One amazing aspect of physiology is the coordinated, almost choreographed function of millions of moving parts.  The body has mastered multitasking, maintaining hundreds of parameters within narrow and optimal ranges at the same time.  This very aspect of physiology fuels our passion and enthusiasm for teaching physiology and piques the interests of students.  The networks of numerous overt and subtle interdependent mechanisms and signaling pathways between multiple organs and tissues that regulate plasma calcium or energy intake, for example, also represent major challenges to understanding and learning physiology for students.  We ask our students to combine the wisdom of two old sayings: “You can’t see the forest for the trees’, and “The devil is in the details.”  They need to understand both the bigger picture of the whole animal and the nuanced interlinking of mechanisms, and even molecules, that seamlessly and dynamically maintain different parameters within narrow ranges.  It can be frustrating and discouraging for students.  Furthermore, passing with high marks in systems physiology or anatomy-physiology II is a criterion for eligibility to apply to various health profession programs.  As educators we must acknowledge the complexity of physiology and find ways to help our students literally see and master smaller sections of the larger regulatory network so they can recreate and master the larger network.

For even the best prepared student, as well as the student who cannot take all recommended prerequisite courses for A&P-II or basic physiology, the collection of numerous parts, mechanisms, equations and connections, principles, and laws can represent an obstacle to learning.  Student comments such as, “There is so much to know.”, “It’s so complicated.”, and “Physiology is hard.” are accurate and fair, but also warrant validation.  A little bit of validation and communicating the challenges we encountered as students goes a long way in helping our students’ willingness to endure and continue to strive.  Physiology courses are not impossible, but they are difficult and might well be the most difficult courses a student takes.  I will not pretend or lie to my students.  If I were to dismiss physiology as a whole or a given concept as easy and simple, I risk my student thinking they should be learning principles effortlessly or instinctively and begin to doubt themselves and give up.  It helps to confess apprehensions you yourself felt when first learning various physiological concepts or phenomena.  As a novice physiology student, I had many moments at which I wanted to tap out.  ne major example was my introduction to the beautiful, albeit daunting display of all the electrical and mechanical events that occur in only the heart during a single cardiac cycle in just 0.8 seconds, i.e., the Wiggers diagram.  Every time I project this diagram on the screen, I give students a moment to take it in and listen for the gasps or moans.  I admit to my students that upon seeing that diagram for the first time I looked for the nearest exit and thought to myself, ‘Are you kiddin’ me?”  Students laugh nervously.  They sigh in relief when I tell them that my professor broke down the diagram one panel at a time before putting all together; his approached worked, and that is what I will do for them.  Dr. Carl Wiggers was committed to teaching physiology and developed the diagram over 100 years ago as a teaching tool for medical students (1).  The diagram is instrumental in teaching normal cardiac physiology, as well as pathophysiology of congenital valve abnormalities and septal defects.  Nevertheless, students still need help to understand the diagram.  Again, here an example of the function of just one organ, the heart, being a central element to a larger network that regulates a major parameter – blood pressure.  Learning regulation of blood pressure can be an uphill battle for many students.

Cardiovascular physiology is typically a single unit in an undergraduate physiology course, and it is often the most challenging and difficult exam of the semester.  Several years ago, when preparing to teach this section in an AP-II course I felt compelled to find ways to help students break-down and reconstruct pieces of complex regulation of blood pressure.  I considered the many high-tech digital learning resources and online videos available to our students but wondered whether those resources help or hinder students.  I was also looking for tools that would facilitate multisensory learning, which is shown to yield better memory and recall (2).  Despite all these high-tech resources, I noticed students were still avid users of notecards and were convinced they held the secret to success in AP-I and thus, must also be the key to success in AP-II or systems physiology.  I found this quite amusing, because we used notecards back when I was in college in the 80s – when there were no digital learning platforms and highlighters only came in yellow.  Students tote around stacks of hand-written, color coded notecards that grow taller as the semester progresses, but often their comprehension and ability to connect one concept or mechanism to the next does not increase with the height of the stack.  Students often memorize terms on note cards but cannot readily connect the mechanism listed on one card to that on the next card or explain the consequence of that mechanism failing.  Around this time a non-science colleague was talking to me about her successful use of concept maps with her students.  To me, concept maps look a lot like biochemical pathways or physiological network diagrams.  It dawned on me.  I did not need to reinvent the wheel or make a newer better teaching tool.  I simply needed to help my students connect The Notecards and practice arranging them to better pattern regulatory networks.  Students were already writing a term on one side of the card and a definition and other notes on the back.  Why not build on that activity and more deliberately guide students to use cards to build a concept map of the network for regulation of blood pressure which is central to cardiovascular physiology?

Blood pressure is a physiological endpoint regulated by a nexus of autoregulatory, neural and hormonal mechanisms and multiple organs and tissues.  Blood pressure is directly dependent on cardiac output, vascular peripheral resistance, and blood volume, but can be altered by a tiered network of numerous neural, hormonal and cellular mechanisms that directly or indirectly modulate any one of the three primary determinants.  The expansive network, e.g., numerous organs and tissues, and multiple and intersecting effects of different mechanisms within the network, e.g., the renin-angiotensin-aldosterone system modulates both vascular resistance and blood volume) make it difficult to see the network in its entirety.  Nevertheless, students must understand and master the entire network, the individual mechanisms, and the nuances.  Thus, in preparing for the cardiovascular section and planning how to implement the concept map, I made a list of all components that comprised the regulatory network for blood pressure with the first terms being blood pressure, cardiac output, vascular peripheral resistance, and blood volume.  At this point in the semester, the students had learned the basics of cellular respiration and metabolism.  I began the very first cardiovascular lecture with an illustration of the human circulatory system projected on the screen as I worked at the white board.  In the center of the board, I drew a cell with a single mitochondrion and three simple arrows to indicate the use of glucose and oxygen to convert ADP to ATP.  Guided through a series of questions and answers, students collectively explained that the heart must pump blood through arteries and veins to deliver oxygen and glucose and fat needed to generate ATP, as well as to remove carbon dioxide and other wastes.  Using the illustration of the human circulatory system, I then carefully explained the human circulatory system is a closed system comprised of the blood (the medium carrying oxygen, nutrients, CO₂ and other wastes), the heart (the pump), and the arterial and venous vessels (the conduits in which blood flows from the heart to the tissues where oxygen and nutrients are delivered and CO₂ and other wastes are removed).  If adequate pressure is sustained, blood continues to flow through veins back through the heart and to the lungs to unload CO₂ and reoxygenate blood and then back to the heart to make another round.  I further explained blood pressure must be regulated to ensure blood flow to tissues optimally matches both metabolic need for oxygen and nutrients and production of CO₂.  On the board, I then wrote “Blood Pressure (BP)” and stated that because this is a closed circulatory system, blood pressure changes in direct response and proportion to cardiac output or volume of blood pumped out of heart into systemic vessels in one minute, the total volume of blood in the system, and the vascular resistance that opposes flow and will be predominantly dependent vasoconstriction and vasodilation.  I wrote the terms “Cardiac Output (CO), Blood Volume (BV), and Vascular or Total Peripheral Resistance (VPR) one at a time underneath BP, each with an arrow pointing directly to BP.  I stated that any factor that changes cardiac output, blood volume, or vascular resistance can indirectly alter blood pressure.  For example, a change in heart rate can change cardiac output and thus, alter blood pressure.  I then distributed the series of hand drawn diagrams shown below.  As I pass out the sheets and display on slides, I tell them they will be learning about all these various factors and mechanisms and will be able to recreate the network and use it as a study aid.

To get students started, I handed out the list of cardiovascular terms, hormones, equations, etc. and several small pieces of paper, e.g., 2”x2” plain paper squares, to each student.  [I found free clean scratch paper in various colors in the computer lab and copy room recycling bins.]  Students can also take their trusty 3”x5” cards and cut each in half or even quarters or use standard-size Post-It® notes.  I explained that as I introduce a term or mechanism they will write the term or conventional abbreviation on one side of the paper and the definition and pertinent information on the other in pencil for easier editing.  [I emphasized the importance of using conventional abbreviations.]  For example, Blood Pressure would be written on one side of the paper and ‘pressure exerted against vessel wall’ on other, along with ‘mm Hg’, and later the equation for mean arterial pressure (MAP) can be added.  I had my own set of terms written on Post-It® notes and arranged BP, CO, BV, VPR and other terms on a white board so they could see the mapping of functional relationships take shape.  As new concepts were taught and learned, e.g., CO = Stroke Volume (SV) x Heart Rate (HR), the respective terms were added to the concept map to reflect the physiological relationships between and among the new mechanism to the existing mechanisms or phenomena already in the concept map.  In that case, on the back of the CO paper or card one might write “volume of blood ejected from ventricle in one minute into aorta”, “CO = HR x SV“, “If HR is too fast, CO will decrease!”, “Right CO must equal Left CO!”  I explained students can lay out their terms on a table, floor, their bed, etc.  I reminded students how important it was to say the terms out loud as they wrote the terms in their best penmanship.  This helps students slow down and deliberately think about what they are writing and refer to their lecture notes or textbook (be it an actual book or e-book).  I had given students copies of the complete concept map of all terms but did not dictate exactly what they should write on the back of the cards.  The small size of the paper or card, almost forces students to annotate explanations; this helped them better encapsulate their ideas.  I was open to checking their annotation and reflecting back to students the apparent meaning of their word choice.  While studying alone or with study partners, students were encouraged to audibly define terms and relationships among mechanisms as they arranged their maps in the correct configuration.  They were encouraged to ‘shuffle the deck’ and recreate subsections of the network to understand mechanistic connections at different points in the network.  Because I had given them the diagrams or concept maps for cardiac output, blood volume, and vascular resistance, students were able to check their work and conduct formative assessments alone or in groups in an accurate and supportive manner.

Students expressed that manually arranging components allowed them to literally see functional and consequential relationships among different mechanisms.  The activity complemented and re-enforced quizzes and formative assessments already in use.  It’s not a perfect tool and certainly has room for improvement.  There are quite a few pieces of paper, but students found ways to keep the pieces together, e.g., binder clips, Zip-lock bags, rubber bands.  Nonetheless, it is simple, portable, and expandable concept map students can use to learn cardiovascular physiology and represents a tool that can be applied to teach and learn other regulatory networks, such as those of the digestion-reabsorption-secretion in the GI tract and calcium homeostasis.

1. Wiggers C. Circulation in Health and Disease. Philadelphia, PA: Lea & Febiger, 1915.
2. http://learnthroughexperience.org/blog/power-of-context-learning-through-senses/

Alice Villalobos, Ph.D., is an assistant professor in the Department of Medical Education at the Texas Tech Health Sciences Center in Lubbock, Texas.  She received her B.S.in biology from Loyola Marymount University and her Ph.D. in comparative physiology from the University of Arizona-College of Medicine.  Her research interests are the comparative aspects of the physiology and stress biology of organic solute transport by choroid plexus.  She has taught undergraduate and graduate courses in integrative systems physiology, nutrition and toxicology.  However, her most enjoyable teaching experience has been teaching first-graders about the heart and lungs!  Her educational interests focus on tools to enhance learning of challenging concepts in physiology for students at all levels.  She has been actively involved in social and educational programs to recruit and retain first-generation college students and underrepresented minorities in STEM.