Chapter S3, Problem 1.1A

Describe the actions of the frog heart chambers during a cardiac cycle.

Summary Introduction

To write:

The actions of the heart chambers during a cardiac cycle in frog.

Introduction:

Heart is the vital organ of the circulatory system as it pumps blood all over the body. Human heart consists of four chambers: two upper chambers or atria and two lower chambers or ventricles. Blood passes across a valve before parting each heart chamber.

Explanation of Solution

Heart of frog:

The heart in frog consists of three chambers. There are two atrial chambers which drain into a single and common ventricle.

The pacemaker in the frog’s heart is present in the posterior side of the heart. The pacemaker is known as the sinus venosus. This sinus venosus is similar to the sinoatrial node inside the cardiac tissue of human.

Actions of frog heart chambers during a cardiac cycle are:

There occurs an atrial systole or atrial contraction. Then there is an atrial diastole or relaxation. This diastole is followed by a ventricle systole. Then ventricular systole is followed by a ventricle diastole. These actions complete one heart beat in the frog.

Blood circulation in frog by the action of the heart chambers is:

  

The three chambers in the frog’s heart are two atria and one ventricle. Blood exits the heart by the ventricle across a single truncus arteriosus. It is a short blood vessel that immediately bifurcates into two aortic arches (left and right) dorsal to the heart. These aortic arches then reunite and form a single aorta in the mid-dorsal part of the body cavity. Each aortic arch gives off a branch that runs to the lungs and skin where the oxygenation of blood takes place. Carotid arteries also divide into the aortic arches. These deliver to the head region.

Veins transport blood back to the left and right atria. Both the atria then drain into a single ventricle. Then again the blood from the ventricle enters into the pulmocutaneous or body circulation. As, there exists a single ventricle, there occurs some mixing of the oxygenated and deoxygenated blood. Ventricular folds are present that prevent a complete combination of the venous and arterial blood.

So, actions of the chambers of the frog heart involve an atrial systole followed by an atrial diastole. Atrial diastole is then followed by a ventricle systole which is further followed by a ventricle diastole.

Conclusion

Hence, actions of the chambers of the frog heart during a cardiac cycle involve an atrial systole followed by an atrial diastole. Atrial diastole is then followed by a ventricle systole which is further followed by a ventricle diastole.