Question

Otoacoustic emissions arise from:

• A. Inner hair cells
• B. Outer hair cells
• C. Organ of Corti
• D. Both outer and inner hair cells

Hint:

Think about which cochlear cells are motile and act as the cochlear amplifier, the basis of newborn hearing screening.

Answer 1

The Correct Option is B

Step 1: Otoacoustic emissions (OAEs) are low-level sounds produced by the cochlea and recorded in the external ear canal with a sensitive microphone. They reflect the active mechanical process happening inside the cochlea.
Step 2: The cochlea has two types of hair cells. Inner hair cells are the true sensory receptors that send signals up the auditory nerve. Outer hair cells are motile and act as a built-in amplifier, the so-called cochlear amplifier.
Step 3: When outer hair cells contract and expand in response to sound, they generate mechanical energy that travels back out through the middle ear. This back-travelling energy is the source of OAEs.
Step 4: So OAEs specifically test outer hair cell function. They are absent when outer hair cells are damaged, which is why OAEs are used for newborn hearing screening.
Step 5: Inner hair cells (A) generate the afferent nerve signal, not the emission. Organ of Corti (C) is the whole structure, too broad to be the specific source. Option D is wrong because inner hair cells do not produce the emission.
Hence the answer is Option B: Outer hair cells.