It is the electrical signal that nervous tissue generates for communication. A stronger stimulus will generally cause a cell to fire faster than a weaker stimulus will.Ĭarlson, N. What has been described here is the action potential, which is presented as a graph of voltage over time in Figure 12.5.7. Neurons, however, can provide information about the strength of a stimulus by altering the rate at which they generate action potentials. A weaker stimulus will not produce a weaker neural impulse. Once the cell depolarizes to the required threshold, the action potential. This means that some event (a stimulus) causes the resting potential to move toward 0 mV. Neurons follow an all-or-none principle, meaning that either the neuron fires an action potential or it does not fire one. As a result, sodium ions enter the action and change the polarization of the axon. The action potential is an explosion of electrical activity that is created by a depolarizing current. At the synapse, the action potential triggers the release of the neurotransmitter substance to affect postsynaptic cells. The action potential originates near the soma and once it starts, it travels down the entire length of the axon until it reaches the terminal buttons. At the peak of the action potential, the inside of the axon becomes less negative (or even positive), and potassium ions are driven out of the cell while positively charged sodium ions rush in. An action potential results from brief changes in the membrane's permeability to sodium and potassium ions. Action potential duration is relatively short 3-5 ms. Neurons fire according to the All-or-Nothing Principle, meaning that they will either fire completely or not at all. Duration of graded potentials may be a few milliseconds to seconds. Amplitude is generally small (a few mV to tens of mV). Stimulation of sufficient intensity alters the permeability of the cell membrane. Amplitude is all-or-none strength of the stimulus is coded in the frequency of all-or-none action potentials generated. Athabasca University Athabasca University Psychology Glossary of Termsīrief, localised, transient change in the neuron's voltage, providing the basis for the conduction of information along an axon.
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