During atrial contraction, how does ventricular pressure compare to atrial pressure?

During atrial contraction, how does ventricular pressure compare to atrial pressure?

• A. Ventricular pressure is less than atrial pressure.
• B. Ventricular pressure is greater than atrial pressure.
• C. Ventricular pressure equals atrial pressure.
• D. Ventricular pressure varies independently of atrial pressure.

Answer: (A)

During atrial contraction the ventricles are still relaxed and filling, so their pressure is low. The atria contract to push blood into the ventricles, and because the ventricles have a lower pressure, blood flows from the atria into the ventricles through the open AV valves. This creates a pressure gradient with higher atrial pressure driving flow into the lower-pressure ventricles. Only when the ventricles start to contract does their pressure rise above the atrial pressure to close the AV valves. So, ventricular pressure is less than atrial pressure during atrial contraction.

During atrial contraction the ventricles are still relaxed and filling, so their pressure is low. The atria contract to push blood into the ventricles, and because the ventricles have a lower pressure, blood flows from the atria into the ventricles through the open AV valves. This creates a pressure gradient with higher atrial pressure driving flow into the lower-pressure ventricles. Only when the ventricles start to contract does their pressure rise above the atrial pressure to close the AV valves. So, ventricular pressure is less than atrial pressure during atrial contraction.