There remains a strong movement for Introductory Physics for Life Sciences (IPLS) courses to better integrate physics and biology. Part of the challenge for IPLS educators is to introduce fundamental physical law while simultaneously establishing the relevance of physics to biological science. Life science relevant laboratory experiences are essential to the training of future biologists and health professionals. The physiology of neurotransmission can be especially challenging to life science majors, but may be somewhat clarified in the IPLS course by model circuit labs. A realistic axon model lab using rubber tubing and gelatin recently reported by Dyer highlights the motivational value of lab experiences bridging biophysics and neurophysiology. Time-independent and time-dependent circuit labs modeling passive spread of charge within an axon absent the action potential have been described. In this paper, we describe a progressive complex circuit lab sequence introducing students to Kirchhoff's rules, a model of the cell membrane resting potential, and a model representing key features of the action potential in an axon. In this context, "complex" describes a circuit that cannot be reduced to a single battery and resistor.