Soliton model

Soliton model

The Soliton model in neuroscience is a recently developed model that attempts to explain how signals are conducted within neurons. It proposes that the signals travel along the cell's membrane in the form of certain kinds of sound (or density) pulses known as solitons. As such the model presents a direct challenge to the widely accepted Hodgkin-Huxley model which proposes that signals travel as action potentials: voltage-gated ion channels in the membrane open and allow ions to rush into the cell, thereby leading to the opening of other nearby ion channels and thus propagating the signal in an essentially electrical manner.

History

The Soliton model was developed beginning in 2005 by Thomas Heimburg and Andrew D. Jackson, both at the Niels Bohr Institute of the University of Copenhagen. Heimburg heads the institute's Membrane Biophysics Group and as of early 2007 all published articles on the model come from this group.

Justification

The model starts with the observation that cell membranes always have a freezing point (the temperature below which the consistency changes from fluid to gel-like) only slightly below the organism's body temperature, and this allows for the propagation of solitons. It has been known for several decades that an action potential traveling along a neuron results in a slight increase in temperature followed by a decrease in temperature. The decrease is not explained by the Hodgkin-Huxley model (electrical charges traveling through a resistor always "produce" heat), but traveling solitons do not lose energy in this way and the observed temperature profile is consistent with the Soliton model. Further, it has been observed that a signal traveling along a neuron results in a slight local thickening of the membrane and a force acting outwards; this effect is not explained by the Hodgkin-Huxley model but is clearly consistent with the Soliton model.

It is undeniable that an electrical signal can be observed when an action potential propagates along a neuron. The Soliton model explains this as follows: the traveling soliton locally changes density and thickness of the membrane, and since the membrane contains many charged and polar substances, this will result in an electrical effect, akin to piezoelectricity.

Application

The authors claim that their model explains the previously obscure mode of action of numerous anesthetics. The Meyer-Overton observation holds that the strength of a wide variety of chemically diverse anesthetics is proportional to their lipid solubility, suggesting that they do not act by binding to specific proteins such as ion channels but instead by dissolving in and changing the properties of the lipid membrane. Dissolving substances in the membrane lowers the membrane's freezing point, and the resulting larger difference between body temperature and freezing point inhibits the propagation of solitons. By increasing pressure, lowering pH or lowering temperature, this difference can be restored back to normal, which should cancel the action of anesthetics: this is indeed observed. The amount of pressure needed to cancel the action of an anesthetic of a given lipid solubility can be computed from the soliton model and agrees reasonably well with experimental observations.

ee also

*Biological neuron models
*Hodgkin-Huxley model
*Memristor

ources

* [http://www.ku.dk/english/news/?content=http://www.ku.dk/english/news/nerve_soundtrack.htm On the (sound) track of anesthetics] , press release University of Copenhagen, 6 March 2007
* Kaare Græsbøll. [http://www.gamma.nbi.dk/Galleri/gamma143/nerves.pdf Function of Nerves - Action of Anesthetics] , Gamma 143, 2006. An elementary introduction.
* Thomas Heimburg, Andrew D. Jackson. [http://www.pnas.org/cgi/content/full/102/28/9790 On soliton propagation in biomembranes and nerves.] "PNAS", vol 102, no. 2. 12 July 2005
* Thomas Heimburg, Andrew D. Jackson. [http://arxiv.org/abs/physics/0610117 On the action potential as a propagating density pulse and the role of anesthetics.] Preprint, October 2006.
* Thomas Heimburg, Andrew D. Jackson. [http://www.biophysj.org/cgi/rapidpdf/biophysj.106.099754v1 The thermodynamics of general anesthesia.] "Biophysical Journal", 9 February 2007
* Pradip Das, W. H. Schwarz. [http://link.aps.org/abstract/PRE/v51/p3588 Solitons in cell membrane.] "Physics Review E", 4 November 1994


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Soliton — In mathematics and physics, a soliton is a self reinforcing solitary wave (a wave packet or pulse) that maintains its shape while it travels at constant speed. Solitons are caused by a cancellation of nonlinear and dispersive effects in the… …   Wikipedia

  • Soliton (optics) — In optics, the term soliton is used to refer to any optical field that does not change during propagation because of a delicate balance between nonlinear and linear effects in the medium. There are two main kinds of solitons: spatial solitons:… …   Wikipedia

  • Dissipative soliton — Dissipative solitons (DSs) are stable solitary localized structures that arise in nonlinear spatially extended dissipative systems due to mechanisms of self organization. They can be considered as an extension of the classical soliton concept in… …   Wikipedia

  • Vector soliton — Among all the soliton considered, the optical soliton draws the most attention as it is possible to generate ultrafast pulses and has wider application. optical soliton can be classified as two groups:temporal soliton and spatial soliton.however …   Wikipedia

  • Biological neuron model — A biological neuron model (also known as spiking neuron model) is a mathematical description of the properties of nerve cells, or neurons, that is designed to accurately describe and predict biological processes. This is in contrast to the… …   Wikipedia

  • Hodgkin–Huxley model — Basic components of Hodgkin–Huxley type models. Hodgkin–Huxley type models represent the biophysical characteristic of cell membranes. The lipid bilayer is represented as a capacitance (Cm). Voltage gated and leak ion channels are represented by… …   Wikipedia

  • Non-topological soliton — In quantum field theory, a non topological soliton (NTS) is a field configuration possessing, contrary to a topological one, a conserved Noether charge and stable against transformation into usual particles of this field for the following reason …   Wikipedia

  • Davydov soliton — Side view of an α helix of alanine residues in atomic detail. Protein α helices provide substrate for Davydov soliton creation and propagation. Davydov soliton is a quantum quasiparticle representing an excitation propagating along the protein α… …   Wikipedia

  • Global climate model — AGCM redirects here. For Italian competition regulator, see Autorità Garante della Concorrenza e del Mercato. Climate models are systems of differential equations based on the basic laws of physics, fluid motion, and chemistry. To “run” a model,… …   Wikipedia

  • Non-linear sigma model — In quantum field theory, a nonlinear σ model describes a scalar field Σ which takes on values in a nonlinear manifold called the target manifold T. The target manifold is equipped with a Riemannian metric g. Σ is a differentiable map from… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”