Cardiovascular reflexes: Bainbridge reflex: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Cardiovascular reflexes: Bainbridge reflex

Sample item

A rapid intravenous saline infusion raises right atrial pressure in a healthy volunteer, and the heart rate increases even though arterial pressure is unchanged. Which reflex is responsible?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Atrial stretch receptors acting through vagal afferents to increase sympathetic drive to the sinus node

The Bainbridge reflex is a rise in heart rate when atrial stretch receptors are stimulated by increased venous return. Afferents travel in the vagus to the medulla, and the efferent response is reduced vagal and increased sympathetic activity at the sinus node. It tends to prevent blood from pooling in the great veins.

Option by option

  • A. Carotid baroreceptor unloading reducing vagal tone

    Arterial pressure is unchanged, so baroreceptors are not unloaded.

  • B. Chemoreceptor stimulation by the saline load

    Chemoreceptors respond to oxygen, carbon dioxide and pH and not to saline load.

  • C. Atrial stretch receptors acting through vagal afferents to increase sympathetic drive to the sinus node (correct)

    Correct. Atrial stretch raises heart rate through a vagal-afferent, sympathetic-efferent reflex.

  • D. The Bezold-Jarisch reflex acting through cardiac chemoreceptor afferents

    The Bezold-Jarisch reflex causes bradycardia, hypotension and apnoea, not tachycardia.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, Atrial stretch receptors acting through vagal afferents to increase sympathetic drive to the sinus node. The Bainbridge reflex is a rise in heart rate when atrial stretch receptors are stimulated by increased venous return.

Why is "Carotid baroreceptor unloading reducing vagal tone" not the answer?

Arterial pressure is unchanged, so baroreceptors are not unloaded.

Why is "Chemoreceptor stimulation by the saline load" not the answer?

Chemoreceptors respond to oxygen, carbon dioxide and pH and not to saline load.

Why is "The Bezold-Jarisch reflex acting through cardiac chemoreceptor affere…" not the answer?

The Bezold-Jarisch reflex causes bradycardia, hypotension and apnoea, not tachycardia.

What concept does this question test?

It tests Cardiovascular reflexes: Bainbridge reflex in Physiology. Afferents travel in the vagus to the medulla, and the efferent response is reduced vagal and increased sympathetic activity at the sinus node. It tends to prevent blood from pooling in the great veins.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Cardiovascular reflexes: Bainbridge reflex?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.