Question

Temporal Summation

why do many stimuli sent in rapid succession cause a contraction when a single sub threshold stimulus fails ?

Answer 1

• Temporal summation is the rapid succession of action potentials in a presynaptic neuron, where the resultant (An excitatory postsynaptic potential) EPSPs is monitored.
• Two action potentials in rapid succession create two EPSPs, but the important point to note that the second EPSP occurs during the falling phase of the first, and the depolarization associated with the second EPSP which adds to the depolarization produced by the first.
• Thus, two action potentials create a summated potential of around 2 mV in amplitude. Three action potentials in rapid succession would create a summated potential of about 3 mV. Thus, potentials in quick succession will create enough potential and easily provide the cell to threshold point required.