audition - jullet Flashcards
Pressure waves are generated by:
vibrating air molecules
Amplitude corresponds to:
loudness
Frequency corresponds to:
pitch
complexity corresponds to:
timbre (also called tone color)
What does timbre mean?
CHARACTERISTICS and QUALITIES of sound which allow the ear to distinguish sounds that have the same pitch and loudness. Examples: warm, full, thin, cold)CHARACTERISTICS and QUALITIES of sound which allow the ear to distinguish sounds that have the same pitch and loudness. Examples: warm, full, thin, cold)CHARACTERISTICS and QUALITIES of sound which allow the ear to distinguish sounds that have the same pitch and loudness. Examples: warm, full, thin, cold)CHARACTERISTICS and QUALITIES of sound which allow the ear to distinguish sounds that have the same pitch and loudness. Examples: warm, full, thin, cold)CHARACTERISTICS and QUALITIES of sound which allow the ear to distinguish sounds that have the same pitch and loudness. Examples: warm, full, thin, cold)CHARACTERISTICS and QUALITIES of sound which allow the ear to distinguish sounds that have the same pitch and loudness. Examples: warm, full, thin, cold)CHARACTERISTICS and QUALITIES of sound which allow the ear to distinguish sounds that have the same pitch and loudness. Examples: warm, full, thin, cold)
How do sound waves expand?
sound waves expand in a spherical shell in 3D
Humans are unable to detect these frequences:
infrasound (20kHz)
What is the human auditory frequency spectrum? What is the peak sensitivity?
Range: 20-20kHz. Peak sensitivity: 2-3kHz
What frequency of speech?
2-3kHz
How does the external ear help in auditory transduction? (2)
The auricle helps to collect sound. The external acoustic meatus boosts sounds 30-100x at 3kHz
How does the middle ear help in auditory transduction? (2)
The middle ear boosts sound pressures 200x via 1) energy transfer from a larger tympanic membrane to a smaller oval window, 2) mechanical action of the 3 ossicles, but also responds to loud sounds through the 3) attenuation reflex
What is the attenutation reflex?
tensor tympani and stapedius muscle stiffens the ossicles in response to loud sounds and this reduces the amount of sound pressure transmitted ot the cochlea.
What two small muscles of the middle ear are involved in the attenutation reflex?
tensor tympani and stapedius muscle.
What is Bells palsy?
damage to tensor tympani and stapedius muscles causes them to remain flaccid, which results in hyperacusis (extra sensitivity to moderate or even low intensity sounds)
Why is amplification of sound waves important?
when sound waves travel from air to fluid, this results in a loss of pressure. Amplification is necessary to boost that pressure so that when it gets transmitted to vibrations, not much is lost.
What is the tensor tympani innervated by?
trigeminal nerve.
What is the stapedius innervated by?
facial nerve.
What normally helps to equalize pressure of he middle ear to atmospheric pressure?
eustachian tube
What produces endolymph?
stria vascularis
What part of the cochlea contains endolymph? Perilymph?
Endolymph: scale media. Perilymph: scala vestibuli/scala tympani
How is the basilar membrane different at the apex vs the base? How does it affect the vibrations?
The APEX is wider and more flexible, which results in more vibrations during LOWER frequencies. The BASE is narrower and stiffer, which results in more vibrations during HIGHER frequencies.
What is tonotopy of the basilar membrane?
systematic representation of sound frequency along the cochlea
Where are the scala vestibuli and tympani connected?
at the far end of the cochlea - the helicotrema
How is the perilymph different from the endolymph in terms of K?
Endolymph contains HIGH K concentrations and perilymph contains LOW K concentrations, which translates to a 80mV difference between the two fluids
What does the organ of corti consist of?
hair cells, support cells, and tectorial membrane
What are hair cells?
Hair cells are the sensory receptors of the auditory system and are located within the organ of cortion a thin basilar membrane in the cochlea.
The tectorial membrane overlies the outer hair cells and inner hair cells, which are connected to axons. What type of axons are connected to each?
Afferent axons forms synapses on the base of the inner hair cells and transmit information about the sound frequency to the cochlear nuclei in the CNS (via spiral ganglion), while efferent axons from the superior olivary complex travel to the outer hair cells
What is the purpose of having efferent fibers from the superior olivary complex to the outer hair cells?
Activation of the efferent fibers to the outer hair cells serves to DAMPEN the response to LOUD sounds, such that there is less response in the afferent fibers from the inner hair cells to the cochlear nuclei in the CNS (via spiral ganglion)
What’s the difference between stereocilia and kinocilia?
Stereocilia are bundles of hair extending from the apical end of the hair cell and push up against the tectorial membrane. Kinocilia is the tallest stereocilium and the only true cilia
What are tip links?
proteins that connect the tips of stereocilia in adjacent rows in the bundles.
What causes the K+ channels on hair cells to open? What causes them to close?
Movement of the stereocilia AWAY from the kinocilium causes the K channels to CLOSE (hyperpolarization). Movement of the stereocilia TOWARD the kinocilium causes the K channels to OPEN (depolarization). Think: AC-TO
What causes the stereocilia/kinocilium to bend/deflect?
vibration of the basilar membrane
What’s the difference between the basilar membrane and the tectorial membrane?
Basilar membrane - separates the scala media and the scala tympani and is where the inner hair cells and outer hair cells are attached. Tectorial membrane - a gel-like struture situated above the organ of corti and is where the stereocilia of the hair cells attach to
Why are K channels on hair cells considered to be mechano-sensitive channels.
If the cilia bends toward the longer cilia, the tip links pull open the K channels, allowing K to flow in (depolarization). If the cilia is bends away from the longer cilia, the tip links closes the K channels (hyperpolarization)
Outer hair cells display electromotility. What does this mean? What purpose does it serve?
DEPOLARIZATION: outer hair cells shorten to increase inner hair cell displacement (allows for MORE basilar membrane movement). HYPERPOLARIZATION: outer hair cells lengthen (allows for LESS basilar membrane movement). Purpose: protection mechansim used to dampen the vibrations of the basilar membrane if the sounds are too loud.
What happens to K when the K channels in the stereocilia open?
Because the endolymph has a very high conc. of K+, when the K+ channels open, K+ ions flow INTO the cell.
What is the driving force for K entry into the hair cell during depolarization?
1) the interior of the cell is negative (-45mV) due to the low K+ concentration, and the total membrane potential is equivalent to +80 mV (due to the high K+ in the endolymph). Thus there is a total of 125 mV of driving force for K+ entry into the cell.
What are the two mechanisms the middle ear employs to dampen loud sounds?
1) attenutation reflex with the tensor tympani and stapedius muscles to reduce the amount of energy the ossicles transmit to the oval window. 2) changes in the length of the outer hair cells to dampen the vibrations to the basilar membrane.
What is prestin?
motor protein on the membrane to help change the length of the cell and it helps to minimize vibrations on the basilar membrane
How do changes in the length of outer hair cells protect the cochlea from damage?
change in the length of the outer hair cells that affects the extent of the basilar membrane movement: longer hair cells stiffen the basilar membrane -> dampens vibrations in response to loud sounds and protects the cochlea from damage.