Module 3: Audition Flashcards
what are the contested sensory systems
kinesthesioception, proprioception, equilibrioception, thermoception, nociception
what is kinethesioception
sensing acceleration
what is proprioception
sensation of position
what is equilibrioception
sensation of balance
what is thermoception
sensation of temperature
what is nociception
sensation of pain
perception
the process of recognizing, interpreting, and organizing sensory information
bottom-up processing
perceptions are built from sensory input
top-down processing
interpretation of sensations is influenced by our knowledge, our experiences, and our thoughts
what do all sensory pathways require
- a stimulus
- a sensory receptor
what are sensory receptors
specialized cells or nerve endings of sensory neurons where sensory impulses originate
what is unique about sensory receptors
each one has an adequate stimulus that is unique to that receptor
what are the five main types of sensory receptors
- chemoreceptors (respond to chemical ligands)
- mechanoreceptors (respond to mechanical energy)
- thermoreceptors (temperature)
- nociceptors (painful stimuli)
- photoreceptors (light)
what is threshold
strength of stimulus sufficient to stimulate a receptor
what are the characteristics of sensory systems
- modality
- threshold
- location
- duration
what is duration in a sensory system
sufficient time for stimulus to activate
adaptation
ability of sensory receptors to adjust to stimulus presence for a long period of time
- slowly response will diminish
what is synaesthesia
union of the senses; several sensory systems work in harmony together
graphome-color synaesthesia
letters and numbers are coordinated
lexical-gustatory synaesthesia
tastes and words are coordinated
causes of synaesthesia
developmental, acquired (induced by trauma, neuropathology, or stroke), pharmacological (under effects of halucinogens)
what path do sound waves take through the auditory system
sound –> pinna –> outer canal –> tympanic membrane –> vibrations of ossicles –> vibration of membrane & oval window –> cochlea –> basilar membrane moves w/ receptors (hair cells) that are activated by sound waves –> depolarization or hyperpolarization –> auditory nerve –> cochlear nuclei –> superior olive –> inferior colliculus –> medial geniculate nucleus –> primary auditory cortex
how do sound waves affect the air
causes compressed and rarified air
what frequencies of sound do humans detect
20 Hz - 20 kHz
what frequencies is infrasound
< 20 Hz
what frequencies is ultrasound
> 20 kHz
what is sound intensity perceived as
sound loudness
formulas fr intensity
energy / (time * area)
power/area
what is the threshold of human hearing
0 dB
why do we need three little bones in the ear?
it reduces pressure on oval window since the tympanic membrane is a lot bigger
what is the auditory canal
closed tube resonator, enhances sounds in 2-5 kHz
what kind of sounds are important for humans
speech, music
what does the middle ear consist of
tympanic membrane (eardrum), ossicles: malleus (hammer), incus (anvil), stapes (stirrup)
how does the ear deal with amplification
pressure oval window is 20x > eustachian tube
what is the middle ear filled with, and how is it pressurized?
it is filled with air, and is the same pressure as outside
what are the cochlear muscles responsible for
attenuation reflex
how does the attenuation reflex work
at 70 - 90 dB the tensor tympani and stapedius muscles contract to accommodate for prolonged loud sounds
what is the cochlea filled with
fluid
what are the scala vestibuli and tympani filled with
perilymph
what is the scala media filled with
endolymph
how does endolymph relate to perilymph
endolymph electric potential 80 mV and is more positive than perilymph
what does the stria vascularis do
removes potassium to scala media and takes in sodium
- active transport
what is the shape of the cochlea
wide base –> narrow apex
what is the shape of the basilar membrane
narrow at cochlear base –> wide at apex
what is the function of the round window
allows fluid to move when the bones tap on the oval window
where do high sound frequencies travel
generate a wave that travels up the apex
where do low sound frequencies travel
waves vibrate closer to the cochlear base
what is the organ of corti
sensory area of cochlea
how many inner hair cells and outer hair cells are there
3500 inner cells (1 row) and 15000-20000 outer hair cells (3 rows)
what surrounds the somas of hair cells
perilymph
how many stereocilia do each hair cell have
100
where do afferent axons project to
inner hair cells
where do efferent axons project to
outer hair cells
what initiates auditory transduction
traveling waves
what are the two options for stereocilia’s electrical potential
either depolarized or hyperpolarized depending on which direction the hair cells move
how is receptor potential generated in hair cells
the back and forth movement between depolarization and repolarization
when are MET channels open
when the tip links (elastic filaments) joining
the stereocilia are stretched
what does the entry of Ca through the MET channels result in
release of neurotransmitter
what drives potassium through MET channels into the hair cells
electrical gradient
what does the entry of potassium do
drives depolarization
what is the function of outer hair cells
cochlear amplifier
what do spiral ganglion cells synapse with
95% synapse with inner cell and 5% synapse with outer cells
how do outer hair cells work as cochlear amplifiers
if a sound is not sufficient to move the basilar membrane, the brain tells the outer cells to move
- when outer hair cells expand they push against the tectorial membrane
what happens when outer hair cells contract
they pull the tectorial membrane in and thus move the basilar membrane
what function does the Prestin gene have
increases sensitivity to sound
how do antibiotics affect sound sensitivity
reduce sound sensitivity
what is sound intensity
firing rate of neurons
what parts of the brain might be responsible for loss of hearing in one ear
damage to anything below superior olive
where does the auditory pathway decussate
superior olive
how is the primary auditory cortex organized
tonototopically
symptoms of Broca’s aphasia
knows what they want to say but can’t get it out
- search for words, speak slowly
symptoms of Wernicke’s aphasia
speech is incoherent and makes no sense
- have reduced understanding of spoken and written language
what are the left hemisphere (specifically Wernicke’s area and Broca’s area) responsible for
speech perception and production
where is Wernicke’s area located
posterior part of the superior temporal gyrus
where is Broca’s area located
inferior frontal gyrus
what is the right hemisphere mainly responsible for
processing of tonal stimuli and music
ear advantage
infants usually prefer left ear to tones, but right for clicks
- the preference disappears with age
what is the ventral stream
“what” stream: identity of sound
what is the dorsal stream
“where” stream: location of sound
steps of the first theory of localization
- sound reaches left ear 1st
- action potential –> medial superior olive
- sound reaches right ear later
- action potential right ear –> medial superior olive
- action potentials converge on medial superior olive neurons that respond strongly
what is the function of the medial superior olive
coincidence detectors, responding most when excitatory signals from cochlear nuclei
what do lateral superior olives encode
they encode sound through interaural intensity
what are the steps of LSO neurons encoding sound
- stronger stimulation –> left ear excites left LSO
- stimulus inhibits right LSO via MNTB interneurons
- excitation from left side –> inhibition right side = net excitation –> higher centers
- inhibition from left side is greater than excitation from right side
what is the duplex theory
shape of pinna allows sound to enter the ear canal
cause of hearing loss
genetic, environmental (toxic sounds)
what does conductive hearing loss entail
sound doesn’t get through outer ear canal –> eardrum
possible causes of conductive hearing loss
fluid in middle ear, ear infection, perforation, benign tumors, earwax
how can conductive hearing loss be corrected
medically/surgically
what does sensorineural hearing loss entail
damage to cochlear nerve pathways or to the nerve pathways from the inner ear to the brain
possible causes of sensorineural hearing loss
drugs, loud noise, hereditary, aging, head trauma
can sensorineural hearing loss be corrected?
no
possible corrections for sensorineural hearing loss
hearing aid, cochlear implant (if there are no functioning hair cells with unaffected cochlea), gene therapy from stem cells
how do cochlear implants work
bypass the nonfunctional or absent HCs and directly stimulate SGNs
- takes advantage of the tonotopic arrangement of the auditory organ
how common is genetic hearing loss
50% of hearing loss cases are genetic
