Neural accommodation or neuronal accommodation occurs when a

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

cell is depolarised by slowly rising current ( ramp depolarisation) ''in vitro''. The

Hodgkin–Huxley model The Hodgkin–Huxley model, or conductance-based model, is a mathematical model that describes how action potentials in neurons are initiated and propagated. It is a set of nonlinear differential equations that approximates the electrical engine ...

also shows accommodation. Sudden depolarisation of a nerve evokes propagated

action potential An action potential (also known as a nerve impulse or "spike" when in a neuron) is a series of quick changes in voltage across a cell membrane. An action potential occurs when the membrane potential of a specific Cell (biology), cell rapidly ri ...

by activating voltage-gated fast

sodium channels Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na+) through a cell's membrane. They belong to the superfamily of cation channels. Classification They are classified into 2 types: Function In e ...

incorporated in the

cell membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...

if the depolarisation is strong enough to reach threshold. The open sodium channels allow more

sodium ion Sodium is a chemical element; it has symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isotope ...

s to flow into the cell and resulting in further depolarisation, which will subsequently open even more sodium channels. At a certain moment this process becomes regenerative (

vicious cycle A vicious circle (or cycle) is a complex chain of events that reinforces itself through a feedback loop, with detrimental results. It is a system with no tendency toward equilibrium (social, economic, ecological, etc.), at least in the short ...

) and results in the rapid ascending phase of action potential. In parallel with the depolarisation and sodium channel activation, the inactivation process of the sodium channels is also driven by depolarisation. Since the inactivation is much slower than the activation process, during the regenerative phase of action potential, inactivation is unable to prevent the "chain reaction"-like rapid increase in the membrane voltage. During neuronal accommodation, the slowly rising depolarisation drives the activation and inactivation, as well as the potassium gates simultaneously and never evokes action potential. Failure to evoke action potential by ramp depolarisation of any strength had been a great puzzle until Hodgkin and Huxley created their physical model of action potential. Later in their life they received a Nobel Prize for their influential discoveries. Neuronal accommodation can be explained in two ways. "First, during the passage of a constant cathodal current through the membrane, the potassium conductance and the degree of inactivation will rise, both factors raising the threshold. Secondly, the steady state ionic current at all strengths of depolarization is outward, so that an applied cathodal current which rises sufficiently slowly will never evoke a regenerative response from the membrane, and excitation will not occur." (quote from Hodgkin and Huxley) ''In vivo'' physiologic condition accommodation breaks down, that is long-duration slowly rising current excites nerve fibers at a nearly constant intensity no matter how slowly this intensity is approached.

References

External links

Interactive Java applet of the HH model
Parameters of the model can be changed as well as excitation parameters and phase space plottings of all the variables is possible.
Direct link to Hodgkin-Huxley model
and
Description
in

BioModels Database BioModels is a free and open-source repository for storing, exchanging and retrieving quantitative models of biological interest created in 2006. All the models in the curated section of BioModels Database have been described in peer-reviewed scie ...

* Direct link to Hodgkin-Huxley paper #1 via PubMedCentral * Direct link to Hodgkin-Huxley paper #2 via PubMedCentral * Direct link to Hodgkin-Huxley paper #3 via PubMedCentral * Direct link to Hodgkin-Huxley paper #4 via PubMedCentral * Direct link to Hodgkin-Huxley paper #5 via PubMedCentral
Neural Impulses: The Action Potential In Action
by Garrett Neske,

The Wolfram Demonstrations Project The Wolfram Demonstrations Project is an open-source collection of interactive programmes called Demonstrations. It is hosted by Wolfram Research. At its launch, it contained 1300 demonstrations but has grown to over 10,000. The site won a Pa ...

Interactive Hodgkin-Huxley model
by Shimon Marom,

ModelDB
A computational neuroscience source code database containing 4 versions (in different simulators) of the original Hodgkin–Huxley model and hundreds of models that apply the Hodgkin–Huxley model to other channels in many electrically excitable cell types. {{DEFAULTSORT:Hodgkin-Huxley Model Nonlinear systems Electrophysiology Ion channels Computational neuroscience

See also

References

External links