Chapter 19 The Circulatory System: Heart

Atrial contraction accounts for most of the ventricular filling. True False Most ventricular filling happens passively while the atrioventricular valves remain open in between ventricular contractions. Atrial contraction plays a small role in ventricular filling.

False

The atria never contract due to passive ventricular filling. True False The atria contract and are responsible for the active filling that takes place just before the ventricular contraction.

False

The beginning of ventricular systole is when blood flowing back toward the relaxed ventricles causes the semilunar valves to close. True False Ventricular systole begins when the ventricles begin to contract.

False

The ventricles begin to fill during ventricular diastole. True False Most ventricular filling happens passively while the atrioventricular valves remain open in between ventricular contractions, a time known as ventricular diastole.

True

In the heart, an action potential originates in the __________. 1. Purkinje fibers 2. bundle branches 3. atrioventricular bundle 4. atrioventricular node 5. sinoatrial node The normal heartbeat is triggered by autorhythmic cells in the right atrium called the sinoatrial node.

5. sinoatrial node

Which of the following is true concerning the heart's conduction system? 1. Action potentials pass slowly through the atrioventricular node. 2. Action potentials pass slowly through the atrioventricular bundle. 3. Action potentials pass slowly through the Purkinje fibers. 4. Action potentials pass slowly through the ventricle wall. 5. Action potentials pass slowly through the bundle branches. Firing of the SA node excites atrial cardiocytes and stimulates the two atria to contract almost simultaneously. The signal travels through the atrial myocardium and reaches the AV node. The signal at the AV node is delayed, giving the ventricles time to fill with blood before they begin to contract. Signals then travel through the AV bundle and Purkinje fibers. Consequently, the entire ventricular myocardium depolarizes within 200 ms after the SA node fires, causing the ventricles to contract in near unison. Signals reach the papillary muscles before the rest of the myocardium. Thus, these muscles contract and begin taking up slack in the tendinous cords an instant before ventricular contraction causes blood to surge against the AV valves. Ventricular systole begins at the apex of the heart, which is first to be stimulated, and progresses upward—pushing the blood upward toward the semilunar valves. Because of the spiral arrangement of ventricular cardiocytes, the ventricles twist slightly as they contract, like someone wringing out a towel.

1. Action potentials pass slowly through the atrioventricular node.

Which of the following is the correct sequential path of an action potential in the heart? 1. Sinoatrial node, atrioventricular node, atrioventricular bundle, bundle branches, Purkinje fibers 2. Atrioventricular node, sinoatrial node, atrioventricular bundle, bundle branches, Purkinje fibers 3. Atrioventricular bundle, atrioventricular node, sinoatrial node, bundle branches, Purkinje fibers 4. Purkinje fibers, atrioventricular bundle, atrioventricular node, sinoatrial node, bundle branches 5. Atrioventricular node, sinoatrial bundle, atrioventricular node, bundle branches, Purkinje fibers Firing of the SA node excites atrial cardiocytes and stimulates the two atria to contract almost simultaneously. The signal travels through the atrial myocardium and reaches the AV node. The signal at the AV node is delayed, giving the ventricles time to fill with blood before they begin to contract. Signals then travel through the AV bundle and Purkinje fibers. Consequently, the entire ventricular myocardium depolarizes within 200 ms after the SA node fires, causing the ventricles to contract in near unison. Signals reach the papillary muscles before the rest of the myocardium. Thus, these muscles contract and begin taking up slack in the tendinous cords an instant before ventricular contraction causes blood to surge against the AV valves. Ventricular systole begins at the apex of the heart, which is first to be stimulated, and progresses upward—pushing the blood upward toward the semilunar valves. Because of the spiral arrangement of ventricular cardiocytes, the ventricles twist slightly as they contract, like someone wringing out a towel.

1. Sinoatrial node, atrioventricular node, atrioventricular bundle, bundle branches, Purkinje fibers

The atrioventricular valves open during __________. 1. ventricular systole 2. ventricular diastole 3. atrial systole 4. atrial diastole 5. both atrial and ventricular systole The atrioventricular valves refer to the tricuspid and mitral valves. While the ventricles are relaxed, also known as ventricular diastole, the papillary muscles on the inside of the ventricles tug on the chordae tendineae, pulling the cusps of these valves to an open position.

2. ventricular diastole

The semilunar valves close during __________. 1. ventricular systole 2. ventricular diastole 3. atrial systole 4. atrial diastole 5. both atrial and ventricular systole The semilunar valves refer to the aortic and pulmonary valves. While the ventricles are relaxed, also known as ventricular diastole, the pressures in the ascending aorta and pulmonary trunk are greater than the pressures in the ventricles. Since these one-way valves open into the vessels, the pressure difference causes them to close.

2. ventricular diastole

Which of the following is the correct sequence of events regarding the cardiac cycle? 1. Isovolumic contraction, isovolumic relaxation, ejection, passive ventricular filling, active ventricular filling 2. Isovolumic relaxation, isovolumic contraction, ejection, passive ventricular filling, active ventricular filling 3. Isovolumic contraction, ejection, isovolumic relaxation, passive ventricular filling, active ventricular filling 4. Isovolumic contraction, ejection, isovolumic relaxation, active ventricular filling, passive ventricular filling 5. Ejection, isovolumic relaxation, passive ventricular filling, isovolumic contraction, active ventricular filling When the ventricles begin to contract, the volume of blood remains the same because the atrioventricular and semilunar valves are closed at the same time. This is isovolumetric contraction. Once the pressure opens the semilunar valves, blood is ejected. When the contraction ceases, the semilunar valves close and the atrioventricular remain closed, so the blood volume doesn't change. This is isovolumetric relaxation. At full relaxation, the atrioventricular valves open and blood passively travels from the atria to the ventricles. Finally, the atria contract and actively force the remaining atrial blood into the ventricles.

3. Isovolumic contraction, ejection, isovolumic relaxation, passive ventricular filling, active ventricular filling

Which of the following is caused by ventricular contraction? 1. Blood flows into the ventricles. 2. Blood flows out of the atria. 3. The atrioventricular valves close, and then the semilunar valves open. 4. The semilunar valves close, and then the atrioventricular valves open. 5. Pressure becomes greater in the aorta and pulmonary trunk as compared to inside the ventricles. When the ventricles contract, the walls of the ventricles come together, releasing tension on the chordae tendineae. In addition, the pressure inside the ventricles greatly increases. The decrease in tension and the increase in pressure causes the atrioventricular valves to close. The increase in pressure also causes the semilunar valves to open into the ascending aorta and pulmonary trunk.

3. The atrioventricular valves close, and then the semilunar valves open.

Which of the following statements is not true regarding ventricular systole? 1. The ventricles contract. 2. The atrioventricular valves close. 3. The semilunar valves open. 4. The ventricles relax. 5. Blood flows through the aorta and the pulmonary trunk. Ventricular systole refers to the point in time when the ventricles are contracting.

4. The ventricles relax.

When the pressure in the ventricles becomes lower than the pressure in the atria, __________. 1. the ventricles contract 2. blood flows into the pulmonary trunk 3. blood flows into the aorta 4. the atrioventricular valves open 5. the semilunar valves open When the ventricles relax, the pressure inside the ventricles decreases and becomes less than that of the atria. The decrease in pressure helps to open the atrioventricular valves.

4. the atrioventricular valves open

Action potentials are carried by the Purkinje fibers from the bundle branches to the ventricular walls. True False Firing of the SA node excites atrial cardiocytes and stimulates the two atria to contract almost simultaneously. The signal travels through the atrial myocardium and reaches the AV node. The signal at the AV node is delayed, giving the ventricles time to fill with blood before they begin to contract. Signals then travel through the AV bundle and Purkinje fibers. Consequently, the entire ventricular myocardium depolarizes within 200 ms after the SA node fires, causing the ventricles to contract in near unison. Signals reach the papillary muscles before the rest of the myocardium. Thus, these muscles contract and begin taking up slack in the tendinous cords an instant before ventricular contraction causes blood to surge against the AV valves. Ventricular systole begins at the apex of the heart, which is first to be stimulated, and progresses upward—pushing the blood upward toward the semilunar valves. Because of the spiral arrangement of ventricular cardiocytes, the ventricles twist slightly as they contract, like someone wringing out a towel.

True

In the ventricles, the action potential travels along the interventricular septum to the apex of the heart, where it then spreads superiorly along the ventricle walls. True False Firing of the SA node excites atrial cardiocytes and stimulates the two atria to contract almost simultaneously. The signal travels through the atrial myocardium and reaches the AV node. The signal at the AV node is delayed, giving the ventricles time to fill with blood before they begin to contract. Signals then travel through the AV bundle and Purkinje fibers. Consequently, the entire ventricular myocardium depolarizes within 200 ms after the SA node fires, causing the ventricles to contract in near unison. Signals reach the papillary muscles before the rest of the myocardium. Thus, these muscles contract and begin taking up slack in the tendinous cords an instant before ventricular contraction causes blood to surge against the AV valves. Ventricular systole begins at the apex of the heart, which is first to be stimulated, and progresses upward—pushing the blood upward toward the semilunar valves. Because of the spiral arrangement of ventricular cardiocytes, the ventricles twist slightly as they contract, like someone wringing out a towel.

True