problem 6 - the ear Flashcards
parts of the outer ear
- the pinnae
- auditory canal
- tympanic membrane (ear drum)
parts of the middle ear
the ossicles:
* malleus/hammer
* incus/anvil
* stapes
- oval window
parts of the inner ear
- cochlea
- vestibular canal
- middle canal
- tympanic canal
- auditory nerve
- eustachian tube
- organ of corti
- basilar membrane
- reissner’s membrane
- tectorial membrane
the pinnae
the structures that stick out from the sides of the head
auditory canal
a tubelike structure about 3 cm long - protects the delicate structures of the middle ear
* has ear wax for protection
tympanic membrane (ear drum)
vibrates in response to sound, boundary between outer and middle ear
the ossicles
- The malleus (aka the hammer): is set into vibration by the tympanic membrane & transmits its vibrations to the incus
- The incus (aka the anvil): transmits its vibration to the stapes
- The stapes (aka stirrup): transmits its vibrations to the inner ear by pushing on the membrane covering the oval window
all 3 amplify the sound
the cochlea
- a snail-like structure
- liquid inside the cochlea is set into vibration by the movement of the stapes against the oval window
has 3 chambers:
1. vestibular canal - Reissner’s membrane (between vestibular and middle canal)
2. middle canal - basilar membrane (between middle and tympanic canal, forms the base of the Cochlear partition)
3. tympanic canal
organ of corti
A structure on the basilar membrane of the cochlea composed of hair cells and dendrites of auditory nerve fibers
hair cells
are the receptors for hearing
* the cilia (which protrude from the tops of the cells): are where the sound acts to produce electrical signals
two types of hair cells:
1. Inner: responsible for transduction
2. Outer: responsible for increasing vibration of the BM
bekesy’s place theory of hearing
States that the frequency of a sound is indicated by the place along the cochlea at which nerve firing is highest
* low frequencies cause max activity at the apex of the BM
* high frequencies cause max activity at the base (by the stapes) of the BM
auditory masking
ability to hear 1 sound is decreased by the presence of other tones
auditory masking experiment: egan & hake
- Threshold is highest around the masking tone→intensity (dB) has to be much higher for the frequency to be detected in presence of the masking tone
- Masking stimulus is asymmetrical→higher frequencies are affected more than lower frequencies
phase locking
Firing of a single neuron at one distinct point in the cycle of a sound wave at a given frequency
* The neuron need not fire on every cycle, but each firing will occur at the same point in the cycle
temporal coding
the connection between the frequency of a sound stimulus and the timing of the auditory nerve fiber firing
conductive hearing loss
Blockage of sound from reaching the receptors
sensorineural hearing loss
damage to the hair cells or to the auditory nerve
Presbycusis: loss of sensitivity that is greatest at higher frequencies - accompanies aging & affects males more severely
Noise-induced hearing loss: occurs when loud noises cause degeneration of the hair cells
what & where streams for hearing
Ventral (what) stream: starts in the anterior part of the core & belt - identifies sounds
Dorsal (where) stream: starts in the posterior part of the core & belt & extends to the parietal cortex & the prefrontal cortex - locates sounds