Chapter 9 Study Questions

Question 1

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.

Answer 1

intensity; frequency; logarithmic; ONE HUNDRED; dyn/cm2

Question 2

The external ear consists of the fleshy part on the outside of the head, called the , plus the that leads to the ear drum.

Answer 2

pinna; CANAL

Question 3

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 .

Answer 3

tympanic membrane; MALLEUS; INCUS; stapes; ossicles

Question 4

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.

Answer 4

oval; AMPLIFICATION; TENSOR TYMPANI; STAPEDIUS

Question 5

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.

Answer 5

OSSICLES; reducing; loud; before

Question 6

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.

Answer 6

cochlea; 4mm; TYMPANIC; vestibular

Question 7

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).

Answer 7

OVAL; BASILAR; apex; base; Corti; INNER HAIR; “3500”; OUTER HAIR; “12,000”

Question 8

From the tops of the hair cells protrude tiny stiff hairs called that contact the membrane, which lies over the organ of Corti.

Answer 8

STEREOCILIA; TECTORIAL

Question 9

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 ).

Answer 9

j

Question 10

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.

Answer 10

1

Question 11

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 .

Answer 11

1

Question 12

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.

Answer 12

1

Question 13

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.

Answer 13

1

Question 14

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 .

Answer 14

1

Question 15

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.

Answer 15

1

Question 16

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 .

Answer 16

1

Question 17

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.

Answer 17

1

Question 18

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.

Answer 18

1

Question 19

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.

Answer 19

1

Question 20

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.

Answer 20

1

Question 21

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.

Answer 21

1

Question 22

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.

Answer 22

1

Question 23

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.

Answer 23

1

Question 24

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 .

Answer 24

1

Question 25

The vestibular system detects the force of on the body and the of the head in three dimensions. This system consists of three oriented in each of the planes of three-dimensional space, each of which has a swelling called an at its base and which all join together at a structure called the . Below this lies the .

Answer 25

1

Question 26

Acceleration in any of the three planes causes stimulation of the cells of the corresponding semicircular canal; these cells are located in the , which lies at the junction between each canal and the . The utricle and saccule, in contrast, detect the position of the head. In each case, the cilia of the hair cells are inserted into a gelatinous mass, and small particles called serve to increase the response of the receptor cells to movement. Afferent fibers arising from the of the hair cells lead to the .

Answer 26

1

Question 27

Information derived from the vestibular system is used constantly in controlling movements of the body; this information travels in the vestibular portion of the cranial nerve, synapsing on cells in nuclei of the brainstem called (not surprisingly) the nuclei. Some fibers of the vestibular projection bypass these nuclei and connect directly to the . This makes sense, given the importance of this structure for control.

Answer 27

1

Question 28

Pilots of airplanes can succumb to what is known as the illusion due to an internal misinterpretation of head angle and acceleration.

Answer 28

1

Question 29

Sensory theory argues that motion sickness arises from a mismatch between and inputs. It has been argued that such a mismatch simulates the effects of (e.g., dizziness, weaving) and that the reaction is an adaptation that evolved to rid the body of possible toxins.

Answer 29

1

Question 30

The basic tastes provide biologically important initial information about foods: foods typically contain energy, and foods are important for homeostasis, tastes usually signify the presence of toxins, and which is a meaty or savory taste found in gravy or soy sauce. Unlike most other mammals, cats are insensitive to tastes, and human newborns appear to be relatively insensitive to tastes, although other aspects of taste are well developed at birth.

Answer 30

1

Question 31

Contrary to popular belief, the bumps on your tongue are not taste buds, but rather . Taste buds are located within the and consist of a cluster of 50 to 150 cells from which protrude fine that emerge to the surface of the tongue through the pore. Many of the cells that make up the taste bud sense tastants, but some are receptors and others respond to . Taste cells live only 10 to 14 days and are constantly being .

Answer 31

1

Question 32

Table on the three kinds of papillae found on the tongue.
Type	Location
papillae…..	 of the tongue
Foliate papillae…..	 of the tongue
papillae…..	 of the tongue

Answer 32

1

Question 33

Table describing the detection of the five basic tastes.

Answer 33

1