Question

If one synapse (A) is weakly stimulated (low frequency of action potential firing) repetitively for a few minutes, there is no change in EPSP magnitude. Now suppose a second synapse (B) on the same dendrite is stimulated at high frequency at the same time as synapse A is weakly stimulated. Minutes after the high frequency stimulation of synapse B, would you expect the EPSP on synapse A, measured after initiation of a single action potential, to have changed? Why or why not?

Answer 1

The EPSP on synapse A is expected to have changed minutes after the high frequency stimulation of synapse B. Synaptic summation and the threshold for excitation act as a filter, and multiple presynaptic inputs must create EPSPs around the same time to sufficiently depolarize the postsynaptic neuron to fire an action potential.

Step-by-step explanation:

The EPSP on synapse A, measured after initiation of a single action potential, is expected to have changed minutes after the high frequency stimulation of synapse B. This is because synaptic summation and the threshold for excitation act as a filter, and multiple presynaptic inputs must create EPSPs around the same time to sufficiently depolarize the postsynaptic neuron to fire an action potential. The high frequency stimulation of synapse B can help depolarize the postsynaptic neuron and increase the likelihood of reaching the threshold of excitation.