How to Revise Physiology for MRCEM Primary: A Subdomain-by-Subdomain Plan

Facts last verified 30 May 2026.

TL;DR. Physiology is 60 of the 180 questions on the MRCEM Primary — exactly 33.3% of the paper, tied with anatomy as the largest single domain. The six examined subdomains are basic cellular, respiratory, cardiovascular, gastrointestinal, renal and endocrine physiology. If you are finding it the hardest of the five basic-science domains, three things help more than anything else: (1) work directly from the RCEM Basic Sciences Curriculum subdomain by subdomain rather than a generic textbook, (2) do timed SBAs from week one and revise the explanations not the score, and (3) front-load cardiovascular and respiratory physiology — they generate the highest yield of marks because RCEM loves to integrate them with anatomy, pharmacology and ED presentations. See also our guide to how anatomy and physiology are weighted in MRCEM Primary.

flowchart LR
    W1[Week 1
Cardiovascular] --> W2[Week 2
Respiratory]
    W2 --> W3[Week 3
Renal, acid-base]
    W3 --> W4[Week 4
Neurophysiology]
    W4 --> W5[Week 5
Endocrine, GI]
    W5 --> W6[Week 6
Haematology, immunology]
    W6 --> W7[Week 7
Mixed SBA practice]
    W7 --> W8[Week 8
Weak spots + mock]

If you are six to ten weeks out, anatomy is fine but physiology feels bottomless, you are not alone. Across r/doctorsUK and the IMG groups the same line keeps coming back: “physiology is the bit that decides whether I pass or fail.” The good news — it is the most learnable of the basic-science domains. There is a finite curriculum, a predictable question style, and a small set of concepts that get asked over and over. This guide is how to revise it properly, in the time you actually have.

How much physiology is actually on the MRCEM Primary?

Per the MRCEM Primary Regulations & Information Pack (November 2023), the 180-question paper splits as follows:

Anatomy and physiology together carry two-thirds of every mark. If you treat physiology as a small section you can hand-wave in the last fortnight, you will fail. The candidates we see passing first time spend roughly a third of their total revision hours on physiology — the same as anatomy — and that ratio is non-negotiable.

What physiology subdomains does RCEM examine?

The official blueprint lists six subdomains under physiology. RCEM does not publish an exact per-subdomain question count, but candidate feedback from the last several sittings — and the depth of the curriculum entries themselves — gives a reliable priority ranking. Use this table to allocate hours, not as a rigid quota. See also our guide to building an Anki deck for MRCEM Primary.

Two things drop out of this immediately. First, cardiovascular and respiratory together are about half the physiology paper — front-load them. Second, renal is the subdomain that catches most candidates out, so build in dedicated time for it rather than hoping it sticks on a second pass.

Why does physiology feel harder than the other basic sciences?

Three reasons, all fixable.

• It is conceptual, not factual. Anatomy and pharmacology reward rote learning — the brachial plexus does not change, neither does the dose of adrenaline. Physiology requires you to reason from first principles about a graph, a feedback loop or a pressure change. If you try to memorise it as facts, the question stems will defeat you.
• The questions are integrated. RCEM rarely asks “what is GFR?” They ask “a 70 kg man bleeds 1.5 L — which of the following best describes the renal response in the next 30 minutes?” You need the physiology and the clinical context together.
• Most candidates over-rely on a single textbook. One textbook gives you one author’s framing. Physiology clicks when you see the same loop drawn three different ways — which is why video plus textbook plus questions beats textbook alone every time.

How should I structure my physiology revision week by week?

A 12-week run-up is what most successful candidates report. If you have less time, compress proportionally — but do not skip the question-bank weeks, they are where the marks come from.

• Weeks 1–2 — Cardiovascular. Cardiac cycle and ECG genesis, pressure-volume loops, preload/afterload/contractility, Starling curve, baroreceptor and chemoreceptor reflexes, shock physiology. Pair every concept with a clinical scenario (cardiogenic shock, tamponade, sepsis).
• Weeks 3–4 — Respiratory. Lung volumes and capacities, compliance, work of breathing, oxygen-haemoglobin dissociation curve and its shifts, CO2 transport, V/Q ratios and dead space, control of ventilation, response to altitude and exercise.
• Weeks 5–6 — Renal & acid-base. GFR and its determinants, tubular handling segment by segment, counter-current multiplier, RAAS, ADH, the four primary acid-base disorders with full compensation rules. Drill ABG interpretation questions daily this fortnight.
• Week 7 — Endocrine. HPA axis, thyroid hormone synthesis and effects, insulin/glucagon and the fed-fasted switch, calcium homeostasis (PTH, vitamin D, calcitonin), posterior pituitary.
• Week 8 — Basic cellular & neurophysiology. Resting and action potentials, synaptic transmission, neuromuscular junction, skeletal vs smooth vs cardiac muscle, reflex arcs, autonomic outflow, basics of cerebral perfusion and ICP.
• Week 9 — Gastrointestinal. Salivary, gastric, pancreatic and biliary secretion; absorption of carbohydrate, protein, fat, iron and B12; hepatic metabolism and bilirubin handling.
• Weeks 10–12 — Integration and timed SBAs. Mixed-domain papers under exam conditions. Review every wrong answer back to its curriculum entry. Stop adding new material in week 12 — consolidate.

Which resources actually work for MRCEM Primary physiology?

You do not need a long list. You need one textbook for reference, one source of moving images, and one question bank. Anything more is procrastination.

• Core textbook: Physiology at a Glance (Ward, Linden & Clarke). Mapped almost perfectly to the depth RCEM wants. Each topic is two pages — left page diagram, right page prose. Read it cover to cover; you will get through it in a week of evenings.
• Curriculum-mapped reference: Revision Notes for the MRCEM Primary (Mark Harrison, latest edition). Dry, but it is the only book written explicitly to the RCEM blueprint. Use it to look up topics the question bank flags as weak.
• Video: Armando Hasudungan and Strong Medicine on YouTube. Free, channel-quality drawn explanations for cardiovascular, respiratory and renal. For neuroanatomy and neurophysiology, Acland’s Video Atlas of Human Anatomy (free at many NHS libraries) is the visual reference most candidates wish they had used sooner — particularly for brainstem, cranial nerves and the autonomic outflow questions that RCEM bundle into the physiology slot.
• Question bank: MRCEMSuccess or Pastest MRCEM Primary. Pick one and finish it. Both have ~3,000 SBAs. The explanations are where the learning happens — read every one, not just the wrong answers.
• Spaced repetition: Anki. Build a small physiology deck (200–400 cards) of the formulas, graphs and reflex loops you keep getting wrong. Our Anki strategy piece covers the deck choice and review settings.
• RCEM Basic Sciences Curriculum (June 2010 PDF). Free from rcem.ac.uk. Print it. Tick off subdomain entries as you cover them. It is your road map and your stop signal — when an entry is ticked off and your SBA accuracy on it is >75%, move on.

What is the most efficient way to use a physiology question bank?

Start questions in week one, not week eight. The standard mistake is to read for two months and only then attempt SBAs — by which point you have wasted half your study time learning at the wrong depth. See also our guide to Acland’s anatomy videos for MRCEM Primary.

• Daily blocks of 20 questions in the subdomain you are currently studying. Untimed for the first week of any new subdomain, timed thereafter.
• Read every explanation — right or wrong. The explanation tells you the depth RCEM expects. If the explanation references something you did not know, add it to Anki.
• Tag wrong answers by subdomain and re-attempt them the following week. Anything wrong twice goes on a “red list” for week 11 review.
• Full timed mocks from week 9. Sit four to six 180-question papers under exam conditions. Your accuracy on these — not your reading speed — predicts your result.

How deep should I go on each physiology topic?

This is the single most common reason candidates run out of time. The RCEM curriculum is explicit about depth — it will say “understands the mechanism of” or “can describe the” rather than “can derive from first principles”. If the curriculum says describe, do not learn the molecular biology; if it says understand the mechanism, you need the loop and the trigger, not the gene.

Practical heuristic: if you cannot find it asked in a question bank after four weeks of revision, you are probably going too deep. Three rules of thumb that hold across every sitting:

• You need the graph, the axes and the shift. Oxygen-haemoglobin curve, Starling curve, pressure-volume loop, GFR autoregulation — draw them from memory and label every shift. Almost every cardiovascular and respiratory question can be solved from one of these.
• You need the feedback loop, not the histology. RAAS, baroreceptor reflex, HPA axis, calcium homeostasis — know the stimulus, the sensor, the effector, the response, and what blocks each step.
• You need the numbers RCEM cares about. Normal GFR (~125 mL/min), normal cardiac output (~5 L/min), normal MAP (~93 mmHg), pH 7.35–7.45, PaO2 >10.6 kPa. A short numbers sheet is worth more than a chapter of prose.

How do I handle the renal physiology questions?

Renal is the subdomain candidates most often flag as the hardest, and the questions tend to cluster around three things: tubular handling, acid-base, and RAAS/ADH regulation. Treat it as its own mini-curriculum.

• Draw the nephron from glomerulus to collecting duct. Label what is reabsorbed and secreted at each segment, and which drug class acts where (this gives you free pharmacology marks too).
• Learn the four primary acid-base disorders and their compensation formulas. Drill 20 ABG questions until you can identify, classify and quantify compensation in under 60 seconds each.
• Build a one-page RAAS diagram with every step (renin → angiotensinogen → AT-I → ACE → AT-II → aldosterone) and the stimuli that switch it on. RCEM repeat-tests this every sitting.

How do I make cardiovascular physiology stick?

Cardiovascular physiology is the highest-yield subdomain — and it is also the one most amenable to learning by graph. Three diagrams underpin almost every question:

• The Wiggers diagram. Time on the x-axis, pressures and volumes on the y. From this single picture you can answer questions about valve timing, heart sounds, ejection fraction, and the effect of arrhythmia.
• The pressure-volume loop. Know what preload, afterload and contractility do to each corner. Layer on the loops for aortic stenosis, mitral regurgitation and heart failure.
• The Frank-Starling curve plus the venous return curve. The intersection point is cardiac output. Shift either line and you can predict the effect of fluid, vasopressors, sepsis or tamponade.

What about respiratory physiology — what gets tested most?

Respiratory is the second-highest-yield subdomain. The recurring themes are:

• The oxygen-haemoglobin dissociation curve. Know every factor that shifts it left or right, the P50, and the clinical consequence (e.g. why a septic patient unloads more O2 at the tissues).
• Lung volumes and capacities. Be able to draw and label the spirometry trace including residual volume. Know which volumes change in obstructive vs restrictive disease.
• V/Q matching and dead space. Understand the apex-to-base gradient in the upright lung and what changes in PE, pneumonia, ARDS.
• Control of ventilation. Peripheral vs central chemoreceptors, response to hypoxia, hypercapnia and acidaemia.

How do I avoid the most common physiology revision mistakes?

The Reddit and IMG group post-mortems from failed sittings keep flagging the same five errors. Avoid them and you give yourself a real chance.

• Treating physiology as a memory test. If you are writing flashcards for every fact, you are revising at the wrong level. Cards should be for graphs, formulas and the handful of numbers RCEM care about.
• Saving question practice for the last month. By that point your reading depth is already wrong, and you cannot recalibrate. Start questions in week one.
• Ignoring acid-base because it feels separate. It is examined under renal but also embedded in respiratory and even endocrine (DKA) stems. Drill it for at least one full week.
• Skipping endocrine and GI because they are small. They are small but they are scorable — typically 8–15 marks combined. Three days of focused work gets you most of those marks.
• Not revisiting wrong answers. A wrong SBA you do not re-attempt is just a wrong SBA. The candidates who pass build a red list and clear it twice before the exam.

Frequently asked questions

Is physiology really worth a third of my revision time?

Yes. It is 60 of 180 questions — exactly 33.3% of the paper. Allocating less than a third of your hours to it is mathematically betting against yourself.

Which physiology subdomain is the hardest?

Renal — by candidate report and by the integrative nature of the questions (nephron handling plus RAAS plus acid-base in a single stem). Give it a dedicated fortnight rather than tacking it onto cardiovascular.

Do I need a paid revision course just for physiology?

No. A good textbook (Physiology at a Glance) plus free YouTube channels (Armando, Strong Medicine) plus a question bank covers everything. Paid courses help with motivation and timing practice but are not required for physiology specifically.

How many physiology SBAs should I do before the exam?

Aim to attempt every physiology question in one major bank (typically 700–1,000 questions) at least once, and your tagged-wrong subset at least twice. That gets most candidates to a consistent 75%+ on physiology mocks.

Do I need to know cellular and molecular detail?

Only at the depth the curriculum specifies. RCEM expect you to understand mechanisms — receptors, second messengers, ion channels at action-potential level — but not gene expression or signalling pathways in molecular biology detail. If a textbook is going deeper than your question bank tests, stop and move on.

Should I revise physiology alongside anatomy or in blocks?

Block by subdomain works better for most candidates — your brain holds a physiology system more reliably when it is the only thing you are studying that week. Pair them only in the last fortnight of mixed timed papers, which is when integration matters most.

How important are the graphs?

Critical. If you can draw the Wiggers diagram, pressure-volume loop, oxygen-haemoglobin curve, Frank-Starling curve and nephron from memory and label every shift, you have answered a large proportion of the physiology paper before walking in.

Is neurophysiology a separate subdomain?

Not in the blueprint — it sits under basic cellular physiology (action potentials, synaptic transmission, neuromuscular junction) and overlaps the anatomy paper for cranial nerves and reflex arcs. Cover it in the basic cellular week and rely on your anatomy revision for the rest.

Is there negative marking on the MRCEM Primary?

No. Answer every question — a guess is free expected value. The pass mark is set using the Angoff method, not a fixed percentage.

How early should I do my first timed mock?

By week 9 of a 12-week plan. Sit four to six full 180-question papers under exam conditions in the final three weeks. Mocks earlier than that are diagnostic rather than predictive.

Your next step

Physiology is the most learnable of the basic sciences once you stop treating it like a memory test and start treating it like a small number of graphs, loops and numbers tested in clinical contexts. Print the curriculum, block out your weeks by subdomain, start the question bank in week one, and front-load cardiovascular and respiratory. Do that and the 60 marks on offer are very much yours to take.

For exam-mapped SBAs, walkthrough explanations and a structured 12-week MRCEM Primary plan covering anatomy, physiology, pharmacology, microbiology, pathology and EBM, head to emfinalexams.com.

Ready to build your plan? EMF Premium gives you all 40,000+ questions, 20 mocks and 1,215 OSCE stations from £29/month — or a one-off 3- or 6-month pass.