Chapter 9 Study Questions Flashcards
(33 cards)
The auditory system is highly sensitive and can rapidly detect changes in _______ , measured in decibels (dB), and in _______ , measured in hertz (Hz). The decibel scale is _______ and is calculated from the ratio of the sound pressure level of the source being measured (say, a jetliner) to a reference level. This reference level is the human threshold intensity for hearing a _______ -Hz tone and is calculated to be 0.0002 _______ in amplitude.
intensity; frequency; logarithmic; ONE HUNDRED; dyn/cm2
The external ear consists of the fleshy part on the outside of the head, called the , plus the that leads to the ear drum.
pinna; CANAL
The middle ear starts at the eardrum, which is formally known as the . This is connected to the inner ear by a series of minuscule bones, the , the , and the , which are known collectively as the .
tympanic membrane; MALLEUS; INCUS; stapes; ossicles
The ossicles act by focusing the energy collected on the large tympanic membrane onto the small window, which results in . The middle ear also contains two tiny muscles called the and the , which act like a gain (or “volume”) control.
oval; AMPLIFICATION; TENSOR TYMPANI; STAPEDIUS
In the operation of this muscular volume control, the muscles, when contracted, prevent the from moving as much as they normally would, thereby the amount of energy transmitted to the inner ear and, in essence, “turning down the volume.” This system is activated within milliseconds when a sound is encountered, either in the environment or originating within the body. In the case of vocalization, the system activates itself just you start to speak, which is the reason you do not experience your own voice as deafeningly loud.
OSSICLES; reducing; loud; before
The auditory portion of the inner ear is the , which is just in diameter and resembles a snail. It is made up of three canals running along its length—the canal, the canal, and the middle canal—and is filled with fluid.
cochlea; 4mm; TYMPANIC; vestibular
When the ossicles push on the window, vibrations are transmitted to the fluid filling the cochlea, which in turn causes the membrane to vibrate. This membrane is five times wider at its than at its . On top of the membrane is the organ of , which contains a framework of supporting cells plus the main sensory cells: the cells (humans have about of these) and the cells (humans have about of these).
OVAL; BASILAR; apex; base; Corti; INNER HAIR; “3500”; OUTER HAIR; “12,000”
From the tops of the hair cells protrude tiny stiff hairs called that contact the membrane, which lies over the organ of Corti.
STEREOCILIA; TECTORIAL
The basilar membrane “encodes” the frequency of the stimulus as a function of its shape. When the transmit vibrations to the oval window, this energy is transmitted to the fluid filling the inner ear and causes the basilar membrane to begin vibrating as well. Which portion of the basilar membrane shows the greatest amplitude depends on the of the sound (a process resembling “sympathetic vibration”). Because the basilar membrane is wedge shaped, it encodes frequency along its . High frequencies preferentially affect the end of the basilar membrane (the base), whereas low frequencies have the greatest affect where the membrane is widest (the ).
j
Movement of the basilar membrane, induced by vibrations in the cochlear fluid, causes the stereocilia of the hair cells to . Very small movements of the stereocilia produce rapid changes in the ion of the stereocilia. These changes appear to be the result of the action of , which are mechanical tethers between adjacent stereocilia.
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When the stereocilium sways over, the tip link pulls open its ion channel(s), causing an extremely rapid . When the stereocilium sways back upright, the ion channel snaps shut again. The whole process takes a fraction of a . The depolarization leads to an influx of ions at the base of the hair cell, resulting in the release of —most likely .
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After leaving the cochlea, auditory information is “sharpened” in the nucleus and auditory by neurons that are excited by certain frequencies but by neighboring frequencies.
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The complex is the first level that receives input from both ears. This is important for interaction (that is, stereo), which allows for the localization of sound sources.
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organization is the term used to describe the maintenance of an orderly arrangement according to within the auditory projections, as revealed by studies employing the uptake of to reveal brain areas selectively activated by exposure to particular frequencies. Studies of human subjects using PET and fMRI show that pure tones chiefly activate the cortex, but that activates other cortical regions as well, and that the same regions are activated when subjects try to .
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The frequencies to which humans are sensitive range from about Hz to as much as Hz. Up to 2000 Hz, we can discriminate differences of as little as Hz between tones, although this frequency difference is larger above 2000 Hz.
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One theory of pitch perception is called the place coding. “Place” refers to the location on the that is particularly affected by the sound. Each part of this structure responds preferentially to a particular . In this schema, if the brain knows the place on the where a sound has its greatest effect, it also knows the sound’s .
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An alternative theory of pitch perception, called the coding, argues that the frequency of a sound is directly encoded in the pattern of . Contemporary views of pitch perception incorporate both theories: coding is especially effective for frequencies, whereas coding is especially effective at frequencies.
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Binaural processing of sounds may occur at various brainstem locations, including the superior and also at the level of the inferior ; neurons are thought to perform these comparisons.
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Lesions of the auditory cortex do not abolish the ability to discriminate between different tones. Instead, such lesions selectively impair the perception of sounds, such as species-specific , or patterns of sounds.
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Recent evidence suggests that spatial of sounds is dependent on a stream of auditory processing involving the parietal lobe, whereas the analysis of the composition of sounds is dependent on a stream of processing involving the lobe.
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Evidence concerning early exposure to music suggests that early experience shapes auditory abilities. In imaging studies, musical stimuli such as piano notes (but not ) evoked responses in the brains of than in nonmusicians; more important, the degree of this response in was correlated with the at which musical training began. This suggests that exposure to musical training alters brain auditory responsiveness later in life.
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Animal studies demonstrate that the auditory cortex is organized and can be altered by . Human newborns have diverse hearing abilities, but as they mature, they become particularly adept at discriminating sounds in whatever they hear.
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What are the three major forms of deafness?
deafness involves problems with the or ear that prevent transmission of vibratory stimuli to the inner ear.
deafness involves disorders of the or eighth cranial nerve that interfere with the and of auditory information to the brain.
deafness involves disorders of the auditory systems of the brain, with highly variable symptoms.
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Hearing may be at least partially restored in individuals who are profoundly deaf through the use of implants, which, in the case of deafness, bypass the damaged to stimulate the directly. Although present implants are limited to a range of about 32 different frequencies, such devices have been shown to aid in the development of . Such stimulation dramatically increases the metabolic activity of the auditory cortex, indicating that it is activating the cortex, and outcomes are especially good for patients who are .
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