Tag Archives: physiology in the classroom

It was Just a Bag of Candy, but Now It’s a Lung – Don’t Be Afraid to Improvise When Teaching Physiology

Many of us have been teaching the same course or the same topic in a team-taught course for many years.  I have been teaching the undergraduate Anatomy and Physiology-II (AP-II) course at a community college for four years.  People often ask, “Doesn’t it get old?  Don’t you get bored, teaching the same topic?”  Without hesitation, I answer, “No.” Why?  First, on-going research continually brings new details and insight to nearly every aspect of cell and integrative physiology.  You’re always learning to keep up with the field and modifying lectures to incorporate new concepts.  Second, you truly want your students to learn and enjoy learning and continually seek out ways to teach more effectively.  You try new approaches to improve student learning.  However, the third reason is truly why teaching physiology will never get old or dull.  No two students and no two classes are alike; individual and collective personalities, career goals, academic backgrounds and preparedness, and learning curves vary from class to class.  About half my students have not taken the general biology or chemistry courses typically required for AP-I or AP-II (these are not required by the college).  The unique combination of characteristics in each group of students means that on any given day I will need to create a new makeshift model or a new analogy for a physiological mechanism or structure-function relationship to help students learn.  Thus, even if all physiological research came to complete fruition, the teaching of physiology would still be challenging, interesting, and entertaining.  Many of my peers share this perspective on teaching physiology.

Irrespective of one’s mastery of integrative physiology, as teachers we must be ready and willing to think creatively on our feet to answer questions or clarify points of confusion.  A common mistake in teaching is to interpret the lack of questions to mean our students have mastered the concept we just explained, such as the oxygen-hemoglobin dissociation curve.  Despite the amazing color-coding of green for pH 7.35, red for pH 7.0 and blue for pH 7.5 and perfectly spaced lines drawn on that PowerPoint slide, your Ms./Mr. Congeniality level of enthusiasm, and sincerest intentions – you lost them at “The relationship of oxygen saturation of hemoglobin to the partial pressure of oxygen is curvilinear.”  You know you lost them.  You can see it in their faces.  The facial expression varies: a forehead so furrowed the left and right eyebrows nearly touch, the cringing-in-pain look, the blank almost flat stare, or my favorite – the bug-eyed look of shock.  Unfortunately, it will not always be obvious.  Thus, it is essential we make an effort to become familiar with the class as a group and as individuals, no matter how large the class.  Being familiar with their baseline demeanor and sense of humor is a good start.  (I have students complete ‘Tell Me About Yourself’ cards on the first day of class; these help me a great deal.)  During lecture, we make continual and deliberate eye contact with the students and read their faces as we lecture and talk to them, rather than at them.  In lab we work with and talk to each group of students and even eavesdrop as a means to assess learning.  Time in class or lab is limited, which tempts us to overlook looks of confusion and move on to the next point.  However, when students do not accurately and confidently understand a fundamental concept, they may have even greater difficulty understanding more integrated and complicated mechanisms.  You must recognize non-verbal, as well as subtle verbal cues that students are not following your logic or explanation.  In that immediate moment you must develop and deliver an alternative explanation.  Improvise.

As per Merriam-Webster, to improvise is to compose, recite, play, or sing extemporaneously; to make, invent, or arrange offhand; to fabricate out of what is conveniently on hand.  What do you have on hand right now to create or develop a new explanation or analogy?  Work with what you have within the confines of the classroom.  These resources can be items within arm’s reach, anything you can see or refer to in the classroom.  You can also use stories or anecdotes from your own life.  Reference a TV commercial, TV show, movie, song, or cartoon character that is familiar to both you and your students.  Food, sports, and monetary issues can be great sources for ideas.  I cook and sew, which gives me additional ideas and skills.  Play to your strengths.  Some people are the MacGyvers of teaching; improvisation seems to be a natural born gift.  However, we all have the basic ability to improvise.  You know your topic; you are the expert in the room.  Tap into your creativity and imagination; let your students see your goofy side.  Also, as you improvise and implement familiar, everyday things to model or explain physiological or structure-function relationships you teach your students to think outside the box.  Students learn by example.  My own undergraduate and graduate professors improvised frequently.  My PhD and post-doc advisors were comparative physiologists – true masters of improvised instrumentation.

Improvise now, and improve later.  Some of my improvised explanations and demonstrations have worked; some have fallen flat.  In some cases I have taken the initial improvised teaching tool and improved the prototype and now regularly use the demonstration to teach that physiological concept.  Here are three examples of improvisational analogies I have used for the anatomy of circular folds in the intestine, the opening and closing of valves in the heart, and the role of alveoli in pulmonary gas exchange.  Disclaimer:  These are not perfect analogies and I welcome comments.

Surface area in the small intestine.  Students understand that the surface area of a large flat lab table is greater than the surface area of a flat sheet of notebook paper.  A sheet of paper can be rolled into a tube, and students understand that the surface area of the ‘lumen’ is equal to the surface area of the paper.  In AP-I, students learned that microvilli increase the surface area of the plasma membrane at the apical pole of an epithelial cell, and many teachers use the ‘shag carpet’ analogy for microvilli.  Similarly, they understood how villi increase surface area of the intestinal lumen.  However, some students did not quite understand or cannot envision the structure of circular folds.  As luck would have it, I was wearing that style of knit shirt with extra-long sleeves that extend just to your fingertips.  I fully extended the sleeve and began to explain. “My sleeve is the small intestine – a tube with a flat-surface lumen (my arm is in the lumen) – no circular folds.  This tube is 28 inches long and about 8 inches around.  As I push up my sleeves as far as I can, and the fabric bunches up.  These messy folds that form are like circular folds.  And, now this 6 inch tube with all these circular folds has the same surface area as the 28-inch plain tube.”  (I sew; I know the length of my own arm and am great at eyeballing measurements.)

Heart valves open and close as dictated by the pressure difference across the valve.  This is integral to ventricular filling, ejection of blood into the lung and aorta, and the effect of afterload.  Heart valves are one-way valves.  A few students heard ‘pressure difference’ and were lost.  Other students had trouble understanding how stroke volume would decrease with an increase in afterload.  What can I use in the room?  There’s a big door to the lab, and it has a window.  It opens in one direction – out, because of the doorframe, hinges and door closure mechanism; it only opens, if you push hard enough.  I ran over to the door.  “The lab door is a heart valve.  It’s the mitral valve, the lab is the atrium, and the hallway is the ventricle.  The door only opens into the hall – the mitral valve only opens into the ventricle.  When it closes, it stops once it sits in the frame.”  I asked a student about my size to go outside the room, and push against the door closed – but let me open it; she could see and hear me through the window.  “As long as I push with greater force than she applies to keep it shut, the door or valve will open.”  The student played along and made it challenging, but let me open the door.  ‘Blood flows from the atrium into the ventricle, as long as the valve is open.  But, as soon as the pressure in the ventricle is greater than the pressure in the atrium the valve closes.”  The student forcefully pushed the door shut.  They got it!  Now, afterload …?  Back to the lab door.  “Now the lab door is the aortic valve, the lab is the left ventricle, and the hall is the aorta.  This valve will open and stay open as long as the pressure in the ventricle is greater than the pressure in the aorta.  The longer the valve is open, the greater the volume of blood ejected from the ventricle.  The volume of blood ejected from the ventricle in one beat is the stroke volume.  The pressure that opposes the opening of the aortic valve is afterload.  What happens with afterload?”  I then asked the tallest, strongest student in class to play the role of Afterload; he too got into the role.  “Afterload has now increased!  The pressure that opposes the opening of the valve has increased.  Will I or won’t I have to push harder to open the door – now that afterload has increased?”  The student is very strong; I can barely push the door open.  “I not only have to push harder, but I can’t keep the door or valve open for very long.  Look.  Even though the ventricle pressure is greater, the valve is open for a shorter period – so less blood is ejected and stroke volume decreases.”

Alveoli increase the surface area for gas exchange.  Students see the lungs as 2 large sacs, and the surface area available for gas exchange between air and blood is simply the inner lining of each sac.  However, each lung is made of millions of tiny air sacs or alveoli into which air flows.  How this anatomical arrangement greatly increases surface area for gas exchange is not intuitively obvious.  The overall size of the lung does not increase, so why would the surface area increase?  As luck would have it, it was Halloween.  I had brought a big bonus bag of individually wrapped bite-size candies to class.  “One lung is like this bag.  If we cut open the bag and measure the sheet of plastic, it would be about 18 inches by 12 inches or 216 square inches.  But if we completely fill it with candy, it might hold at least 150 pieces of candy.”  I quickly unwrapped one piece of candy, held up the wrapper, and estimated a single wrapper was 4 square inches.  “If we fill one bag with 150 pieces of candy, we then have 600 square inches of surface area.  Which would provide greater area for gas exchange: one big lung or millions of alveoli?”  I revised this particular improvised explanation using scissors, a ruler and two 11-oz bags of Hershey’s® kisses.  I carefully opened both bags and transferred kisses from one bag to the other, until it was completely full, i.e., 112 kisses, and taped it shut.  I then fully opened up the other bag; it was 10 inches x 8 inches or 80 square inches.  An individual kiss wrapper is 4 square inches; all 112 individual wrappers are 448 square inches.

My improvised analogies are not perfect, but they have served as great teaching tools.  If you can improve upon these, please do.  Share any suggestions you have and lastly, share your improvised explanations and analogies.  Thanks.

Alice Villalobos received her B.S.in biology from Loyola Marymount University and her PhD in comparative physiology from the University of Arizona-College of Medicine.  She has been in the Department of Biology at Blinn College for 4 years where she teaches Anatomy and Physiology II and Introduction to Human Nutrition.  She guest lectures in undergraduate courses at Texas A&M University on the topics of brain barrier physiology and the toxicity of heavy metals.