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As an action potential (nerve impulse) travels down an axon there is a change in electric polarity across the membrane of the axon. In response to a signal from another neuron, sodium- (Na +) and potassium- (K +)–gated ion channels open and close as the membrane reaches its threshold potential.
An action potential initiated anywhere on an axon will travel in an antidromic (backward) direction to the neuron soma (cell body) without loss of amplitude and produce a full-amplitude action potential in the soma. As the membrane area of the soma is orders of magnitude larger than the area of the axon, conservation of energy requires that an ...
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 engineering characteristics of excitable cells such as neurons and muscle cells .
Stochastic spike generation (noisy output) depends on the momentary difference between the membrane potential V(t) and the threshold. The membrane potential V of the spike response model (SRM) has two contributions. [51] [52] First, input current I is filtered by a first filter k. Second the sequence of output spikes S(t) is filtered by a ...
Equivalent electrical circuit for the Hodgkin–Huxley model of the action potential. I m and V m represent the current through, and the voltage across, a small patch of membrane, respectively. The C m represents the capacitance of the membrane patch, whereas the four g's represent the conductances of four types of ions.
[1] [2] The Hodgkin–Huxley model also shows accommodation. [3] Sudden depolarisation of a nerve evokes propagated action potential by activating voltage-gated fast sodium channels incorporated in the cell membrane if the depolarisation is strong enough to reach threshold.
In addition to increasing the speed of the nerve impulse, the myelin sheath helps in reducing energy expenditure over the axon membrane as a whole, because the amount of sodium and potassium ions that need to be pumped to bring the concentrations back to the resting state following each action potential is decreased. [3]
The larger the membrane resistance , the harder it is for a current to induce a change in membrane potential. So the higher the τ {\displaystyle \tau } the slower the nerve impulse can travel. That means, membrane potential (voltage across the membrane) lags more behind current injections.