![]() ![]() Features of graded potentials and action potentials Graded potentialsĭepending on the stimulus, graded potentials can be depolarizing or hyperpolarizing.Īction potentials always lead to depolarization of membrane and reversal of the membrane potential.Īmplitude is proportional to the strength of the stimulus.Īmplitude is all-or-none strength of the stimulus is coded in the frequency of all-or-none action potentials generated.Īmplitude is generally small (a few mV to tens of mV).ĭuration of graded potentials may be a few milliseconds to seconds.Īction potential duration is relatively short 3-5 ms. ![]() In yet another later lecture, we will see how summation of graded potentials is responsible for much of information processing at specialized contact regions between neurons (synapses). In the next lecture, we will consider the propagation of neuronal action potentials and we will see that additional neuronal adaptations allow action potentials to travel over long distances without losing any strength (i.e., amplitude). These graded potentials will be discussed in later lectures. Depending on the cell and type and the nature of stimulus, graded potentials that lead to action potentials are called synaptic potentials (i.e., post-synaptic potential changes in neurons), generator potentials or receptor potentials (graded potentials in sensory cells causes by adequate stimuli), or end-plate potentials (i.e., synaptic potentials in skeletal muscle cells). Graded potentials must occur to depolarize the neuron to threshold before action potentials can occur. As discussed in this lecture and upcoming lectures, most of these differences are due to the fact that graded potentials result from the passive electrical property of the neuronal membrane, whereas action potentials result from an orchestrated response to depolarizing stimuli, and involve a coordinated activity of voltage-gated ion channels. Table 1 lists the main differences between graded potentials and action potentials. There are important differences between graded potentials and action potentials of neurons (see Introduction to this lecture). ![]()
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