To help students master challenging, threshold concepts in physiology, I used the flipped learning model in a human anatomy and physiology course with very encouraging results in terms of student motivation, preparedness, engagement, and performance. The flipped learning model was enhanced by pre-training and formative assessments that provided opportunities for retrieval practice. Students in flipped learning sections had much higher retention and pass rates than those in non-flipped learning sections. Students also achieved preset benchmarks for factual and procedural knowledge while falling slightly short for conceptual knowledge. I found that the flipped learning model effectively addresses the cognitive load involved in learning physiology, which typically has a high cognitive load. By lowering extraneous cognitive load via intentional content, managing intrinsic cognitive load via pre-training and retrieval practice, and increasing germane cognitive load via the extended class time reserved for problem solving, the flipped learning model offers a very supportive learning environment with numerous opportunities for self-regulated learning for students struggling to master this threshold concept. In future semesters, the increased available class time afforded by the flipped learning format will be used to emphasize conceptual understanding in the problem sets.