Exam 3 Flashcards
hearing
- we hear the change in pressure in air that surrounds us
- helps us locate objects in space
amplitude
- how loud, measured in decibels (dB)
- the height of the wave
frequency
- the pitch
- wave cycles per second
- more cycles means higher frequency
outer ear
functions to funnel sound into middle ear
middle ear
- concentrates energy/sound from a large area to a small surface area
- sound is amplified when ear drum sends info to malleus –> incus –> stapes
- stapes sends mechanical energy to oval window
- concentration of energy from ear drum to oval window goes from a high surface area to low surface area (sounds amplification)
tensor tympani and stapedius muscles
function to dampen the vibration of ossicles in order to prevent damage to ear
inner ear
made up of cochlea
organ of corti
- has 2 sets of sensory cells:
- inner hair cells
- outer hair cells
stereocilia
protrudes from each hair cell
tip links
thin fibers that run across each hair cell’s stereocilia
auditory info sent to brain
- vibration makes stereocilia sway, causing K and Ca ion channels to open
- high concentration of K+ outside cell and low concentration inside cell
- K+ enters cell when sound waves come into ear
- K+ depolarizes hair cell, causing voltage gated Ca2+ channels to open at base of cell
- Ca2+ entry causes release of glutamate or acetylcholine to ganglion neurons
- glutamate or acetylcholine activate ganglion neurons to send sound signals to brain
hair cell depolarization
hair cells are depolarized by K+
basilar membrane
- sound vibrations cause basilar membrane to oscillate
- different parts respond to different frequencies:
- high frequency –> displaces narrow base of basilar membrane
- low frequency –> displaces wider apex
inner hair cell releases…
glutamate
outer hair cell releases…
ACh
function of inner hair cells
send auditory information to brain
function of outer hair cells
amplify sound
cortical tonotopy of auditory cortex
- higher frequency in posterior auditory cortex
- lower frequency in anterior auditory cortex
encoding frequency properties of a sound
- place coding or tonotopic representation
- temporal pattern of firing of cells:
- higher firing rates for higher frequency
encoding loudness of a sound
movement of basilar membrane
sound location detection
- binaural cues signal sound location:
- intensity differences: different in loudness at the 2 ears
- latency differences between the 2 ears in the “time of arrival” of sounds
auditory pathways of human brain
cochlear nucleus –> switches side of brain –> superior ovilary nucleus –> inferior colliculus –> medial geniculate nucleus –> auditory cortex
retina
- images a mirrored upside down on retina
- contains 3 primary layers: ganglion cell layer, bipolar cell layer, photoreceptor cell layer
- contains rods and cones