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As an example, the cardiac action potential illustrates how differently shaped action potentials can be generated on membranes with voltage-sensitive calcium channels and different types of sodium/potassium channels. The second type of mathematical model is a simplification of the first type; the goal is not to reproduce the experimental data ...
Feedforward inputs that form synapses proximal to the soma and directly lead to action potentials; NMDA spikes generated in the more distal basal; Apical dendrites that depolarize the soma (usually insufficient to generate a somatic action potential) - Learns by growing new synapses - Inspired by the pyramidal cells in neocortex layers 2/3 and 5
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 rapidly rises and falls. [1] This depolarization then causes adjacent locations to similarly depolarize.
The actual physiological potential depends on the ratio of the reduced (Red) and oxidized (Ox) forms according to the Nernst equation and the thermal voltage. When an oxidizer ( Ox ) accepts a number z of electrons ( e − ) to be converted in its reduced form ( Red ), the half-reaction is expressed as:
For a derivation of the Hodgkin–Huxley equations under voltage-clamp, see. [3] Briefly, when the membrane potential is held at a constant value (i.e., with a voltage clamp), for each value of the membrane potential the nonlinear gating equations reduce to equations of the form:
A Cartesian coordinate system is used to describe the system, with the z direction being perpendicular to the membrane. Assuming that the system is symmetrical in the x and y directions (around and along the axon, respectively), only the z direction need be considered; thus, the voltage E m is the integral of the z component of the electric ...
The slope of phase 0 on the action potential waveform (see figure 2) represents the maximum rate of voltage change of the cardiac action potential and is known as dV/dt max. In pacemaker cells (e.g. sinoatrial node cells ), however, the increase in membrane voltage is mainly due to activation of L-type calcium channels.
The strength-duration time constant (chronaxie) and rheobase are parameters that describe the strength-duration curve—the curve that relates the intensity of a threshold stimulus to its duration. As the duration of a test stimulus increases, the strength of the current required to activate a single fiber action potential decreases.