IHS Anatomy and Physiology of Hearing 4 — Questions and Answers
Question 1: The endocochlear potential (EP) in the scala media is approximately:
- +80 mV (Correct answer)
- -70 mV
- +10 mV
- -40 mV
Correct answer: +80 mV
The endocochlear potential is approximately +80 mV, created by the stria vascularis, and provides the driving force for K⁺ to enter hair cells during transduction.
Question 2: Otoacoustic emissions (OAEs) originate from:
- Inner hair cell depolarization
- Outer hair cell electromotility (Correct answer)
- Auditory nerve firing patterns
- Cochlear fluid movement only
Correct answer: Outer hair cell electromotility
OAEs are sounds generated by the active mechanical movements (electromotility) of outer hair cells and can be measured in the ear canal, reflecting cochlear health.
Question 3: Which ascending auditory pathway structure is primarily responsible for binaural processing and sound localization?
- Cochlear nucleus
- Superior olivary complex (Correct answer)
- Inferior colliculus
- Medial geniculate body
Correct answer: Superior olivary complex
The superior olivary complex is the first site where inputs from both ears converge, enabling interaural time and level difference processing for localization.
Question 4: Presbycusis (age-related hearing loss) predominantly affects hearing in which frequency range first?
- Low frequencies (250–500 Hz)
- Mid frequencies (1000–2000 Hz)
- High frequencies (4000–8000 Hz) (Correct answer)
- All frequencies equally
Correct answer: High frequencies (4000–8000 Hz)
Presbycusis typically begins with high-frequency loss because the cochlear base, which processes high frequencies, is most exposed to cumulative noise and metabolic stress.
Question 5: The round window membrane functions to:
- Amplify incoming sound pressure
- Allow perilymph displacement when the stapes moves (Correct answer)
- Produce perilymph
- Anchor the basilar membrane
Correct answer: Allow perilymph displacement when the stapes moves
The compliant round window membrane bulges outward into the middle ear when the stapes pushes inward, allowing cochlear fluid to move and the basilar membrane to vibrate.
Question 6: The traveling wave theory of cochlear mechanics was proposed by:
- Hermann von Helmholtz
- Georg von Békésy (Correct answer)
- Carl Wernicke
- Ernst Weber
Correct answer: Georg von Békésy
Georg von Békésy described the traveling wave along the basilar membrane, earning the 1961 Nobel Prize in Physiology or Medicine for this work.
Question 7: The medial geniculate body (MGB) relays auditory information to which cortical area?
- Primary somatosensory cortex (S1)
- Primary visual cortex (V1)
- Primary auditory cortex (A1) in the temporal lobe (Correct answer)
- Prefrontal cortex
Correct answer: Primary auditory cortex (A1) in the temporal lobe
The MGB, part of the thalamus, projects to primary auditory cortex (Heschl's gyrus) in the superior temporal lobe, the last subcortical relay in the ascending pathway.
IHS Anatomy and Physiology of Hearing 4
The endocochlear potential (EP) in the scala media is approximately: