Duke Physics Colloquium: Making an effort to listen: mechanical amplification by ion channels and myosin molecules in hair cells of the inner ear

"Making an effort to listen: mechanical amplification by ion channels and myosin molecules in hair cells of the inner ear" - Human hearing is enhanced by an active process that amplifies the ear's mechanical inputs several hundredfold, sharpens frequency tuning to allow the discrimination of tones differing in frequency by only 0.2 %, and compresses six orders of magnitude in the amplitude of sounds into only two orders of magnitude in output. In addition, spontaneous otoacoustic emissions emerge from ears in a very quiet environment, an indication that the active process can be so exuberant as to become unstable. Cooperativity between mechanoelectrical-transduction channels confers negative stiffness on the hair bundle, which together with myosin-based adaptation motors elicits a dynamical instability that underlies the active process. Experiments on individual hair bundles indicate that the bundle's operation near this instability, a Hopf bifurcation, accounts for the four characteristics of the active process. Faculty Host: Henry Greenside. Coffee and cookies will be served before the event in room 128.