Exam 2 Flashcards
Sound
an energy wave of molecules (or pressure wave) that creates a vibration
-vibrations sets particles in the surrounding medium (typical air) in vibrational motion, thus transporting energy through the medium
-cycles per second
Frequency vs intensity and their units
Frequency is the rate of pressure fluctuations in the sound wave
-measured in Hertz (Hz)
-how often
vs.
Intensity is the magnitude of the pressure change in a sound wave (amplitude)
-measured in decibels (dB)
-how strong
Pure tone vs. Complex sounds
Pure tones are a single waveform for which variation as a function of time is a sine function (Sine wave)
vs.
Complex sounds are a combination of pure tones; different frequencies combined at different intensities
What is Fourier analysis?
a method to divide a complex sound into its pure tone components
Basic Structures of the auditory system listed in order
Outer Ear
-Pinna
-Ear canal
Tympanic membrane
Middle Ear
-Ossicles
Oval Window
Inner Ear
-Cochlea
-Organ of Corti
Basic Structures of the auditory System and their functions: Pinna
=the outer part of the ear that sticks out; the curly structure on the side of the head that we typically call an ear
-The ridges in the ear help detect and localize sounds
Basic Structures of the auditory System and their functions: Ear Canal
=the canal that conducts sound vibrations from the pinna to the tympanic membrane
-enhances sound frequencies
-conducts sound vibrations from the pinna to the tympanic membrane and prevents damage to the tympanic membrane
Basic Structures of the auditory System and their functions: Tympanic Membrane
= a thin sheet of skin that moves in and out in response to the pressure changes of sound waves
-eardrum; the border between the outer and middle ears
Basic Structures of the auditory System and their functions: Ossicles
= 3 tiny bones in the middle of the ear (MIS)
-amplify sound waves and transmit the vibrations from the tympanic membrane to the oval window
Basic Structures of the auditory System and their functions: Oval Window
the border between the middle and inner ear
-its movement causes movement of fluid within the cochlea (inner ear)
Basic Structures of the auditory System and their functions: Cochlea
=the change in pressure causes the vestibular canal to bulge in a location related to the frequency of the sound
-Interacts with the middle ear to relieve pressure
-These bulges in the vestibular canal cause the middle canal to move up and down shearing the Organ of Corti
Function of the inner hair cells
-focus on loudness and pitch
-Each stereocilia is connected to its neighbor by tip link (=a tiny filament)
-So they bend together when deflected by the shearing force
-When a stereocilium ( inner hair cell) deflects, the tip link pulls on the taller stereocilia in a way that opens an ion pore allowing potassium (K+) to flow into the cell => rapid depolarization
-The harder you pull, the more potassium is going to come in
-This depolarization leads to a rapid influx of calcium ions and initiates the release of neurotransmitters- stimulating the dendrites of the auditory nerve
Function of the outer hair cells
-Function: makes parts of the tectorial membrane stiffer through an electromotile response; works to make inner cells more sensitive and sharply tuned
-The sharpness of afferent nerve fibers connected to inner hair cells is dependent upon the outer hair cell
-Electromotor response, actually change shape/grow when stimulated
Need more force to stay sturdy
-Adds structures while inner hair cells move
How does the cochlea encode intensity?
-If the amplitude of the sound wave is increased, the tympanic membrane and oval window move farther in & out with each pressure fluctuation
=>making the bulge in the vestibular canal bigger, causing the cochlear partition to move farther up & down, causing the tectorial membrane to shear across the organ of Corti more forcefully, which causes the hair cells to pivot farther back & forth, which causes more neurotransmitters to be released, which causes auditory nerve fibers to initiate action potentials more quickly
-The location of the cochlea is frequency and how much it bends is intensity
How does the cochlea encode frequency?
-Cochlear place code= different portions of the cochlea are tuned to different frequencies
-different spots that move up and down more
-closer to oval window is high pitch/frequency, closer to the other window is low pitch/frequency
-The location of the cochlea is frequency and how much it bends is intensity