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Details of How we hear

How hearing takes place at the molecular level.

Researchers have long known that hair cells, small sensory cells in the inner ear, convert sound energy into electrical signals that travel to the brain, a process called mechanotransduction.

However, the closer one zooms in on the structures involved, the murkier our understanding becomes.

When fluid in the inner ear is set into motion by vibrations emanating from the bones of the middle ear, the rippling effect causes bristly structures atop the hair cells to bump up against an overlying membrane and to deflect.

Like seats in a three-row stadium, the bristles, called stereocilia, are arranged in tiers, with each lower seat connected to a higher seat by minute, threadlike bridges, or links.

As the stereocilia are deflected, pore-like channels on the surface of the stereocilia open up, allowing potassium to rush in, and generating an electrical signal.

Because the "tip link" -- the link that connects the tip of the shorter stereocilium to the side of the adjacent, taller stereocilium -- must be present for the channel to function, scientists believe that this structure may be responsible for opening and closing the channel gate.

Researchers suggest that if they can learn the makeup of the tip link, they'll be that much closer to understanding how the gate mechanism operates.

National Institutes of Health

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