Bioethics Blogs

Snapshots of Life: The Biological Basis of Hearing

Credit: Peter Barr-Gillespie and Kateri Spinelli, Oregon Health & Science University, Portland

Did you know that chickens have ears? Well, here’s the evidence—you’re looking at a micrograph of sensory hair cells that make up the inner ear of Gallus gallus domesticus, otherwise known as the domestic chicken. Protruding from each hair cell is a tall bundle of stiff appendages, called stereocilia, that capture vibrations and enable the chicken to hear everything from grain being poured into a feeder to the footsteps of a wily fox. The flatter area is occupied by supporting cells, which have recently been shown to have the capacity to regenerate damaged or destroyed hair cells.

Peter Barr-Gillespie and Kateri Spinelli of Oregon Health & Science University, Portland used a scanning electron microscope to capture this image—one of the winners of the Federation of American Societies for Experimental Biology’s 2014 BioArt competition—while studying how these cells convert sound waves into brain waves. It is generally known that sound waves cause the stereocilia on each hair cell to oscillate in concert. These vibrating stereocilia trigger electrical changes in the hair cells, which then send signals to the brain. Barr-Gillespie’s group focuses on the actual molecules that build the stereocilia and translate the vibrations into brain signals.

Sensory hair cells are vital for hearing. But when you are crank up the volume on your MP3 player or use loud machinery, the powerful sound waves can break and sometimes snap off the stereocilia, eventually killing the hair cells.

In humans, the destruction of hair cells by noise exposure, injury, or disease can lead to permanent hearing loss, a problem that affects some 26 million Americans.

The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.