The　circuit　of　the　tail-withdrawal　reflex　in　Aplysia　opens　up　possibilities　to　construct　model　systems　allowing　researchers　to　effectively　investigate　simple　forms　of　learning　and　memory.　Using　the　Python　interface　of　the　NEURON　software,　we　simulated　this　reflex　circuit　and　studied　various　characteristics　of　the　latter.　The　phenomenon　of　spike　frequency　adaptation　(SFA)　and　the　period-adding　bifurcation　of　the　minimum　were　found　in　sensory　neurons,　when　the　latter　were　stimulated　by　square-wave　stimuli.　In　all　neurons　of　the　circuit,　variation　of　the　stimulus　strength　first　increased　and　then　decreased　the　number　of　spikes　in　a　burst.　In　addition,　with　decreases　in　the　number　of　stimulated　sensory　neurons,　a　subliminal　firing　other　than　that　in　an　intact　burst　appeared　at　the　outputs　of　interneurons　and　motor　neuron.　Moreover,　the　potentials　produced　in　the　motor　neuron　induced　corresponding　oscillations　of　the　muscle　fiber　force,　which　was　indicative　of　a　procedure　of　excitement-contraction　coupling　in　the　tail　part　of　Aplysia.　Finally,　upon　alteration　of　the　conductance　of　synapses　between　interneurons　and　motoneuron,　the　duration　of　long-lasting　responses　increased　regularly,　implying　synaptic　plasticity.