Auditory and Visual Systems Flashcards
Amplitude
Intensity, measured in decibels (dB)
and perceived as loudness
Frequency
Measured in number of cycles per
second, or hertz (Hz), and perceived as pitch
What is the external ear composed of?
1) Pinna
2) Ear canal
Tympanic membrane
Ear drum, seals ear canal
What is the middle ear composed of ?
1) Tympanic membrane
2) Ossicles
3) Oval window
Ossicles
The malleus (hammer), incus (anvil), stapes (stirrup)
What are the ossicles connected to?
The tympanic membrane on one side and the oval window on the other side.
What do the tensor tympani and stapedius do ?
They control volume
Oval window
Connects ossicles to inner ear
& focuses vibrations from sound waves
into the inner ear.
How does sound travel through our ears?
1) Funneled into the ear canal by the pinna and reaches the ear drum
2) Ossicles work to concentrate and amplify the sound
3) Focuses the sound on the oval window which is the entrance to the inner ear
Inner Ear
The cochlea converts vibrational energy into neural activity
Where does sensory transduction occur?
Organ of Corti
The Organ of Corti
Part of the cochlea that converts sound into neural activity
What is the Organ of Corti composed of ?
Tectorial membrane, hair cells, basilar membrane
Basilar membrane
Basal end: Membrane is narrow and stiff
Apex: Membrane is wide and flexible
Tonotopically organized
Neurons or other cells within a neural structure are arranged spatially according to their sensitivity to different sound frequencies
Review steps
- Sounds are vibrations carried
through the air - Sounds pass through the external
ear and vibrate the tympanic
membrane at a similar frequency - Tympanic membrane activates the
lever-action of the ossicles which in
turn vibrate the oval window. - The oval window vibrates causing
pressure changes in the fluid filled
canals of the cochlea. - Pressure changes in fluid will kick-
start sensory transduction
What protrudes from each hair cell?
Stereocilia
Hair Cell depolarization process
- Deflection of stereocilia puts tension
on tip links - Potassium ion channels are
mechanically forced open - Potassium influxes (depolarization)
- Influx of calcium ions
- Glutamate release via exocytosis onto
auditory nerve cell
Auditory signals run from _____ to _______
Cochlea to Cortex
Vestibulocochlear nerve
Contains auditory fibers from the cochlea, contacts the bases of the hair cells
Transduction steps
1) Hair cells from the organ of corti making contact with vestibular cochlear nerve
2) Auditory nerve fibers terminate in the cochlear nuclei located in the medulla
3) The cochlear nuclei send information to the superior olivary nuclei in the pons (where decussation and binaural hearing take place)
4) Information passed to the inferior colliculi (Primary auditory centers)
5) Outputs go to the medial geniculate nuclei of the thalamus
6) Pathways from the MGN of the thalamus terminate in the primary auditory cortex
Why does the superior olive have a medial and lateral component ?
Intensity and latency differences
Duplex theory
Sound localization requires processing of both intensity and latency differences
Sensorineural deafness
Hair cells fail to respond to the movement of the basilar membrane, no action potentials fired.
Conduction deafness
Disorders of the outer or
middle ear prevent sounds
from reaching the cochlea