Sound & Ear Anatomy
The loudness of sound of a particular frequency is most closely related to this…
The difference in pressure between the compressed and rarefied air in the sound wave.
The membrane below the scala vestibuli.
What is Reissner's membrane?
What ion movement initiates auditory transduction?
Influx of K+ into stereocilia
The feature of a sound wave that encodes sound intensity.
What is amplitude?
The perception of sound in the absence of stimuli.
What is tinnitus?
A patient has normal cochlear hair cells but damage to the ossicles. This function would be most directly impaired.
Amplification of sound to the inner ear
It is said that sound transduction involves a cochlear amplifier because of this
Outer hair cells push the basilar membrane amplifying low intensity sounds
The strong driving force on K+ ions in hair cells is created by this protein.
Na/K+ ATP ase
1) The phenomenon produced by a group of phase-locked neurons.
2) The frequency range at which this is most effective.
What is 1) the Volley Principle; 2) intermediate (200-5000 Hz)?
The pathology involving poor language comprehension.
What is Wernicke's Aphasia?
Humans cannot hear very low frequency sound (less than 20 Hz) because sound energy at this low frequency...
Passes through the helicotrema thereby not vibrating the basilar membrane.
Of the basilar membrane,
1) the base is __ and __ and encodes __ frequencies;
2) the apex is __ and __ and encodes __ frequencies.
Hint: we're looking for size and rigidity
What is 1) narrow, stiff, higher; 2) wide, floppy, lower?
If an inner hair cell's stereocilia bend away from the kinocilium, this happens in the mechanically gated K+ channels and the auditory nerve fires more/less.
Mechanically gated K+ channels close, auditory nerve fires less.
The method of vertical localization involving interference of direct and indirect sound waves, which creates unique intensity ranges in the ear canal.
What is spectral shaping?
The decussation in the auditory pathway is between __ and __.
What is the Cochlear Nuclei and the Superior Olive?
The stapes pushes inward on the oval window. Describe the sequence of fluid movement that ultimately allows pressure to be relieved at the opposite end of the cochlea.
What is scala vestibuli → helicotrema → scala tympani → round window?
You’re making some instant ramen in your dorm kitchen when your roommate, who was coming back from CHEM0330 lab, very accidentally spills a mystery compound into your ramen. You’re a big fan of ramen so you eat it anyway, but it turns out the compound blocks all potassium channels in outer hair cells. Which aspect of hearing would be especially impaired, and what mechanism explains the deficit?
What is sensitivity to quiet sounds; outer hair cells normally amplify basilar membrane vibrations?
An experiment replaces the endolymph with a fluid whose ionic composition resembles perilymph. The tip links and transduction channels remain intact. Explain why auditory transduction would be impaired.
What is the electrochemical driving force for K⁺ entry would be reduced.
1) The encoding method for low frequency sounds.
2) The physical phenomenon exhibited by low frequency waves.
Hint: Why is there no sound shadow?
What is 1) interaural time delay and 2) diffraction?
1) The __ stream sends input to the __ lobe to process sound localization.
2) The __ stream sends input to the __ lobe to process complex sound identity.
What is 1) dorsal, parietal; 2) ventral, temporal?
Dr. Evil wants to stop the attenuation reflex in his nemesis what two muscles should he target? What will his victim no longer be able to do?
stapedius, and tensor tympani, attenuate sound
1) The fluid in the scala media.
2) The ion highly concentrated in this fluid.
3) The numerical value of the endocochlear potential.
4) The tissue that maintains the endocochlear potential.
What is 1) endolymph, 2) potassium, 3) +80 mV, and 4) the stria vascularis?
Two inner hair cells receive the same sound frequency, but Cell A depolarizes more strongly than Cell B. Why can Cell A produce a stronger auditory nerve response without generating action potentials itself? Describe a characteristic of each cell relative to the incoming sound that could explain this diference.
Greater depolarization leads to more Ca²⁺ influx and glutamate release, increasing auditory nerve firing.
Cell A may have a characteristic frequency closer to the sound’s frequency, causing a stronger response.
1) The nucleus encoding interaural intensity difference.
2) The anatomical brain area this nucleus resides in.
3) The type of input received by this nucleus from the contralateral ear.
What is 1) the lateral superior olive (LSO), 2) the medulla (in brainstem), and 3) inhibitory?
1) the thalamic nucleus that sends input to A1
2) the name of the nerve fibers that send this input
What is 1) the medial geniculate nucleus; 2) the acoustic radiation?