Berlin 2005 – scientific programme
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AKB: Biologische Physik
AKB 75: Nonlinear Phenomena and Pattern Formation
AKB 75.2: Talk
Wednesday, March 9, 2005, 10:45–11:00, TU H2013
Role of fluctuations in active hair-bundle mechanics — •Björn Nadrowski1, Pascal Martin2, and Frank Jülicher1 — 1Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Stra"se 38, 01309 Dresden — 2Laboratoire Physico-Chimie Curie, Unité Mixte de Recherche 168, Institut Curie, 26 rue d’Ulm, F-75248 Paris Cedex 05, France
Hearing relies on active filtering to achieve exquisite sensitivity and sharp frequency selectivity. In a quiet environment, the ears of many vertebrates emit one to several tones. These spontaneous otoacoustic emissions, the most striking manifestation of the inner ear’s active process, result from self-sustained mechanical oscillations of aural constituents.
It has been shown that the mechanosensitive hair bundles of vestibular cells from the frog ear have the ability to oscillate spontaneously. This spontaneous oscillation leads to frequency-selective amplification and nonlinearity in the bundles mechanical response.
We discuss the physical principles underlying detection based on critical oscillation as well as specific mechanisms that can lead to oscillations and active behaviors by hair bundles. A simple description of active hair-bundle mechanics is presented. We present the state diagram and show that fluctuations influence the mechanical response functions. We discuss different sources of fluctuations and estimate their influence on the hair-bundle’s mechanical properties. Furthermore, the linear and nonlinear response functions calculated numerically can quantitatively account for the observed properties of active hair-bundles.
Nadrowski, Martin, Julicher, PNAS 101, 12195 (2004)