Energy output from a single outer hair cell

TL;DR

This paper develops a simple dynamic model of outer hair cell electromotility, revealing how mechanical load and viscous drag influence energy output, with viscous drag playing a more significant role in receptor potential enhancement.

Contribution

Introduces a one-dimensional dynamic model of outer hair cell electromotility that accounts for load, drag, and mass effects, providing analytical insights into energy output mechanisms.

Findings

Viscous drag more effectively enhances receptor potential than elastic load.

OHCs are more effective in counteracting viscous drag than supplying elastic energy.

Derived an analytical expression for membrane capacitance dependent on mechanical load.

Abstract

Electromotility of outer hair cells (OHCs) has been extensively studied with in vitro experiments because of its physiological significance in the cochlear amplifier, which provides the exquisite sensitivity and frequency selectivity of the mammalian ear. However, these studies have been performed largely under load-free conditions or with static load, while these cells function in vivo in a dynamic environment, receiving electrical energy to enhance mechanical oscillation in the inner ear. This gap leaves uncertainties in addressing a key issue, how much mechanical energy an OHC provides. The present report is an attempt of bridging the gap by introducing a simple one-dimensional model for electromotility of OHC in a dynamic environment. This model incorporates a feedback loop involving the receptor potential and the mechanical load on OHC, and leads to an analytical expression for the membrane capacitance, which explicitly describes the dependence on the elastic load, viscous drag, and the mass. The derived equation of motion was examined in a mass-less model system with realistic parameter values for OHC. It was found that viscous drag is more effective than elastic load in enhancing the receptor potential that drives the cell. For this reason, it is expected that OHCs are more effective in counteracting viscous drag than providing elastic energy to the system.