Which reflex explains the heart rate increase during rapid venous return on a tilt table?

• A. Bainbridge reflex
• B. Baroreceptor reflex
• C. Bezold-Jarisch reflex
• D. Coronary reflex

Answer: (A)

Rapid venous return increases filling of the right atrium, stretching its walls. This atrial stretch activates receptors that trigger the Bainbridge reflex, which raises heart rate by increasing sympathetic drive to the SA node. The goal is to boost cardiac output to handle the sudden surge in venous return, such as when a person is rapidly upright on a tilt table. The other reflexes don’t fit this situation: the baroreceptor reflex mainly adjusts heart rate in response to changes in arterial pressure (often slowing the heart if pressure rises), the Bezold-Jarisch reflex tends to cause bradycardia and vasodilation under certain conditions, and the coronary reflex mainly affects coronary blood flow rather than directly increasing heart rate in response to atrial stretch.