Vagal stimulation can cause bradycardia; which of the following is a vagal stimulus?

• A. Vomiting
• B. Caffeine intake
• C. Exercise
• D. High blood pressure

Answer: (A)

Vagal stimulation slows the heart by increasing parasympathetic activity to the heart’s SA and AV nodes, which reduces heart rate. Vomiting triggers a strong vagal reflex: signals from the GI tract reach the brainstem and boost parasympathetic outflow to the heart, often producing bradycardia. This makes vomiting a clear example of a vagal stimulus that can slow the heart, even leading to faintness in some vasovagal episodes.

The other options don’t fit as direct vagal triggers. Caffeine and exercise primarily activate the sympathetic system, raising heart rate. High blood pressure engages baroreceptor reflexes to counteract the rise, but it isn’t a direct vagal stimulus in the same way vomiting is.