Mechanical modelling of vestibular hair cell’s amplifying mechanism.

Abstract

INTRODUCTION: Vestibular hair cell is the basic sensory unit of nature’s inertia sensor. It has high sensitivity over broad dynamic range by combination of negative stiffness and adaptation mechanism.[1][2] To examine these biophysical mechanisms with a mechanical point of view[3], we developed a mechanical model of vestibular hair cell. We measure the system response and stiffness and observe similar characteristics with hair cell. This results help to better understanding of vestibular hair cell function.

METHODS: A mechanical model of stereocilia on hair cell consists of two inverted pendulums that demonstrate a pair of adjacent stereocilia. To make negative stiffness which induced by a transduction channels’ sudden opening, use pair of magnet which make repulsive force. Adaptation mechanism is mimicked by using stepping motor similar with molecular motor on stereocilia. Stiffness and temporal response was measured using force sensor and motion capture system.

RESULTS: Similar results from physiological stereocilia were observed. Negative stiffness region was observed near the origin and this region was shifted as motor made magnet moving side-to-side. And the spontaneous oscillation which known to induced by the interplay of the negative stiffness and the adaptation of the stereocilia also observed. Parameter study of the model well demonstrated the role of each system component.

CONCLUSIONS: Integration of adaptation and negative stiffness mechanism of hair cell was mechanically mimicked by two inverted pendulums and interacting moving magnet pair controlled by stepping motor and results is similar to the physiological measurement.

ACKNOWLEDGEMENTS: The work was supported by the Pioneer Research Program fund of the Ministry of Education, Science and Technology.

Fig.1 Mechanical model of hair cell and force-displacement relation & time response of vestibular hair cell model.

REFERENCES

1. P.Martin. et al. PNAS. Vol.97, No.22, pp.12026-12031. 2000. 2. Peter G. Gillespie & Richard G. Walker. NATURE, Vol.413, 13. 2001. 3. Koeun Lim, Sukyung Park. Journal of Biomechanics. 42, 2158-2164. 2009.