Figure 5. Model representing hypothesized myogenic and neurogenic mechanisms for pumping control.

In intact worms, the activity of the MC neurons entrains the pharyngeal muscle and overrides the myogenic rhythm to cause rapid neurogenic pumping. When MC activity or postsynaptic response to MC activity is decreased, the myogenic rhythm sets the pumping rate. In the acute absence of nervous system function, pumping ceases completely. ACh represents acetylcholine. Circles with enclosed waveforms represent oscillators. Elements in gray are inactive.