lecture 10 Flashcards
Hearing is a form of Mechanosensation
how does it work
Mechanical energy (sound waves) electrochemical energy via mechanosensors in the ear.
why is hearing important
-Orientation of the body to a novel stimulus
-Primary mode of communication
Speech
Music/Expression
audition
refers to our sense of hearing.
depends upon our ability to detect sound waves.
Sound waves are periodic compressions of air, water or other media.
Sound waves are “transduced” into action potentials sent to the brain.
physical properties of sound
frequency amplitude
perceptual
pitch loudness
human hearing sensitivity range
20hz to 20 khz
upper limit declines with age
sound frequency (pitch)
low frequency more spread apart
high frequency close together
sound amplitude
soft sound shorter
loud sound taller
outer ear structures and functions
Pinna, Concha and auditory meatus
collects sound waves and directs them to the auditory canal
pinnae
Can move to determine the source of a sound
what are the structures of the middle ear
tympanic membrane ossicles (malleus, incus, & stapes)
tympanic membrane
vibrates when struck by sound waves
what happens in the middle ear
sound is sent in to the middle ear to the tympanic membrane which vibrates when struck by sound waves.
Three tiny bones or ossicles (malleus, incus, & stapes) transmit information to the oval window of the cochlea.
the stimulus through the inner ear
Vibrations against the oval window are transmitted into the cochlea.
The cochlea contains hair cells which are the mechanoreceptors for sound
cochlea
in the inner ear is a fluid-filled organ of hearing.
conduction pathways of sound ways
Air-> Bone -> Membrane -> Fluid -> Hair Cell -> CNS
hair cells
auditory receptors that excite the auditory nerve when displaced by vibrations in the fluid of the cochlea
Found in the cochlea for auditory sound processing and the vestibular system
Detects the position and the movement of the head.
Directs compensatory movements of the eye and helps to maintain balance.
The vestibular organ is in the ear and is adjacent to the cochlea.
Where are the mechanosenesor located on the hair cells?
stereocilia
tension:
opens channels
*slack:
lets channels close
[*not “compression”]
Fluid wave moves
Membranes move
Steriocilia move
Ion channels open
Depolarization
Glutamate release
Sensory nerve
action potentialKinocilium
longest stereocilia
if bent moved away then there is tension and the channels open (ca gated channels) glutamate is released
if they are straight then there is slack
hair cell transduction
At rest: hair cells are straight 10% of channels are open and a tonic signal is sent by the sensory neuron
excitation: when the fair cells bend in one direction, the cell depolarized, which increases action potential frequency in the associated sensory neuron
inhibition: if the hair cells in the opposite direction, ion channels close, the cells hyper polarize, and the sensory neuron signaling decreases
The cochlea encodes information about the
Amplitude
Frequency
Duration of the acoustic wave
Frequency coding in the basilar membrane
base of choclea (by the oval window) has higher frequency (stiff at the base)
the apex has the lowest frequency (less stiff at the apex)
primary auditory cortex
the ultimate destination of information from the auditory system.
Located in the superior temporal cortex.
receives input from both ears
Topographic map of the cochlea
processes the sound information, can integrate it with other senses
Auditory cortex in each hemisphere receives inputs from both ears
the cochlear nucleus is on both sides of the brains hear sounds from both sound then reaches the superior olive with combines both sounds from there are the sounds are combined
