The Journal of Membrane Biology

, Volume 209, Issue 2, pp 135–152

Electromechanical Models of the Outer Hair Cell Composite Membrane

  • A. A. Spector
  • N. Deo
  • K. Grosh
  • J. T. Ratnanather
  • R. M. Raphael
Article

DOI: 10.1007/s00232-005-0843-7

Cite this article as:
Spector, A.A., Deo, N., Grosh, K. et al. J Membrane Biol (2006) 209: 135. doi:10.1007/s00232-005-0843-7

Abstract

The outer hair cell (OHC) is an extremely specialized cell and its proper functioning is essential for normal mammalian hearing. This article reviews recent developments in theoretical modeling that have increased our knowledge of the operation of this fascinating cell. The earliest models aimed at capturing experimental observations on voltage-induced cellular length changes and capacitance were based on isotropic elasticity and a two-state Boltzmann function. Recent advances in modeling based on the thermodynamics of orthotropic electroelastic materials better capture the cell’s voltage-dependent stiffness, capacitance, interaction with its environment and ability to generate force at high frequencies. While complete models are crucial, simpler continuum models can be derived that retain fidelity over small changes in transmembrane voltage and strains occurring in vivo. By its function in the cochlea, the OHC behaves like a piezoelectric-like actuator, and the main cellular features can be described by piezoelectric models. However, a finer characterization of the cell’s composite wall requires understanding the local mechanical and electrical fields. One of the key questions is the relative contribution of the in-plane and bending modes of electromechanical strains and forces (moments). The latter mode is associated with the flexoelectric effect in curved membranes. New data, including a novel experiment with tethers pulled from the cell membrane, can help in estimating the role of different modes of electromechanical coupling. Despite considerable progress, many problems still confound modelers. Thus, this article will conclude with a discussion of unanswered questions and highlight directions for future research.

Keywords

Piezoelectricity Prestin Cochlear amplifier Nonlinear capacitance Voltage-dependent stiffness Membrane curvature Cell mechanics Hearing Thermodynamics 

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • A. A. Spector
    • 1
  • N. Deo
    • 2
  • K. Grosh
    • 2
  • J. T. Ratnanather
    • 3
  • R. M. Raphael
    • 4
  1. 1.Department of Biomedical EngineeringJohns Hopkins University School of MedicineBaltimoreUSA
  2. 2.Department of Mechanical Engineering and Department of Biomedical EngineeringUniversity of MichiganAnn ArborUSA
  3. 3.Center for Imaging Science and Institute for Computational Medicine, Department of Biomedical EngineeringThe Johns Hopkins UniversityBaltimoreUSA
  4. 4.Department of Bioengineering, MS 142Rice UniversityHoustonUSA