a fluid and specialized hair cells that move when vibrations from the oval window occur. The hair cells respond differently to sound waves of different frequencies and intensities.
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Auditory Nerve: transmits information to the brain from the inner ear on balance and sound.
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STEPS INVOLVED IN HEARING
sound is a form of energy that travels in wavesit is the movement of these waves that initiates the hearing process:
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1.When sound waves reach your ear; they push against the tympanic membrane causing it to vibrate.2. The vibrations are transferred to the ossicles; which concentrate and amplify the sound.
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3. The vibrations from the last bone, the stirrup, cause the movement of the Oval Window inwards4. The movement of the window initiates movement of a fluid found within the Cochlea.
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5. This fluid movement stimulates the Basilar Membrane of the Organ of Corti; the technical name given to the hearing apparatus in the Cochlea.
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6. Attached to the basilar membrane are Hair Cells that will bend in response to the stimulation.
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7. The bending hair cells stimulate sensory neurons that transmit the information through the Auditory Nerve to the Temporal Lobe of the Cerebrum.
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Different Hair cells have different threshold levels that will depolarize depending on the frequency or intensity of the sound.
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Maintenance of Balance
two components to balance:
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1. Static Equilibrium:balance involving the position or movement of the head.head position is determined by the two fluid filled sacs (Utricle and Saccule) found in the vestibule.
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in the fluid are suspended particles called OTOLITHS.when the head moves, the otoliths moves; this causes movement of the hair cells that line the interior of the sacs
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the hair cells stimulate sensory neurons that carry information to the brain, through the auditory nerve, regarding head position
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2. Dynamic Equilibrium
balance involving the movement of the bodyinvolves the movement of the fluid found in the SEMICIRCULAR CANALS
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when we move, the fluid moves causing the movement of hair cells that line the canals.
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when the hair cells move, they stimulate sensory neurons which will carry information regarding body position to the brain through the auditory nerve.