Please read the chapter assigned for this week.
(Reading Schedule: http://www.uni.edu/~maclino/hybrid/sp_book_s11.pdf)
After reading the chapter, please respond to the following questions:
Of the various aspects of Sensation & Perception presented in the chapter, which did you find the most interesting? Why? Which did you find least interesting? Why? What are three things you read about in the chapter that you think will be the most useful for you in understanding Sensation & Perception? Why? What are some topics in earlier chapters that relate or fit in with this chapter? How so?
Please make sure you use the terms, terminology and concepts you have learned so far in the class. It should be apparent from reading your post that you are a college student well underway in a course in psychology.
Make a list of key terms and concepts you used in your post.
Let me know if you have any questions.
--Dr. M
One topic that I found interesting from this chapter was Basic qualities of sound waves. I found this interesting because sound waves are simply fluctuations in air pressure across time. These sounds waves have varying amplitude, or the difference between the highest pressure area and the lowest pressure area. These differences in pressure can be very close together or far apart. By noting how quickly the pressure fluctuates we can get the frequency of the sound wave. Frequency is often measured in hertz, where one hertz equals one cycle per second. When looking at sound we often think of the psychological aspects such as loudness and pitch. Loudness is the psychological aspect of sound related to perceived intensity or magnitude. Pitch is the psychological aspect of sound related mainly to the fundamental frequency. Low frequencies correspond with low sounds and high frequencies correspond with high sounds. How can we describe differences in amplitude across a broad range of sound levels? We use units called decibels, or a unit of measure for the physical intensity of sound. Another topic that I found interesting was sine waves, or pure tones. The air pressure in a sine wave changes continuously at the same frequency. The amount of time it takes to complete one cycle of a sine wave is the period of the wave. Sine waves are not very common, because few vibrations in the world are that pure. Some examples of sine waves would be the tone of a hearing test or a tuning fork. Other than these sounds most everything else is a complex tone, or a sound wave consisting of more than one sinusoidal component of different frequencies. These complex sounds consist of a number of sine waves, these sounds can be divided into a set of sine waves by a mathematical theorem called Fourier analysis. This theorem can be represented visually with a graph called a spectrum that shows the intensity of each sine wave frequency found in the complex tone. One topic that I did not find very interesting was the section on hearing lost. I felt that this section could have included some more information. Another topic I found difficult was basic operating characteristics of the auditory system. I found this to be a difficult topic to understand. One topic that I would like to go over in class is the basic structure of the mammalian auditory system.
Terms
Amplitude, Intensity, Frequency, Hertz, Loudness, Pitch, Decibel , Sine Wave, period, complex tone, Fourier analysis, spectrum
One aspect that I find very interesting is acoustic reflex. The acoustic reflex is a reflex that protects the ear from loud noises because of the contraction of the stapedius and tensor tympani muscles. These two muscles tense when hearing a loud sound and it restricts the movement of the ossicles - the three bones inside the ear. If the ossicles don't move then sound can't be heard. Although this reflex is a good thing for us to have, it can only protect us against noises that are somewhat sustained. It doesn't protect us against sudden sounds, like a gunshot. I think this concept is interesting because I never knew there was something that helped protect us against loud noises. It also helps me to understand why listening to a gunshot is so incredibly loud compared to other loud things like a loud engine.
Something I found least interesting is the Fourier analysis. The Fourier analysis is a theorem that any sound can be divided into a set of sine waves – “the waveform for which variation as a function of time”. This would be done with complex tones, which are sound waves that consist of multiple different frequencies. The Fourier analysis simply breaks down the complex tones into sine waves, or pure tones. I find this uninteresting because I don’t see the point in breaking down complex tones into sine waves.
Three things I read that will be useful in understanding sensation and perception are frequency, amplitude, and decibel. Frequency is the number of times per second that a pattern of pressure change repeats. The higher the frequency, the higher the pitch (and vice versa). Amplitude is the magnitude of the pressure change in a sound wave. If the amplitude is higher, something is louder, and vice versa. Decibel is a unit of measurement for the physical intensity of sound. Decibels describe differences in amplitude. I think that these three concepts are most important because they are part of many other concepts in this chapter like place code, characteristic frequency, or equal-loudness curve.
Some topics that relate to earlier chapters about vision are white noise and the low/mid/high-spontaneous fibers. White noise is a signal that includes equal amounts of each frequency. This is similar to white light in vision because white light includes all frequencies of the visible spectrum. I think that the low/mid/high-spontaneous fibers are similar to the three cones because each fiber has a different firing rate depending on the frequency it detects. They’re similar to cones because each of the three cones has different peak intensities for when it can detect a wavelength.
Terms: acoustic reflex, stapedius, tensor tympani muscles, ossicles, Fourier analysis, sine waves, complex tones, frequency, pure tones, amplitude, decibel, pitch, place code, characteristic frequency, equal-loudness curve, low/mid/high-spontaneous fibers, white noise, white light, cones, intensity
Wow..there is a lot of information in this chapter. The first thing I will discuss from this chapter are the things that I found to be the most important or useful to understanding Sensation and Perception. The first thing that I read in this chapter that helped me have a better understanding of sensation and perception is the basic structure of the mammalian auditory system. There are three main parts to the basic structure: the outer ear, middle ear, and inner ear.
The pinna, or more commonly referred to as the outer, funnel-like part of the ear, collects sound from the environment. One interesting fact is that only mammals have pinnae. Also, the shape and size of the pinnae play an important role in our ability to localize sound sources. Once sound enters the Pinna, the sound waves are then funneled into and through the ear canal (the canal that conducts sound vibrations from the pinna to the tympanic membrane and prevents damage to the tympanic membrane). The length and shape of the ear canal enhance sound frequencies between about 2000 and 6000 Hz. The main purpose of the canal is to insulate the structure at its end, the tympanic membrane (eardrum). The tympanic membrane is a thin sheet of skin at the end of the outer ear canal. The tympanic membrane vibrates in response to sound.
The middle ear consists of three tiny bones, the ossicles, that amplify sound waves. The first ossicle, the malleus, is connected to the tympanic membrane on one sides and to the second ossicle, the incus on the other. The Malleus receives vibration from the tympanic membrane and is attached to the incus. The incus is connected in turn to the stapes. The main purpose of the incus is to connect the malleus and stapes. The stapes transmits the vibrations of sound waves to the oval window. The oval window is the flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside. The ossicles, amplify sound vibrations in two different ways. The first is the joints between the bones are hinged in a way that makes them work like levers: a modest amount of energy on one side of the fulcrum(joint) becomes larger on the other. The second way the ossicles increase the energy transmitted to the inner ear is by concentration energy from a larger to a smaller surface ares: the tympanic membrane which is moved by the stapes. Therefore the prussure on the oval window is magnified 18 times relative to the pressure on the tympanic membrane.
The inner ear is a little more complicated than the outer and middle ear. The function of the inner ear is to translate the fine changes in sound pressure in the environment to neural signals that inform the listener about the world around them. The first major structure in the inner ear is the cochlea, a spiral structure of the inner ear containing the organ of Corti. The cochlea is filled with watery fluids in three parallel canals: the tympanic canal (a fluid-filled passages the extends from the round window at the base of the cochlea to the helicotrema at the apex), the vestibular canal (a fluid-filled passages that extends from the round window at the base of the cochlea to the helicotrema at the apex), and the middle canal (tympanic and vestibular canals at the apex of the cochlea). The Helicotrema is the connection between the tympanic and vestibular cnals at the apex of the cochlea. The three canals of the cochlea are separated by two membranes: reissner's membrane (a think sheath of tissue separating the vestibular and middle canals), and the basilar membrane (a plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals). The basilar membrane forms the base of the cochlear partition, a complex structure though which sound waves are transduced into neural signals. Vibrations transmitted through the tympanic membrane and middle-ear bones cause the stapes to push and pull the flexible oval window in and out of the vestibular canal at the base of the cochlea. This movement of the oval window cause waves of pressure changes, called traveling waves to flow through the fluid in the vestibular canal. IF sounds are extremely intense, any pressure that remains is transmitted throught the helicotrema and back to the cochlear base through the tympanic canal where is is absorbed by another membrane called the round window. The organ of the coti is another important part of the inner ear. it translats movements of the cochlear partition into neural signals. This organ is made up of specialized neurons called hair cells, dendrites of auditory nerve fibers that terminate at the base of hair cells, and scaffold of supporting cells. Hair cells are cells that support the stereocilia that transduce mechanical movement into neural activity sent to the brain stem. They recieve input from the brain as well. Auditory nerve fibers are a collection of neurons that convey information from hair cells to and from the brain stem. Stereolcilia are hairlike extensions of tips of hair cells that initiate the release of neurotransmitters when they are flexed. The tectorial membrane (a gelatinous structure attached on one end, extending tinto the middle canal floating above inner hair cells and touching outer hair cells.
This was all very confusing to me...it was a lot of information in a short period of time. However there is one paragraph in the book the discribes the whole process which helped me understand it a litle better. "An air pressure wave is funneled by the pinna through the auditory canal to the tympanic membrane, which vibrates back and forth in time with the sound wave. the tympanic membrane moves the malleus, which moves the incus, which moves the stapes, which pushes and pulls on the oval window. the movement of the oval window causes pressure bulges to move down the length of the vestibular canal, and these bulges in the vestibular canal displace the middle canal up and down. this up and down motion forces the tectorial membrane to shear across the organ of corti, moving the stereocila atop hair cells back and forth. the flexing of the stereocilia starts a chain of biochemical reactions that results in the release of neurotransmitters into synapses between the hair cells and dendrites of auditory nerve fibers. these neurotransmitters initiate action potentials in the auditory nerve fibers that are carried back into the brain."
Another thing that I found interesting in this chapter was the discussion of sine waves, complex tones, and fourier analysis. One of the simplest kinds of sounds is a sine wave or pure tone. a sine wave is a waveform for which variation as a function of time is a sine function. the air pressure in a sine wave changes continuously at the same frequency. the time taken for one complete cycle of a sine wave is the period of the sine wave, and there are 360 degrees across one period. Sine waves are not common everday sounds. flutes can produce musical notes that are close to pure tones. most other sounds in the world are complext tones (a sound waved consisting of more than one sinusoidal component of different frequencies). All sounds, no matter how complex can be bescribed as some combination of sine waves. Fourier analysis is a mathematical theorem by which any sound can be divided into a set of sine waves. combining these sine waves will reproduce the original sound.
Another thing that I found interesting in this chapter is the discussion over psychoacoustics. Psychoacoustics is the study of the psychological correlates of the physical dimensions of acoustics: a branch of psychophysics. They play a sound and ask actual human listeners, what they hear. When human listeners are asked to report their auditory sensations, their answers are due partly to the acoustic properties of the sound signal and partly psychological characteristics of the listeners.
Something that I didn't find very interesting in this chapter is the discussion over intensity and loudness. This section just discussed the human audibility threshold, which is a graph of the lowest sound pressure level that can be reliably detected across the frequency range of human hearing. Another thing discussed in this section is a process called temporal integration. Temporal integration is the process by which a sound at a constant level is perceived as being louder when it is of greater duration. the term also applies to perceived brightness, which depends on the duration of light. This is also something that is mentioned in this chapter that relates to previous information that we have learned about sensation and perception.
One way that this chapter related to previous chapters is through the explanation of the ear and how it works. The authors spent a great deal of time discussing how the ear system is similar to the visual system. I think they thought it would help us understand the topic easier but it actually confused me more.
Terms: pinna, ear canal, tympanic membrane, ossicles, malleus, incus, stapes, oval window, Cochlea, tympanic canal, vestibular canal, the middle canal, helicotrema, reissners membrane, basilar membrane, basilar membrane, cochlear partition, round window, organ of corti, hair cells, auditory nerve fibers, Steereocilia, tectorial membrane, sine waves, complex tones, fourier analysis, period, phase, psychoacoustics, temporal integration, audibility threshold
From chapter 9 the most interesting to me was to read about hearing loss.Hearing loss caused by problems with the bones of the middle ear. (conductive hearing loss). As a result of infection, the inflammation of the middle ear called otitis media. The more serious type of conductive loss is otosclerosis which is caused by abnormal growth of the middle ear bones around the oval window. The only thing that can helps is surgery; can free the stapes from these bone growths and improve hearing. The most common hearting loss is sensorineural hearing loss, its due to defects in the cochlea or auditory nerve. Most often it occurs when hair cells are injured. Why am I interested in it? Because my family has been hearing problems so this topic is the closest to me.
The least interesting to me was the coding of amplitude and frequency in the cochlea and the auditory never; its pretty complicated.
The mot useful topics to help understanding sensation and perception would be the explanation of what sound is and how does it work as well as the basic structure of the mammalian auditory system; these topics are very related to sensation, hearing is one of our senses so its very important as much as seeing or touching, or smelling.
the hearing loss and different types of it are somehow related to previous chapters in a meaning of some disorders and diseases that the author was talking earlier in context of seeing.
Also, the brain structures, and nerve system.
conductive hearing loss
otitis media
otosclerosis
sensorinerual hearing loss
ototoxic
outer ear
middle ear
inner ear
hair cells
the auditory nerve
After spending so much time on the visual system it was a nice change of pace to learn about how we hear. The sound that we hear is a product of the vibration of objects; this produces pressure changes or waves that travel to our ears. The amplitude of the wave is the magnitude of this pressure change and is related to how loud the sound is. The speed at which the pressure fluctuates is the frequency and is associated with the pitch of the sound. Vision and hearing are similar in a way because we only perceive a portion of the physical world in both cases. We see and hear a minor fraction of available light and sound. A pure tone (sin wave) is when the pressure changes are continuous and at the same frequency. Most sounds that we actualy hear are not pure tones but are complex tones (more than one sine wave component). However, these complex tones can be broken down in sin waves by mathematical Fourier analysis. I also found the complexity of the structure of even just the ear to be very interesting. I felt as though this was another area where the visual system and auditory system overlapped for me. Prior to this class I overlooked the complexities of both the eyes and the ears roles in their respective systems. Sounds are captured by the curly funnel part of the ear called the pinna. Sound then goes through the ear canal and into the head. The canal enhances sound frequencies and acts as an insulator for the tympanic membrane (ear drum) protecting it from damage. The ear drum moves in response to the pressure changes as a result from sound waves. The pinna and ear canal (outer ear) is the area where the sound is captured and from here it is taken to the middle ear. The middle ear has ossicles (little bones) that enhance sound. The three small bones are the malleus, incus, and stapes. The malleus is connected to the ear drum and the incus, the incus is then connected to the stapes. The stapes then lets the vibrations into the oval window (opening of the cochlea). The oval window is the membrane between the middle and inner ear. The ossicles act to increase the sound vibrations and is helpful in how we hear faint sounds. This was also interesting because the author explained that if we didn’t have the ossicles much of the faint sounds would not be heard because of the fluid within the inner ear has to have a higher energy to get through than it would if it were air. The inner ear is a very important part of the auditory system because it is where these pressure changes are transduced into neural energy so that we can interpret them. Within our temporal bone we have a cochlea,which is filled with fluid and has three canals. The tympanic and vestibular canals are connected to each other b the heilicotrema (small opening). The three canals are separated by the Reissener’s membrane (between vestibular and middle) and basilar membrane (between middle and tympanic). The basal membrane forms part of the cochlear partition which is where the waves are transduced into neural signals. Vibrations go through the tympanic membrane and middle ear which causes the stapes to move the oval window. Movement of the oval window causes pressure changes to flow through the vesibular canal. From here the sound waves travel down to the apex . I found it interesting that the round window at the base of the tympanic canal releases excess pressure to deal with intense sounds. The organ of Corti is along the top of the basilar membrane and is where the movements of the cochlear partition are changed into neural signals. It contains hair cells which transduce mechanical movement in the cochlea ad vestibular labyrinth into neural energy for the brain and auditory nerve fibers which are neurons that send afferent information to brain from cochlea and also efferent information from the brain stem. The hair cells work because they have stereocillia which are on the tips of hair cells and release neurotransmitters when hair cells are flexed. As I mentioned earlier I found the complexity of the auditory systems structures and functions interesting but I also found this process to be somewhat convoluted and I would benefit from more time spent on this in class. I also would like spend time on the coding of amplitude and frequency in the cochlea better because I found this a little confusing. I understand that the larger the amplitude the faster the neural firing rate but not how different parts of the cochlear partition are displaced to different degrees by different sound waves. The different parts of the cochlea are tuned to different frequencies (place code) but I don’t really understand how. Overall I found this chapter quite challenging and I hope to delve deeper into the complexities of hearing, I previously assumed it was a much simpler process.
Terms: Amplitude, frequency, pitch, pure tone, tympanic membrane, Fourier analysis, pinna, ossicles, malleus, stapes, basilar membrane, cochlear partition, oval window, organ of corti,stereocillia
One thing I read in Ch. 9 Hearing that I think will be useful in understanding Sensation & Perception is the discussion of what SOUND is. Sounds are created by vibrations that through a pattern of displacement create sound waves that travel at particular speeds. SOUND WAVES have two basic qualities: frequency and amplitude. AMPLITUDE is the magnitude of displacement (increase or decrease) of a sound pressure wave or of a head movement. DECIBEL (dB) is a unit of measure for the physical intensity of sound in other words decibel describes differences in amplitude. Amplitude is associated with loudness quality. LOUDNESS is the psychological aspect of sound related to perceived intensity or magnitude. FREQUENCY is the number of times per second that a pattern of pressure change repeats and this is most often how we describe sound wave patterns. Frequency is measured in HERTZ (Hz) where one hertz equals one cycle per second. Frequency is related to pitch. PITCH is the psychological aspect of sound related to frequency; low-frequency sounds are low in pitch and high-frequency sounds are high in pitch. There are different kinds of sounds. A SINE WAVE (pure tone) is the simplest and the air pressure is changing continuously (SINUSOIDALLY) at the same frequency. However, most sounds we hear are complex. COMPLEX TONES are sound waves consisting of more than one sinusoidal component of different frequencies. Using the FOURIER ANALYSIS, a mathematical theorem, any sound can be divided into a set of sine waves and combining those will reproduce the original sound. TIMBRE on the other hand is a psychological sensation where a listener can determine differentiations in loudness and pitch between two sounds
A second thing I found useful in understanding S&P was the discussion of the basic structure of the mammalian auditory system. Our auditory system consists of three basic structures and a complex system of neurological functioning. The OUTER EAR is the part of the ear that is visible to and is the external sound-gathering portion of the ear consisting of the pinna and the ear canal. PINNA is the outer, funnel-like part of the ear which funnels sound waves to the ear canal. The EAR CANAL conducts sound vibrations to the tympanic membrane and also prevents damage to it as well. The TYMPANIC MEMBRANE is the eardrum which is a thin sheet of skin at the end of the outer ear canal which vibrates in response to sound. This is also the border between the outer and middle ear. The MIDDLE EAR is an air-filled chamber containing the middle bones and conveys & amplifies vibration from the tympanic membrane to the oval window. The middle ear consists of bones called OSSICLES and they are the smallest bones in the body. The three ossicles are: MALLEUS (receives vibration from tympanic membrane), INCUS (connects malleus to stapes), and STAPES (presses against oval window). The OVAL WINDOW is the flexible opening to the cochlea through which the stapes transmits vibrations to the fluid inside. The ossicles provide amplification through the use of hinged joints that act as levers to increase amount of pressure change and by increasing energy transmitted to the inner ear by concentrating the energy to a smaller surface area. This allows us to hear faint sounds. For loud sounds the ossicles use muscles: TENSOR TYMPANI and STAPEDIUS. These muscles work together through the ACOUSTIC REFLEX which protects the ear from intense sounds by contracting the muscles. This then leads to the INNER EAR which is a hollow cavity in the temporal bone of the skull and consists of the cochlea and vestibular canals. This is where sound pressure changes are translated into neural signals. The COCHLEA is a spiral structure that contains the organ of Corti. It is also filled with three water filled canals: TYMPANIC, VESTIBULAR, and MIDDLE. The ROUND WINDOW is a soft area of tissue at the base of the tympanic canal that releases excess pressure remaining from extremely intense sounds. The ORGAN OF CORTI is a structure on the BASILAR (base) MEMBRANE of the cochlea and is composed of hair cells and dendrites of auditory nerve fibers. HAIR CELLS transducer mechanical movement into neural activity that is sent to the brain stem via use of AUDITORY NERVE FIBERS (collection of neurons that convey info from hair cells to the brain stem). STEREOCILIA initiate the release of neurotransmitters when they are flexed via use of a TIP LINK a tiny filament that stretches from the tip of the stereoscilium to the side of its neighbor. From here the firing of auditory nerve fibers completes the process of translating sound waves into patterns of neural activity.
The third topic I found most useful was the discussion of the basic operation characteristics of the auditory system. PSYCHOACOUSTICS is the study of the psychological correlates of the physical dimensions of acoustics. This area of study is interested in peoples perceptions of intensity & loudness and frequency & pitch. One way to study intensity & loudness is through the audibility threshold. The AUDIBILITY THRESHOLD is the lowest sound pressure level that can be reliably detected at a given frequency. Higher and lower frequency sound waves must have larger amplitudes in order to be heard. One pheonomenon that occurs in relation to this is that longer sounds are heard as being louder due to TEMPORAL INTEGRATION this also applies to perceived brightness. For frequency & pitch it has been found that for any given frequency increase, listeners will perceive a greater rise in pitch for lower frequencies than higher frequencies.
The topic I found the least interesting was the discussion of the auditory nerve. This section discusses the THRESHOLD TUNING CURVE which is a map plotting the thresholds of a neuron or fiber in respons to sive waves with varying frequences at the lowest intensity that will give rise to a response. This discussion was extremely complex and I think it would be helpful to go over in class.
The topic I found most interesting was the section on hearing loss. My sister actually has hearing loss due to radiation and chemotherapy treatment she received as a toddler for cancer. I found it interesting that damage to any of the auditory structures can result in some form of hearing loss. The simplest way is to obstruct the ear canal which inhibits the ability of sound waves to exert pressure on the tympanic membrane. CONDUCTIVE HEARING LOSS is caused by problems with the bones of the middle ear which impairs their ability to convey vibrations from the tympanic membrane to the oval window. This often occurs when a person suffers from OTITIS MEDIA an inflammation of the middle ear resulting in an ear infection. Normal hearing usually returns after mucus is absorbed. OTOSCLEROSIS is the abnormal growth of the middle ear bones that causes hearing loss. Surgery can sometimes help this by freeing the stapes from bone growths to improve hearing. SENSORINEURAL HEARING LOSS is hearing loss due to defects in the cochlea or auditory nerve. This most often occurs when hair cells are injured. OTOTOXIC drugs can produce adverse effects on organs or nerves involving hearing or balance. Certain antibiotics and cancer drugs are ototocix and kill hair cells directly. Hair cells can also be damaged through excessive exposure to noise and excessive sound levels. Hearing loss is also a natural result of aging and most often first affects high frequency perception. Modern hearing aids are used to amplify the signal while compressing intensity differences to keep it a comfortable level. However, it does not help to direct which sound they want to hear. Background noise is amplified just as much.
My sister often has trouble hearing us talk while driving in the car and in areas with a lot of background noise. However, since a young age she has learned to lip read in order to compensate for the times she cannot hear a person’s voice above the background noise. Even with her very expensive hearing aids that were made specifically for her type of hearing loss it is still difficult. She only wears her hearing aids to work because they often cause her to get headaches. Just think if you were used to only hearing about half the amount of sounds in your environment to hearing almost 80-95 percent of the sounds, how much of a headache that would be!
TERMS: sound, sound waves, amplitude, decibel, loudness, frequency, hertz, pitch, sine wave, sinusoidal, complex tones, fourier analysis, timbre, outer ear, pinna, ear canal, tympanic membrane, middle ear, ossicles, malleus, incus, stapes, oval window, tensor tympani, stapedius, acoustic reflex, inner ear, cochlea, tympanic canal, vestibular canal, middle canal, round window, organ or Corti, basilar membrane, hair cells, auditory nerve fibers, stereocilia, tip link, psychoacoustics, audibility threshold, temporal integration, threshold tuning curves, conductive hearing loss, otitis media, otosclerosis, sensorineural hearing loss, ototoxic
What I found most interesting was the basic concept of the ear, which includes: outer, middle, inner and so forth. According to the outer ear, sounds are first collected from the environment by the Pinna, the curly structure on the side of the head that we typically call an ear. Sound waves are funneled by the pinna into and through the ear canal, which extends about 25mm into the head. The ear canal conducts sound vibrations from the pinna to the tympanic membrane and prevents damage to the tympanic membrane. The main purpose of the canal is to insulate the structure at its end, the tympanic membrane (eardrum), from damage. The tympanic membrane is a thin sheet of skin that moves in and out in response to the pressure changes of sound waves. According to the middle ear, the pinna and the ear cancal together make up a division of the auditory system called the outer ear. The typpanic membrane is the border between the outer ear and the middle ear, which consists of three tiny bones, the ossicles that amplify sound waves. The first ossicle, the malleus, is connected to the tympanic membrane on one side and to the second ossicle, the incus, on the other. The incus is connected in turn to the stapes, which transmits the vibrations of sound waves to the oval window, another membrane; which forms the border between the middle and inner ear. The inner ear is a hollow cavity in the temporal bone of the skill and the structes within this cavity: the cochlea and vestibular canals. The ossicles, which are the smallest bone in the human body, amplify sound vibrations in two ways. First, the joints between the bones are hinged in away that makes them work like livers: a modest amount of energy on one side of the fulcrum becomes larger on the other. The second way the ossicles increase the energy transmitted to the inner ear is by concentrating energy from a larger to a smaller surgace area: the tympanic membrane, which moves the malleus, is about eighteen times as large as the oval window, which is moved by the stapes. Amplification provided by the ossicles is essential to our ability to hear faint sounds because the inner ear is made up of a collection of fluid filled chambers. The ossicles play an important role for loud sounds too. The middle ear has two muscles: the tensor tympani (attached to the malleus) and the stapedius (attached to stapes). The tensor tympani and the stapedius are the smallest muscles in the body. Their main purpose is to tense when sounds are loud, restricting the movement of the ossicles and thus muffling pressure changes that might be large enough t damage the delicate structures in the inner ear. Unfortunately, this acoustic reflex follows the onset of loud sounds by about one-fifth of a second. Furthermore, the function of the inner ear with respect to sound waves in hearing is thus roughly analogous to that of the retina with respect to light waves in vision: it translates the information carried by the waves into neural signals. The major structure of the inner ear is the cochlea, a tiny coiled structure embedded in the temporal bone of the skill. The cochlea is filled with watery fluids in three parallel canals: the tympanic canal, the vestibular and middle canal. The tympanic and vestibular canals are connected by a small opening, the helicotrema, and these two canals are effectively wrapped around the middle canal. The three canals of the cochlea are separated by two membranes: Reissner’s membrane, between the vestibular canal and the middle canal and the basilar membrane, between the middle and tympanic canal. The basilar membrane forms the base of the cochlear partition, a complex structure through which sound waves are transduced into neural signals. Vibrations transmitted through the tympanic membrane and the middle ear bones cause the stapes to push and pull the flexible oval window in and out of the vestibular canal at the base of the cochlea. If sounds are extremely intense, any pressure that remains is transmitted through the helicotrema and back to the cochlear base through the tympanic canal, where it is absorbed by yet another membrane called round window.
What I found least interesting was that of the auditory nerve. The auditory nerve fibers convey information through both the rate and the timing patterns with which they fire. There are different levels of intensities. At very low intensity levels, an AN fiber will increase firing to only a very restricted range of frequencies. Threshold tuning curves is like a map that plots the thresholds of a neuron or fiber in response to sine waves with varying frequencies at the lowest intensity that will give rise to a response. The frequency to which a particular auditory nerve fiber is most sensitive is called characteristic frequency. Furthermore, a low intensity sine wave tone with a certain frequency will cause certain AN fibers to increase their firing rates, while other AN fibers continue to fire at their spontaneous rates. As long as the brain knows with AN fibers have which characteristic frequencies, the brain can interpret the pattern of firing rates across all the AN fibers to determine the frequency of any tone. The rate at which an AN fiber responds changes when energy is introduced at nearby frequencies. The phenomenon known as two-tone suppression decreases the firing rate of one auditory nerve fiber due to one tone, when a second tone is presented at the same time. When it comes to rate saturation, which is the point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable of increasing the firing rate. On the other hand rate-intensity function is a map plotting the firing rate of an AN fiber in response to a sound of constant frequency at increasing intensities. There are six fibers, all of which listen to the same hair cell.
The things I found most useful to understanding sensation and perception are including information on how hearing relates to the visual system, which has a great deal to understanding how we sense and perceive everything around us. Other things that relate are frequencies, such as the loudness frequency compared to wave frequency whether it be color or not and it relates back to the retina in some areas, such as the inner ear.
Key Terms: Pinna, ear canal, tympanic membrane, outer ear, middle ear, ossicles, malleus, incus, stapes, oval window, inner ear, tensor tympani, stapedius, acoustic reflex, cochlea, tympanic canal, vestibular canal, middle canal, helicotrema, reissner’s membrane, basilar membrane, cochlear partition, round window, two-tone suppression, rate saturation, rate-intensity function, characteristic frequency, threshold tuning curve.
Similar to visual cues, there are cues to locating where sound is. The book first talks about ITD. We can tell whether a sound is coming from our right or left because there is a difference in the time it takes to reach both ears. From the sound source extends an azimuth, or angle. The sound is depending on the location of the sound relative to the head and ear. The medial superior olives are the first places where inputs from both ears are combined within the auditory system, and the place where ITDs are located.
The second cue the book mentions is the ILD. This cue based on the loudness or intensity of the sound arriving in one ear verse the other. The head can block some of sound energy and sound pressure wave from reaching the other ear. We can tell the difference in distance according to the inverse-square law. This law states that when objects are closer to the listener, there is a large different in relative intensity. The lateral superior olive is where the combination of the differences between the ears happens. There are problems however with using the ITD and the ILD; however the issues are not major because of the many cues other than time and intensity.
Pinna filters sounds and noises different ways. The changes in elevation and in the azimuth cause the pinna to filter and interpret sound waves differently. The sum of intensity shift within complex sounds can be “measure and combined” as the Pinna. The HRTF takes into account how the position of the pinna, ear canal, head, and torso can change how we heard things. This, interesting, is why they put different sounds of the song within different earphones. It sounds more natural that way. I found that very interesting. The book states that our HRTF changes and develops with time.
Another cue can be that noise and sound gets distorted the more distance there is between you and the noise. A delay in the sound to our eyes is likely to increase as the distance increases; this is call spectral composition.
Another thing I found interesting, this chapters’ look at auditory scenes. Our natural environment, the medium for our voices can be very different. The union compared to the library. Our eyes can exclude stimuli and force on certain things. Similar our ears can separate sounds; this is called source segregation. I found spatial separation to be very interesting. That we are more like to heard moving noises, and ignore noises that are constant(very true- and like our visual. We are more likely to notice things moving than standing still). Furthermore, we are more likely to notice sounds that stand out. Different timber and onset of sounds.
ITD, azimuth,ILD, inverse-square law, relative intensity, lateral superior olive, Pinna, HRTF, Timbre,spatial separation
Finally, we're done learning about the eyes. Unfortunately, I didn't find this information extremely interesting either.
One thing I did find relatively interesting is psychoacoustics. Researchers who study psychoacoustics use human listeners for studies and have them report their auditory sensations. The auditory sensations are due to both the acoustic properties of the sound signal and to psychological characteristics. When using machines sounds are measured by frequency but humans hear pitch. The intensity of sound is measured in decibels but people hear loudness. Researchers who study psychoacoustics look at the differences between information provided from mechanical listening devices and the participants.
I found the information on the structure of the mammalian ear uninteresting. When sound waves enter the ear they first enter through the outer ear. The outer ear starts with the pinna which is unique to mammals. The pinna funnels sound waves through the ear canal (extends about 25 mm into head). The ear canal's main function is to protect the tympanic membrane (ear drum). Although it also enhances sound frequencies between about 2000 and 6000 hz. The ear drum is a thin piece of skin that moves in response to pressure changes in sound waves. The ear drum is the border between the outer and middle ear. The middle ear is made up of 3 small bones called the ossicles. The ossicles amplify sound waves. The 3 ossicles are known as the malleus, which is connected to the ear drum and the second ossicle known as the incus. The incus is then connected to the stapes which transfers the vibrations of sound waves to the oval window which is another membrane that s the opening to inner ear. The ossicles work to transmit sound vibrations in 2 different way. One, the joints between them are connected in a way that they work like levers and two they concentrate energy from a larger to a smaller surface. The middle ear also has two muscles known as the tensor tympani, which is attached to the mallus, and the stapedius, which is attached to the stapes. The purpose of these muscles is known as acoustic reflex, which is a reflex that protects the ear from intense sounds. As I mentioned the oval window is the opening to the next part of the ear known as the inner ear. The main portion of the inner ear is the cochlea which is embedded in the temporal bone of the skull. The cochlea has 3 parallel canals which are filled with watery fluids. The canals are known as the tympanic canal, the vestibular canal, and the middle canal. The helicotrema is a small opening that connects the tympanic canal and the vestibular canal. The canals have 2 membranes that separate them. The Reissner's membrane is located between the vestibular and middle canals and the basilar membrane are between the middle and tympanic canals. The basilar membrane is the base of the cochlear partition which is where sound waves are converted into neural signals. After sound waves are transmitted through the ear any excess pressure remaining from intense sounds is absorbed by a membrane called the round window. On top of the basilar membrane is the organ of Corti which converts the movements of the cochlear partition into neural signals. The organ of Corti is made of hair cells (which are specialized neurons), dendrites of auditory nerve fibers and supporting cells. The human ear has about 3500 inner hair cells arranged in one row and about 10,500 outer hair cells that are arranged in 3 rows. The inner and outer hair cells are the foundation for stereocilia which initiate the release of neurotransmitters. On top of the organ of Corti is the tectorial membrane which is attached on one end and then floats above inner hair cells to touch the outer hair cells.
Most of the information in this chapter was useful for this class so I'll go over quite a bit of it since I feel most of it is going to be important to know in the future. When an object vibrates it causes the surrounding medium (earths atmosphere) to vibrate which causes pressure changes in the medium. The pressure changes are described as waves. The magnitude of the pressure change in the sound wave is known as the amplitude (intensity) or the wave. Sound waves are generally described by how quickly the pressure fluctuates which is called the frequency of the sound wave. The amplitude of a sound wave is related to the perceptual experience of loudness whereas the frequency is related to pitch. Humans only hear a limited range of the sound waves present in their surroundings. Other animals, such as elephants or dogs have the ability to hear at much higher or lower frequencies than humans.
There are two kinds of sounds sine waves and complex tones. Sine waves, also known as pure tones, have waves that change continuously at the same frequency. These are not very common but can be heard by taking a hearing test or using a tuning fork. Otherwise the sounds you hear are complex tones. Complex tones are simply a combination of pure tones. By using a process called the Fourier Analysis complex tones can be broken down into sine waves. To show the results of the Fourier Analysis a spectrum is used which shows the intensity of each sine wave frequency found in the complex tone.
(If possible it would be helpful to go over the information on the auditory nerve in class)
The auditory nerve, or cranial nerve VIII, transfers signals from the cochlea to the cochlear nucleus in the brain stem, which is made up of several types of specialized neurons. Some of these neurons work to transfer information from the cochlea to the superior olive which is where inputs from both ears converge. Neurons from both the cochlear nucleus and the superior olive travel to the inferior collicullus. "Most of the input to each inferior colliculus comes from the opposite ear". After the inferior colliculus the information is transmitted to the medial geniculate nucleus which is located in the thalamus. This is the last step of the auditory pathway before reaching the cerebral cortex.
There was quite a bit of discussion in the chapter relating the auditory system to the visual system. I did notice a lot of similarities which I believe helped in my understanding of this chapter. One of the early similarities mentioned is the small range of light and sound waves we perceive compared to what is available in our environment. Other animals have different abilities in both lights and sounds that do humans. Another comparison made in the chapter is between the photoreceptors in the retina and the hair cells in the organ of Corti, which are both specialized neurons that convert one form of energy (sound pressure, light waves) into another (neural firing). The stereocilia on hair cells are much more sensitive that photoreceptors yet there are not nearly as many (100 million photoreceptors, 14,000 hair cells). One other comparison made between the visual and auditory systems is the difference of where inputs meet up. In the visual system, the visual field remains separate far into the visual cortex but in the auditory system some of the inputs go to both sides of the brain after a single synapse.
Terms: psychoacoustics, auditory sensations, frequency, pitch, intensity, loudness, sound waves, outer ear, pinna, ear canal, tympanic membrane (ear drum), middle ear, ossicles, malleus, incus, stapes, oval window, inner ear, tensor tympani, stapedius, acoustic reflex, cochlea, temporal bone, tympanic canal, vestibular canal, middle canal, helicotrema, Teissner's membrane, Basilar membrane, cochlear partition, neural signals, round window, organ of Corti, hair cells, dendrives, auditory nerve fibers, supporting cells, inner hair cells, outer hair cells, stereocilia, neurotransmitters, tectorial membrane, medium, sound waves, amplitude (intensity), frequency, sine waves (pure tones), complex tones, Fourier Analysis, auditory nerve (cranial nerve VIII), cochlear nucleus, brain stem, neurons, superior olive, inferior colliculus, medial geniculate nucleus, thalamus, auditory pathway, cerebral cortex, visual system, light waves, photoreceptors, retina, visual field, visual cortex, synapse
Chapter 9 really opened my eyes to how easy it is to take our hearing for granted. Just like seeing, the process of hearing is much more complex than we usually think. The first question we must address is what is sound? A sound is created when objects vibrate. Simple enough. The reason for this is because of pressure change in the medium. Sound is usually talked about in terms of waves. The book talks The two basic qualities of sound waves are frequency and amplitude. First, frequency is the number of times per second that a patter of pressure change repeats. Frequency is measured in hertz (Hz). Second, amplitude is the magnitude of displacement of a sound pressure wave. This can increase of decrease. The book goes on to talk about loudness. Loudness is basically described as the more intense a sound wave, the louder a sound will be. Pitch is also related to sound waves. Pitch is closely related to frequency. These are all words that we have heard before but never took time to figure out what they really mean. Another word I have heard before is dcible (dB). I remember growing up my mom was a very loud talker, and my dad would always tell her “lower your voice one decibel”. This was one of those words that I never truly knew what it meant. The book describes a decibel as a unit of measure for the physical intensity of sound. This may seem obvious but I think it is necessary to point out; the sounds that we hear throughout the day vary greatly in intensity.
The next section of this chapter talks about sine waves, complex tones, and fourier analysis (all words that I have never heard of before). I feel like this part of the chapter is where things began to get complicated. First, a sine wave also called pure tone is one of the simplest kinds of sound. Next, a period is the time taken to complete one sound wave. Phase must also be talked about when talking about sound, this is the relative position in time. I found complex tones to be very interesting. Complex tones are sound waves that consist of more than one different frequency. When I heard the work fourier analysis I thought to myself what the heck is that? Fourier analysis is a mathematical theorm by which sound can be divided into sound waves. The results of a Fourier can be analyzed with a graph called a spectrum.
The book throws another curve ball at me by going on to talk about the basic structure of the mammalian auditory system. This again is something I have never heard of. The outer ear is talked about first. Two parts of the outer ear are the pinna and ear canal. The pina is the outer, funnel part of the ear. The ear canal conducts sound vibrations from the pinna. The big fancy word for eardrum is the tympanic membrane. The ear canal protects the eardrum from getting damaged. The eardrum works by vibrating in response to sound. Next, the book goes into the middle ear. The middle ear consists of middle bones also called ossicles. The purpose of the middle ear is to amplify vibrations from the ear drum to the oval window. The middle ear is broken down by ossicles, these are three tiny bones in the middle ear. The first ossicle is malleous, this receives vibration from the eardrum. The next bone is the incus, it is the connection between malleus and stapes (the two other bones). The last bone is the stapes, it is connected to the malleus and also connects to the window on the cochlea. A very important part of the middle ear is the oval window. The oval window is an opening to the cochlea through which the stapes transmits vibration to the fluid inside. Next, is the inner ear. Two muscles in the inner ear are the tensor tympani and stapedius. I found the acoustic reflex to be pretty cool. The acoustic reflex protects the ear from intense sounds. The inner ear is where things really get interesting. In the inner ear are three major canals. The three major canals are the tympanic canal, the vestibular canal, and the middle canal. The tympanic and vestibular canals are connected by the helicotrema. The vestibular and middle canals are separated by a thin sheet called the Reissner’s membrane. I also found the round window to be pretty cool. The round window is a soft area of tissue at the base of the tympanic canal that releases excess pressure from intense sounds. I think it is cool that our ear has control over stuff like that.
The next section of this chapter is the organ of corti. The organ of Corti is a structure on the basilar membrane composed of hair cells and dendrites of auditory nerve fibers. Great, now with this comes more definitions. First, hair cells send and receive things from the brain. Auditory nerve fibers The neurons that send stuff from hair cells to the brain stem are auditory nerve fibers. The book goes on to talk about inner and out hair cells. There are two fibers, the first is afferent fibers, this is a neuron that carries sensory information to the central nervous system. The second is efferent fiber, this is a neurons that carries information from the central nervous system to the periphery.
The next topic in this chapter is the auditory nerve. The frequency to which a particular auditory nerve is most sensitive is the characteristic frequency.
Phase locking is a phenomena.
To be completely honest, this chapter was a chapter filled with so many tedious definitions. This chapter covered so much it was hard to keep my eyes on the big picture.
This chapter was about sound and our auditory system. Sound is created from vibrations which causes changes in pressure changes which cause waves. The difference between high and low pressure areas is amplitude (the magnitude of displacemnet of a sound pressure wave or of a head movement) or intensity of a wave(the amount of sound energy falling on a unit area (cmsq). How quickly that pressure changes is know to be frequency(the number of times per second that a pattern of pressure change repeats.) Frequency is measured in Hertz which is a unit of measure(one hertz = one cycle per second).
Three things I found to be interesting about this chapter included the outer ear, middle ear and inner ear. Sounds first go into our auditory system through the pinna which is what we refer to as the ear. I found it interesting that only mammals have this feature. The different shapes and sized of the pinna across species making your hearing better or worse. Rabbits would need better hearing than say humans because they use hearing as a survival mechanism. Sound waves are funneled through the pinna into the ear canal(conducts sound vibrations from the pinna to the tympanic membrane and prevents damage to the tympanic membrane). This canal is used as an insulator for the tympanic membrane aka ear drum. This is a thin sheet of skin at the end of the outer ear canal. The ear drum vibrates in response to sound. The ear drum is also a bridge from the outer to the middle ear. The middle ear is made up of three small bones which include the malleus(receives vibration from the tympanic membrane), stapes(connected to the incus one one end and presses against the oval window of the cochlea on the other end), and the incus(middle bone that connects the malleus and the stapes). Together the middle ear conveys and amplifies vibration from the ear drum to the oval window(the flexible opening to the cochlea through which the stapes transmits vibration tot he fluid inside. The inner ear is made up of mainly the cochlea. The cochlea is to the ear what the retina is to the eye. The cochlea is made up of three fluid canals: tympanic canal, vestibular canal, and the middle canal. I found the structure of the year to be interesting because you never think about how much goes into you hearing a song your ipod or listening to loud or soft noises.
Things that I did not find as intereting were isointensity curves(a map plotting teh firing rate of an auditory nerve fiber against varying frequencies at varying intensities), rate saturation(the point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable fo increasing the firing rate) and rate-intensity function(a map plotting the firing rate of an auditory nerve fiber in response to a sound of constant frequncy at increasing intensities). I found all of this to be less interesting because I thought the book just rambled on numbers and it lost my interest after the previous pages.
I think that this chapter will be useful for sensation and perception because this is the introductory chapter to hearing and sound. When we understand how we interprut sound it will make learning more interesting things about sound comprehendable.
I think that this chapter relates to the first chapter on vision because the ear is almost comparable to the eyes and how the eyes recognize lines and colors the ear recognizes pitch and freqency.
The tympanic membrane is a thin sheet of skin that moves in and out in response to the pressure changes of sound waves. This tympanic membrane sounds gross but I am sure that it comes in handy at a rock concert.
Chapter 10 begins by explaining sound localization. we can tell where a sound is coming from because there is a slight difference in time between when the soundwaves hit one hear then the other. Our brain is then able to triangulate this and find the position of the source of the sound. This specific point is called the azimuth. This anatomical part that does this is called the medial superior olive or (MSO) This is a relay station in the brain stem where inputs from both ears contribute to detection of the interaural time difference. Different amplitudes of sound (intensity) is called the interaural level difference (ILD) . Sounds produced closer to the ear sound closer because the pressure from the sound wave is greater than it would be from a far away point. There is an area at which we cannot tell a difference because of its close proximity to our ear. These are called cones of confusion. Another interesting point about how sound reaches our ear drum is that we each have different ear shapes (pinna) and we each adapt to the different ways in which our position effects what we hear. Different sound pitches create illusions that we perceive incorrectly. For instance, when tones occur in rapid succession they are heard as a single warbling stream. when these two tones are very distant they are heard as two separate streams.
My first fascinating topic in chapter 9 is the basic structure of the auditory system. The auditory system seems to be even more complicated than the visual system. I will start with the outer and middle Ear where sound waves are collected by the pinna and funneled through the auditory canal to the tympanic membrane. The tympanic membrane moves back and forth in response to air pressure changes caused by sound waves. This back-and-forth motion is transferred to the middle ear bones , called the malleus, incus, and stapes. The stapes pushes and pulls on the oval window, a small membrane in the wall of the cochlea, which houses the inner ear structures. It is in the inner ear that the actual neural transduction process takes place; at the end of this process, neural signals emerge through the cochlear nerve and are carried to the brain. Next is the inner ear which is a hollow cavity in the temporal bone of the skull, and the structures within this cavity are the cochlea and vestibular canals. The cochlea is really a rolled-up tube divided into three long, thin, fluid-filled chambers called canals. The oval window pushes in and out of one end of the vestibular canal. One of three fluid-filled passages in the cochlea. The vestibular canal extends from the oval window at the base of the cochlea to the helicotrema at the apex. Also called scala vestibuli. This in-and-out motion causes a traveling pressure wave to pass through the fluid in the vestibular canal and around into the tympanic canal. As the wave moves down the vestibular canal, the bulge it produces puts pressure on the middle canal, which in turn triggers another series of events in the cochlear partition that forms the base of the middle canal. The organ of Corti at the base of the cochlear partition is displaced when traveling waves pass through the fluid within the vestibular canal and causes it to bulge out which in return makes the basilar membrane, along with the inner hair cells and outer hair cells, which sit atop the basilar membrane, to move down and then back up. Hairlike bristles called stereocilia extend from the hair cells to the tectorial membrane. Because of the way it is attached to the cochlear partition, the tectorial membrane drags these stereocilia back and forth as the basilar membrane moves up and down. The back-and-forth motion of the stereocilia on the inner hair cells starts a chemical chain reaction that results in a neural impulse being generated by the hair cell. These impulses are transmitted to the brain via auditory nerve fibers, which collect together and emerge from the cochlea in the cochlear nerve.
My second fascinating topic in chapter 9 is hearing loss. My Mom and my youngest sister are deaf in their right ear. What interests is that out of 7 children only one would have loss of hearing and it is in the same ear. The book states that around 30 million Americans suffer some form of hearing impairment. Hearing can be impaired by damage to any of the structures along the chain of auditory processing from the outer ear all the way up the auditory cortex. The simplest way to introduce some hearing loss is to obstruct the ear canal, thus inhibiting the ability of sound waves to exert pressure on the tympanic membrane. This is mentioned in the first paragraph. A type of hearing loss that happens in the middle ear is called conductive hearing loss. Conductive hearing loss occurs when the middle-ear bones lose their ability to freely convey vibrations from the tympanic membrane to the oval window. This hearing loss can be causes often when the middle ear fills with mucus during ear infections. Your ear filling with mucus actually has a name called otitis media. Otitis media is the inflammation of the middle ear. We are lucky that our ear absorbs the mucus back into the surrounding tissues most of the time. Yum! There is a more serious type of conductive hearing loss called otosclerosis. Otosclerosis is cause by abnormal growth of the middle-ear bones, most typically around the oval window next to the stapes. Surgery can free the stapes from these bone growths and improve hearing. But the most common and most serious form of hearing loss is sensorineural hearing loss. This most commonly occurs inside the cochlea and sometimes as a result of damage to the auditory nerve. Hearing loss is a nasty situation especially when it is irreversible or made worse by surgery.
The topics I found least interesting in chapter 9 were the paragraphs on the isointensity curve and the two-tone suppression. An isointensity curve is a map that plots the firing rates of an auditory nerve fiber against varying frequencies at varying intensities. And the two-tone suppression is a decrease in the firing rate of one auditory nerve fiber due to one tone, when a second tone is presented at the same time.
The three things I read about in the chapter that I thought would be the most useful for me in understanding Sensation & Perception was the structure of the auditory system, the auditory nerve and the overview of different hearing loss. The structure and how it is transferred and may be not are pretty main topics on the hearing system. You could have a serious conversation with someone about the ear system after reading chapter 9.
From my own experiences and perspective I think chapter 2 relates a lot to chapter 9. I think this because chapter 2 is about the visual system. When your vision goes other senses like hearing step up to the forefront and become stronger. I know someone who lost his sight to Glaucoma. Glaucoma is the term for a family of medical problems in which the optic nerve is damaged in some way. Since this nerve is the sole carrier of information from the eye to the brain, severe optic nerve damage can result in partial or complete blindness. The most common form of glaucoma affects millions of Americans. It is a progressive disease that can be quite effectively stopped in its earliest stages. However, without a proper eye examination, many people fail to notice that anything is wrong until their vision has reached a point where there is no remedy for it. Hearing, after eyesight is lost, becomes a large part of your everyday ability to lead a semi-normal life.
TERMS: tectorial membrane, auditory system, auditory canal, outer ear, middle ear, tympanic membrane, sound waves, malleus, incus, stapes, oval window, cochlea, neural transduction, cochlear nerve, inner ear, temporal bone, vestibular canals, helicotrema, scala vestibule, tympanic canal, organ of Corti, inner hair cells, basilar membrane, outer hair cells, auditory nerve fibers, hearing loss, auditory cortex, ear canal, Otitis media, Conductive hearing loss, Otosclerosis, sensorineural hearing loss, isointensity curve, two-tone suppression