How to study physiology: follow the mechanism, then test yourself on it

The short answer

Study physiology as chains of cause and effect, not lists of facts. For each topic, ask what changes, what senses it, what responds and what that does next, and draw it: a flow diagram of the chain, and the key graphs, such as the pressure–volume loop, the Frank–Starling curve and the oxygen–haemoglobin dissociation curve, until you can redraw and explain them from memory. Then test that understanding: predict what happens when one variable changes, work through problems, and explain it out loud without notes.

Do it again and again, spread out: come back to each mechanism the next day and at growing gaps, and link it to the anatomy underneath and the diseases that break it. Physiology teachers name causal reasoning, graphs and how much the subject ties together as what makes it hard, and students treating learning as memorising as a main obstacle (Michael, 2007); in one anatomy and physiology course, short recall quizzes spread over the semester left students remembering 41% more than a control group (Dobson, 2013).

Why physiology is hard

Physiology is less about facts than about how things cause each other: a pressure changes, a receptor notices, a reflex responds, and the response changes something else. When Joel Michael (2007) asked 63 physiology teachers what makes it hard to learn, they pointed to the subject itself, which needs causal reasoning, uses graphs and maths and ties everything together, and to students, who often believe learning and memorising are the same thing and keep each topic in its own compartment.

The way out is that a few ideas explain most of it. Harold Modell (2000) proposed seven general models that recur throughout the body: control systems, conservation of mass, mass and heat flow, the elastic properties of tissues, transport across membranes, cell-to-cell communication and molecular interaction. The Fick equation for cardiac output and a renal clearance look like two different things to learn, but both are conservation of mass. Learn the models once, and each new topic becomes another case of them.

The method, a step at a time

Every topic, from the cardiac cycle to acid–base balance, can be studied the same way: find the chain of cause and effect, draw it, and check that you can run it forwards and backwards from memory.

1. Make sure of the ground first: the anatomy of the organ and the few physical rules it runs on, such as flow depending on the pressure difference and the resistance, or diffusion depending on the gradient and the surface area.
2. Read for the chain. For each topic, write down what changes, what senses it, what responds and what the response does. For the baroreceptor reflex: blood pressure falls, the receptors in the carotid sinus and aortic arch are stretched less and fire less, the brainstem raises sympathetic and lowers vagal output, heart rate, contractility and vessel tone rise, and the pressure comes back up.
3. Close the book and draw the chain as a flow diagram, with arrows marked up or down. Then open it and correct what you missed.
4. Ask what if. Change one thing, such as a haemorrhage, standing up suddenly or going to altitude, and predict what follows, step by step, before you check.
5. Work problems with numbers wherever the topic has them: cardiac output, clearance, the alveolar gas equation, acid–base cases. Being able to calculate it is a test of understanding it.
6. Explain it out loud without notes, as you would at an oral. The places where you hesitate are your next review.
7. Link it: to the anatomy underneath, to the topics it depends on, and later to the diseases and drugs that change it.

Draw the graphs until you can explain every line

Graphs are where physiology exams find out whether you understand. Learn a few of them well enough to draw them on a blank page, label the axes, and say what each part means and what moves it.

The pressure–volume loop of the left ventricle: its four phases, filling, isovolumetric contraction, ejection and isovolumetric relaxation, and what happens to the loop when preload, afterload or contractility changes. The Frank–Starling curve: stroke volume rising with end-diastolic volume, the curve moving up with more contractility and down in heart failure. The oxygen–haemoglobin dissociation curve: its S shape, why it’s flat at the top and steep in the middle, and what shifts it to the right: more carbon dioxide, more acid, a higher temperature and more 2,3-BPG.

Draw each one from memory first, then check it. Then draw two states on the same axes, such as rest and exercise, or a healthy heart and a failing one, and explain the difference out loud.

Concept maps, and explaining it to yourself

Concept maps, where each idea is a box and each arrow says how one affects another, suit physiology because it’s a web of causes. In a randomised study in a medical physiology course by González and colleagues (2008), students who built concept maps of the cardiovascular module and used them to solve problems did better on problem-solving exams than a control group, though not on multiple-choice ones.

How you make the map matters. Jeffrey Karpicke and Janell Blunt (2011) found that practising recall produced more learning than building concept maps with the text in front of you, even on questions that needed inference; in a later study, Blunt and Karpicke (2014) found that maps built from memory worked as recall practice too. So draw the map with the book shut, then open it and fix it.

Explaining works the same way. In a study by Michelene Chi and colleagues (1994), students asked to explain to themselves each line of a text on the human circulatory system learned more than students who read it twice, and those who explained the most all arrived at a correct model of how the circulation works. Explain each step of a mechanism, to yourself or out loud to a classmate, and say why, not just what.

In Breef, each mechanism can be a note of its own, linked with [[double brackets]] to the ones it depends on: a note on the renin–angiotensin system links to the kidney, to blood pressure and to aldosterone, and Knowledge draws them all as one map, so you can see where a topic connects and where it doesn’t yet.

Spaced review, and links to anatomy and pathology

Understanding a mechanism once doesn’t mean you’ll still have it at the exam. In Dobson’s study (2013) of an anatomy and physiology course, ten short recall quizzes spread over the semester, two hours in all, left students remembering 41% more of the material at the end than a control group, whether the gaps between quizzes grew or stayed the same. Come back to each mechanism the day after you study it, again a few days later, then about a week later and every week or two after that: Cepeda and colleagues (2008) found the best gap grows with how long you need to remember, from about 20 to 40% of the time to the test when that was a week to about 5 to 10% when it was a year.

Each review is a chance to link. Physiology sits between anatomy, which shows where things happen, and pathology and pharmacology, which show what happens when they go wrong. The loop of Henle makes more sense once you’ve drawn the nephron; heart failure is easier to follow on the Frank–Starling curve you already know. Those links are why physiology is worth learning well: it comes back in almost every clinical subject.

Breef can take care of the scheduling. Record a lecture in a note and Breef writes it up, with what the lecturer stressed; the note comes back for review the next day and then at gaps fitted to how fast you forget, with three questions written from it each time; and an exam date gets every note that would fade by then a last review in the days before.

A plan for the weeks before the exam

Physiology exams test whether you can reason with what you know, so the last weeks are for practising exactly that.

1. Six weeks out: list the topics on the syllabus and mark each by whether you can draw and explain it from memory, partly, or not yet. Start with the general ideas, membranes, transport and control systems, since the rest is built on them.
2. Weeks six to three: one system at a time, with the method above, starting each day by recalling the mechanisms and graphs from the days before.
3. Week two: problems and cases. Work through past exam questions and what-if cases that cross systems, such as exercise, haemorrhage or altitude, where the heart, lungs and kidneys respond together.
4. The last week: only recall. Draw every key graph and flow diagram from memory, explain each out loud, and look things up only to fix what you got wrong.
5. The day before: go over the mechanisms you were shakiest on, and get a full night’s sleep.

Common mistakes

Memorising the steps of a mechanism as a list. If you can’t say why each step follows from the one before, a question that starts from a different point will catch you out.

Learning the graphs as pictures. Draw them, label them, and explain what moves them.

Making beautiful concept maps with the book open. Build them from memory, then check.

Keeping each system in its own box. The body doesn’t: exercise, shock and altitude involve several systems at once, and exams like those questions.

Skipping the numbers. Calculations show whether you understand a relationship, and they’re often the easiest marks.

Studying in silence before an oral. Explain it out loud, to a classmate or to yourself, before an examiner asks you to.