Which receptors are primarily involved in the atrial reflex?

Which receptors are primarily involved in the atrial reflex?

• A. Baroreceptors in the carotid sinus
• B. Receptors in the atria responding to venous return
• C. Chemoreceptors in the aortic body
• D. Pacemaker cells in the ventricles

Answer: (B)

The atrial reflex is driven by stretch-sensitive receptors in the atrial walls, especially in the right atrium where venous return enters. When venous return increases, these atrial stretch receptors are activated and stimulate a reflex that raises heart rate. This helps match the heart’s output to the increased blood returning to the heart, preventing preload from becoming excessive. The signal travels to the brainstem and adjusts autonomic input to the SA node, increasing its firing rate. This is different from baroreceptors in the carotid sinus, which respond to arterial pressure changes and drive the baroreflex, or chemoreceptors in the aortic body, which detect changes in blood gases and pH. Ventricular pacemaker cells set the baseline rhythm but aren’t the receptors mediating this atrial stretch reflex. Thus, receptors in the atria responding to venous return are the primary players.

The atrial reflex is driven by stretch-sensitive receptors in the atrial walls, especially in the right atrium where venous return enters. When venous return increases, these atrial stretch receptors are activated and stimulate a reflex that raises heart rate. This helps match the heart’s output to the increased blood returning to the heart, preventing preload from becoming excessive. The signal travels to the brainstem and adjusts autonomic input to the SA node, increasing its firing rate.

This is different from baroreceptors in the carotid sinus, which respond to arterial pressure changes and drive the baroreflex, or chemoreceptors in the aortic body, which detect changes in blood gases and pH. Ventricular pacemaker cells set the baseline rhythm but aren’t the receptors mediating this atrial stretch reflex. Thus, receptors in the atria responding to venous return are the primary players.