Anatomy of the Ear What are the major components of the outer middle and inner ear What membranes separate the middle ear from the outer ear and the inner ear 1 Outer Ear Pinna important in localizing sound only found in mammals Ear Canal Tympanic Membrane 2 Middle Ear separated by outer ear by tympanic membrane air filled Ossicles 3 bones malleus incus stapes conducts sound vibrations joints between bones make them work like levers concentrates energy from larger surface to smaller surface muscles tensor tympani and stapedius Oval Window separates middle ear and inner ear Inner Ear Cochlea audition Semicircular canals vestibular system Otolith Signals vestibular system 3 What is the purpose of the pinna localization of sound What is the function of the ossicles and know their names too Why is this function necessary how is it accomplished Ossicles 3 bones malleus incus stapes conducts sound vibrations joints between bones make them work like levers concentrates energy from larger surface to smaller surface What are the muscles in the middle ear and what is their function What is the acoustic reflex Muscles tensor tympani and stapedius Acoustic reflex muscles tense with loud sounds and self generated sounds such as chewing and swallowing Could you describe the anatomy of the cochlea What are the 3 long fluid filled canals What membranes separate them Where are the oval window and the round window What is the helicotrema What makes up the cochlear partition Cochlea like a rolled up straw that has 3 canals instead of 1 1 3 parallel fluid filled canals rolled up like a snail 2 Vestibular canal and tympanic canal separated lengthwise by middle canal and cochlear partition 3 Reissner s membrane separates vestibular canal and middle canal 4 Basilar membrane separates middle canal and tympanic canal 5 Organ of Corti is a structure on the Basilar membrane composed of hair cells and dendrites of auditory nerve fibers overlain by tectorial membrane 6 Cochelar partition combined basilar membrane tectorial membrane and organ of Corti responsible for transduction oval window border between middle and lower ear Helicotrema the opening that connects the tympanic and vestibular canals at the apex of the cochlea Round window a soft area of tissue at the base of the tympanic canal that releases excess pressure remaining from extremely intense sounds Any pressure left at apex travels thru helicotrema thru tympanic canal and is absorbed at the base of the cochlea by the round window What are the differences physical and functional between the inner hair cells and the outer hair cells How are the hair cells stimulated What happens w in the cells when they are stimulated ie what ion comes in first and how is its channel opened what ion comes in next how is its channel opened What is the result of stimulation of a hair cell I ll tell you a receptor potential What s that Inner hair cells 1 row 3 500 afferent to the brain arranged front to back shortest to tallest most auditory info 90 95 of auditory nerve fibers come from synapses with IHCs stereocilia of IHCs barely touch tectorial membrane Outer hair cells 3 rows 10 500 efferent from the brain arranged as a V or W tall stereocilia of OHCs embedded in tectorial membrane Hair cells are stimulated when vibration displacement of the cochlear partition makes the tectorial membrane sheer across the width of the cochlear partition which bends stereocilia back and forth Stereocilia bend toward tallest tip links stretch which pulls open potassium channels potassium flows into hair cell which depolarizes the cell and causes voltage gated calcium channels to open and calcium enters the cell which releases a neurotransmitter glutamate from the base of hair cell onto fiber of auditory nerve to start an AP Receptor potential a change in voltage across the membrane of sensory receptor cell in response to stimulation this is a type of graded potential So based on the above 2 sets of questions you should understand and be able to explain the sequence of events leading from a sound wave entering the ear all the way to the firing of auditory nerve fibers Sound and Coding in the Cochlea What are the 2 main components of sound and what are their psychological correlates Amplitude intensity measured in dB correspond to loudness Frequency Hertz 1 Hz 1 cycle sec humans hear from about 20 20 000 Hz corresponds to pitch Why do we use a log scale for decibels log scales compress a large range into a smaller range What is an audiogram What is a spectrogram What is a sonogram Audiogram graph of the thresholds of hearing over different frequencies Spectrogram representation of the relative energy intensity present at each frequency Sonogram plot a spectrum over time x axis represents time y axis represents frequency darkness of lines represents amplitude What is the difference between a pure tone and a complex tone Pure tone 1 frequency at 1 amplitude sine wave Complex tone real sounds multiple frequencies at various amplitudes What are Fourier Analysis and Fourier Synthesis Fourier Analysis complex sounds can be broken down into their pure tone components Fourier Synthesis A complex sound can be created by adding pure tone components What is the fundamental frequency What are harmonics What is timbre and what does timbre have to do with harmonics Fundamental frequency lowest tone in the harmonic series Harmonics a tone that is a component of a complex sound whole number multiple of the fundamental frequency harmonics are always evenly spaced mulitples of the fundamental frequency so the higher the fundament frequency pitch the further apart the harmonics will be Timbre perceptual quality of a complex sound altered by combinations of harmonics Why do different instruments playing the same note sound different Timbre different vibrating sources What are equal loudness curves How are amplitude and frequency coded in the cochlea Equal loudness curve for a single contour tones of different frequencies have different physical intensities but they sound equally loud you can pick a frequency then adjust the amplitude and have listener judge how loudness changes over 40 dB to double perceived loudness have to more than double acoustic energy so perception dos not increase as fast as sensation Here are some terms to know place code temporal code frequency matching phase locking volley principle 2 tone suppression rate saturation Place code different frequencies displace different regions
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