MRCP Physiology: Cardiovascular Reflexes

TL;DR:

Cardiovascular reflexes are a compact, high-yield physiology topic that repeatedly appears in MRCP Part 1 questions. Examiners test your ability to link a trigger (e.g. posture, hypovolaemia, raised ICP) to predictable heart rate and blood pressure responses. Understanding mechanisms—not rote facts—wins marks quickly.

Why this matters

Cardiovascular reflexes are a favourite for MRCP examiners because they are clinically intuitive yet frequently misunderstood. A short stem describing standing up, blood loss, myocardial infarction, or raised intracranial pressure can test your grasp of autonomic physiology within seconds.

For MRCP Part 1 candidates, the challenge is not the number of reflexes but confusing which reflex dominates in which situation. This article distils the scope, highlights the most tested reflexes, and shows how to approach questions systematically. For overall exam structure and topic weighting, refer to the official MRCP(UK) Part 1 examination page.

Scope of cardiovascular reflexes in MRCP Part 1

You are expected to understand cardiovascular reflexes at a functional, applied level, not as isolated anatomy. Most questions assess:

• The stimulus (pressure, stretch, hypoxia, ischaemia)

• The receptors involved

• The autonomic response (sympathetic vs parasympathetic)

• The net haemodynamic effect

Complex neuroanatomical pathways are rarely required. Instead, MRCP Part 1 rewards pattern recognition and physiological reasoning.

High-yield cardiovascular reflexes (exam outline)

1) Arterial baroreceptor reflex

• Receptors: Carotid sinus, aortic arch

• Stimulus: Change in arterial blood pressure

• Response: Rapid adjustment of heart rate, contractility, and vascular tone

• Exam focus: Primary short-term regulator of blood pressure

2) Bainbridge reflex

• Receptors: Right atrial stretch receptors

• Stimulus: Increased venous return

• Response: Increased heart rate due to reduced vagal tone

• Exam focus: Seen with acute fluid loading, less important chronically

3) Bezold–Jarisch reflex

• Receptors: Ventricular mechanoreceptors and chemoreceptors

• Stimulus: Inferior myocardial infarction, underfilled ventricle

• Response: Bradycardia, hypotension, peripheral vasodilatation

• Exam focus: Paradoxical bradycardia in myocardial ischaemia

4) Cushing reflex

• Stimulus: Raised intracranial pressure

• Features: Hypertension, bradycardia, irregular respiration

• Exam focus: Late sign of raised ICP due to reduced cerebral perfusion

5) Peripheral chemoreceptor reflex

• Receptors: Carotid and aortic bodies

• Stimulus: Hypoxia (most sensitive), hypercapnia, acidosis

• Response: Increased ventilation and sympathetic activity

• Exam focus: Hypoxia is the dominant driver, not carbon dioxide

One-glance comparison table

Reflex	Primary trigger	Heart rate	Blood pressure	Classic clue
Baroreceptor	↑ / ↓ BP	↓ with ↑BP	Normalised	Postural change
Bainbridge	↑ Venous return	↑	Minimal change	Rapid IV fluids
Bezold–Jarisch	Ventricular ischaemia	↓	↓	Inferior MI
Cushing	↑ ICP	↓	↑	Head injury
Chemoreceptor	Hypoxia	↑	↑	Severe lung disease

The 5 most tested subtopics

1. Postural hypotension and baroreceptor compensation

2. Short-term vs long-term blood pressure control

3. Reflex bradycardia in myocardial infarction

4. Raised intracranial pressure physiology

5. Autonomic balance (sympathetic vs parasympathetic)

The 5 common exam traps

1. Assuming baroreceptors regulate chronic hypertension

2. Confusing Bainbridge reflex with baroreceptor reflex

3. Expecting tachycardia in all myocardial infarctions

4. Forgetting respiration in the Cushing reflex

5. Overlooking hypoxia as the key chemoreceptor stimulus

Practical examples / mini-cases

Mini-case 1

A 65-year-old man with an inferior ST-elevation myocardial infarction develops sudden bradycardia and hypotension.

Best explanation: Activation of ventricular receptors causing the Bezold–Jarisch reflex. Why this matters: MRCP Part 1 often tests unexpected bradycardia where candidates assume sympathetic activation.

Mini-case 2 (MCQ-style)

A patient stands abruptly from a supine position. Which mechanism prevents a sustained fall in blood pressure?

Correct answer: Arterial baroreceptor reflex. Explanation: Rapid autonomic adjustment increases heart rate and peripheral resistance to maintain cerebral perfusion.

You can practise similar applied questions using the Crack Medicine MRCP QBank and assess exam readiness with full mock tests.

Practical study-tip checklist

• Use a fixed template: stimulus → receptors → response

• Always predict heart rate first, then blood pressure

• Link each reflex to a clinical scenario

• Revise tables in the final week for rapid recall

• Practise timed MCQs to avoid overthinking simple physiology

Common pitfalls (5 bullets)

• Memorising lists without understanding physiology

• Ignoring time course (immediate vs delayed responses)

• Mixing atrial and ventricular stretch reflexes

• Forgetting that multiple reflexes may coexist

• Over-focusing on rare reflexes instead of core ones

FAQs

Are cardiovascular reflexes high yield for MRCP Part 1?

Yes. They are frequently tested because they integrate physiology with clinical medicine in short, efficient questions.

Do I need to memorise detailed pathways?

No. Focus on triggers, autonomic response, and net haemodynamic effect rather than detailed neuroanatomy.

Which reflexes should I prioritise?

Baroreceptor, Bainbridge, Bezold–Jarisch, Cushing, and peripheral chemoreceptor reflexes cover most exam questions.

How are these questions usually framed?

As brief clinical vignettes asking you to predict heart rate or blood pressure changes.

Ready to start?

For structured, exam-oriented revision, start with the MRCP Part 1 overview, practise with Free MRCP MCQs, and benchmark your progress using mock tests. Deeper explanations are available in our clinician-led MRCP lectures.

Sources

• MRCP(UK). Part 1 Examination Information. https://www.mrcpuk.org/mrcpuk-examinations/part-1

• Guyton AC, Hall JE. Textbook of Medical Physiology. Elsevier.

• Boron WF, Boulpaep EL. Medical Physiology. Elsevier.