What is the function of stereocilia?

• A. Movement of material along the apical surface
• B. Secretion of mucus
• C. Detection of mechanical stimuli
• D. Anchoring to basement membrane

Answer: (C)

Stereocilia function as mechanosensors on hair cells of the inner ear. These actin-filled, hair-like projections don’t beat themselves; instead, when they are bent by sound vibrations or head movements, the deflection pulls tip links that open mechanically gated ion channels. This causes a rush of ions into the hair cell, depolarizing it and leading to neurotransmitter release to the auditory or vestibular nerves. This mechanical-to-electrical signal is how we hear and maintain balance. They are not involved in moving material along a surface, secreting mucus, or anchoring to the basement membrane, which is why the other options don’t fit.