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What roles do inner hair cells and outer hair cells have in hearing?

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Compound eye — Senses Vespid wasps (Vespidae), similar to other insects, have compound eyes that consist of thousands of tiny optical units known as ommatidia, which contain light-sensitive photoreceptor cells.

Within the organ of Corti, inner hair cells and outer hair cells serve distinct but complementary roles in the process of hearing:

Inner Hair Cells: These cells are the primary sensory receptors. They receive the majority of afferent nerve endings—approximately 95 percent of the fibres in the cochlear nerve—and are responsible for transmitting electrical signals to the brainstem.12
Outer Hair Cells: These cells function as mechanical-electrical stimulators and feedback elements. Containing contractile proteins like actin and myosin, they can contract rhythmically in response to sound, which is believed to modify and enhance the discriminatory responses of the inner hair cells. By acting as tuned structures, they help sensitize the cochlea to low-level sounds; their destruction can significantly elevate hearing thresholds.1

While inner hair cells are uniform in size and arranged in a single row, outer hair cells are smaller, more numerous, and arranged in multiple rows, often sharing nerve fibre connections. Together, these cells transduce mechanical vibrations into nerve impulses, a process essential for auditory perception.12