Chemical synapses are either ordepending on how they
affect the membrane potential of the post synaptic Neuron

there is a possibility that the neuron can fire back at the potential neuron.

Explanation:

At a chemical synapses an action of potential triggers the Presynaptic neuron to the postsynaptic neuron either more or less likely to fire its own action of its potential neuron.

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explanation:

evolution theory