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Postsynaptic potentials are changes in the membrane potential of the postsynaptic terminal of a chemical synapse. Postsynaptic potentials are graded potentials , and should not be confused with action potentials although their function is to initiate or inhibit action potentials.
In nature, myelinated segments are generally long enough for the passively propagated signal to travel for at least two nodes while retaining enough amplitude to fire an action potential at the second or third node. Thus, the safety factor of saltatory conduction is high, allowing transmission to bypass nodes in case of injury. However, action ...
The amplitude of one postsynaptic potential at the time point when the next one begins will algebraically summate with it, generating a larger potential than the individual potentials. This allows the membrane potential to reach the threshold to generate an action potential.
"Unitary connection" usually refers to an unknown number of individual synapses connecting a presynaptic neuron to a postsynaptic neuron. The amplitude of postsynaptic potentials (PSPs) can be as low as 0.4 mV to as high as 20 mV. [20] The amplitude of a PSP can be modulated by neuromodulators or can
where ′ is the firing times of neuron j (i.e., its spike train); () describes the time course of the spike and the spike after-potential for neuron i; and and (′) describe the amplitude and time course of an excitatory or inhibitory postsynaptic potential (PSP) caused by the spike ′ of the presynaptic neuron j.
Neurotransmitter release can be measured by determining the amplitude of the postsynaptic potential after triggering an action potential in the presynaptic neuron. Measuring neurotransmitter release this way can be problematic because the effect of the postsynaptic neuron to the same amount of released neurotransmitter can change over time.
Graded potentials that make the membrane potential more negative, and make the postsynaptic cell less likely to have an action potential, are called inhibitory post synaptic potentials (IPSPs). Hyperpolarization of membranes is caused by influx of Cl − or efflux of K +. As with EPSPs, the amplitude of the IPSP is directly proportional to the ...
Whether a postsynaptic potential is considered excitatory or inhibitory depends on the reversal potential for the ions of that current, and the threshold for the cell to fire an action potential (around –50mV). A postsynaptic current with a reversal potential above threshold, such as a typical Na + current, is