Mechanical modeling of vestibular hair cell bundles

Abstract

Hair cells are transducers found found in the inner ear of vertebrates. They convert a mechanical signal, detected by the deflection of a bundle of cilia extending from their top surface, into an electrochemical signal. This dissertation studies the mechanical influence of the structure and materials on the function of the cells.

I introduce two methods to conduct the mechanical analysis. The first uses strength of materials formulae to solve the simplified hair cell bundle models. The second is a finite element analysis, used to better account for the observed complexity of the structure.

I then use these two techniques to build a fundamental understanding of the hair cell bundle structure. By first studying simplified models, then adding complexity, the effects of geometric and material variation can be deduced.

I then study three actual bundles. These are all taken from vestibular organs of turtles, two from the posterior semicircular canal and one from the utricle. I present estimations of stiffness, tip link tensions, and nonlinear response.

Finally, I investigate a single cilium forced by a fluid flow. The problem is solved by finite difference technique. Three different initial conditions are solved.