2005 APS March Meeting
Monday–Friday, March 21–25, 2005;
Los Angeles, CA
Session B22: Focus Session: Fluctuations and Fluctuation Analysis in Biological Systems
11:15 AM–1:51 PM,
Monday, March 21, 2005
LACC
Room: 409B
Sponsoring
Unit:
DBP
Chair: Peter Hanggi, University Augsburg
Abstract ID: BAPS.2005.MAR.B22.1
Abstract: B22.00001 : Stochastic signalling in excitable ion channel clusters
11:15 AM–11:51 AM
Preview Abstract
Abstract
Author:
Gerhard Schmid
(University of Augsburg, 86135 Augsburg, Germany)
The electric properties of axonal cell membranes are
predominantly determined by the dynamics of the voltage-dependent
gating of potassium and sodium ion channels. The inherent
stochastic dynamics of the gating process generates the so-called
channel noise. These fluctuations of the number of open ion
channels initiate spontaneous excitations. By use of a stochastic
generalization of the Hodgkin-Huxley model we investigate the
dependency of the spike production on the number of ion channels
within a cluster. There exist an optimal cluster size for which
solely the internal noise causes a most regular spontaneous
generation of action potentials -- the effect of intrinsic
coherence resonance -- and an optimal system size induced
Stochastic Resonance in presence of external driving [1,2]. In
addition to the variation of the size of ion channel clusters, the
living organisms may adopt the densities of different ion channels
in order to regulate the spontaneous spiking activity. We vary the
densities, i.e. the number of the specific ion channels for a
given membrane patch size by poisoning the potassium, or the
sodium ion channels yielding either an increase or decrease of the
regularity of the spiking dynamics [3].\\
We also investigate the influence of the gating charge on
spontaneous spiking: the ion channels contribute to the membrane
capacity, since the switching of the channel gates between an open
and a closed configuration is always connected with charge movement
within the cell membrane. Especially, for the case of relatively
large densities of ion channels (such as in nodes of Ranvier), this
may play a crucial role for nerve excitation. Surprisingly, the
gating charge do not dramatically change the excitation behavior.
This even holds true even for extremely dense ion channel
assemblies; instead the membrane capacity at rest exhibits a
bell-shaped dependence on the ion channel density. \\
\noindent [1] G. Schmid, I. Goychuk and P. H\"anggi, Europhys.
Lett {\bf 56}, 22 (2001).\\
\noindent [2] G. Schmid, I. Goychuk, P. H\"anggi, S. Zeng, and P.
Jung, Fluct. Noise Lett. {\bf 4}, L33 (2004).\\
\noindent [3] G. Schmid, I. Goychuk, and P. H\"anggi, Physical
Biology {\bf 1}, 61 (2004).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2005.MAR.B22.1