Vibration (Organ of Corti - the inner ear)
In the collection of Decibel Therapeutics, Boston, MA.
15" hs x 26" w
A man lies, unmoving. How do we tell if he is alive? The answer is "vibration" - the beat of the heart, the regular intake of breath. How do most life forms communicate? Vibrating light waves that strike the retina (or analogous structure), or sound waves which strike the Organ of Corti (shown in this work) in our inner ear which converts them into another form of vibration - nerve impulses. And how does the brain interpret these?
Sound waves reaching the inner ear cause vibration of the tectorial membrane (green). Three rows of outer hair cells and one row of inner hair cells (red) carry stereocilia - hair like structures which slide with respect to each other as a result of these vibrations. This sliding, pulls on thread-like “tip links” (visible only with electron microscopy, composed of proteins known as cadherins) which connect the stereocilia to each other. The pulling on the tip-links opens tension controlled ion channels in the hair cells, and the resultant movement of ions, including calcium, into the hair cells triggers them to release neurotransmitters at their base. These chemical signals activate nerves (blue) to send signals which the brain eventually interprets as sound. Ion channels in neighboring cells include gap junctions composed of "connexin" proteins. These ion channels aid in restoring the balance of ions caused by the movements of calcium and potassium into hair cells. Defects in these connexin proteins due to mutation are the basis of a major inherited form of deafness, while other inherited forms of deafness may be associated with other components of the organ of Corti. Deafness has also been associated with loss of hair cells, and one therapeutic approach is to find ways to regenerate the hair cells.
This work was inspired by a senior seminar course I taught - Medical Genetics - which focused on three inherited diseases, one of which was connexin-associated deafness, and by a guest speaker who spoke to the class, through interpreters, about what it was like to grow up deaf.