Physiology Lab: Heart Sounds

What happens during ventricular diastole?

(1) Blood is returning to the heart. Oxygenated blood from the lungs enters the left atrium, and flows into the left ventricle through the open AV valve.

What happens during atrial systole?

(2) Filling of the ventricles is completed when the atria contract. In the resting state, atrial systole accounts for 20% of ventricular filling.

What happens during ventricular systole?

(3) After the atria contract, ventricular contraction occurs. Initially, as the ventricles begin to contract, the pressure in them rises and exceeds that in the atria to close the AV valves. The volume of the ventricles cannot change until the pressure in the left ventricle exceeds that in the aorta and in the right ventricle exceeds that in the main pulmonary artery (isovolumic phase of ventricular contraction). When the pressure in the left ventricle finally exceeds that in the aorta (and the pressure in the right ventricle exceeds that in the main pulmonary artery), the semilunar valves open, and blood is ejected into the aorta and main pulmonary artery. As the ventricular muscle relaxes, pressures in the ventricles fall below those in the aorta and main pulmonary artery, and the semilunar valves close. Ventricular pressure continues to fall and when it has fallen below that in the atria, the AV valves open and filling begins again (ventricular diastole).

Aortic stenosis

A narrowed aortic valve impedes blood flow into the aorta during ventricular systole. This results in a characteristic systolic murmur that increases in loudness to midsystole and then fades gradually. The second heart sound may be softer than normal too.

Mitral stenosis

A narrowing of the orifice of the mitral valve. Blood flows from left atrium to left ventricle through this valve during ventricular diastole. With mitral stenosis, a low pitched, middiastolic murmur is heard. There is often a louder than normal first sound as the mitral valve is shut more forcefully than normal.

What is a PCG?

A phonocardiogram. The heart sound can be recorded using a cardiomicrophone and a PCG recording can be made. Brie

The defective valve does not close properly so blood flows back into the ventricle during early diastole. This results in an early diastolic murmur that follows the second heart sound and gradually decreases in intensity.

Aortic regurgitation

The defective valve impedes blood flow during ventricular systole. This results in a characteristic systolic murmur that increases in loudness to mid-systole and then fades gradually. The second heart sound may be softer than normal too.

Aortic stenosis

What do semilunar valves do?

Between the ventricle and artery. They prevent backflow of blood from the aorta and main pulmonary artery into the respective ventricle. Produce the higher-pitched "dub" sound.

Briefly explain how blood moves through the heart:

Blood enters the atrial chambers of the heart at a low pressure, and leaves the ventricles at a higher pressure. The high atrial pressure provides the energy to force blood through the circulatory system. Blood returning from the body arrives at the right side of the heart and is pumped through the lungs. Oxygen is picked up and COs is released. This oxygenated blood then arrives at the left side of the heart before it is pumped back to the body.

Mitral insufficiency

Damage to the valve structure leads to a leak of blood back from the contracting ventricle to the left atrium. This leak results in a high-pitched murmur heard throughout systole. Because of the greater blood volume in the left atrium, there is a very rapid filling of the left ventricle when the mitral valve opens in early diastole. This gives rise to a third heart sound.

What produces a heart murmur, and how can one be detected?

Malfunctions of the heart valves can often produce a murmur, which can be detected with a stethoscope.

Damage to the valve structure leads to a leak of blood from the contracting ventricle. This leak results in a high-pitched murmur heard throughout systole. There may also be a third heart sound.

Mitral regurgitation

There is a narrowing of the orifice of the valve. A low pitched, mid-diastolic murmur is heard. There is often a louder than normal first sound as the valve is shut more forcefully than normal.

Mitral stenosis

What is the difference between systole and diastole?

Systole is the phase of the heartbeat when the heart muscle contracts and pumps blood from the chambers into the arteries. Diastole is the phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood.

Explain briefly how the "lub-dub" sound occurs:

The "lub" sound is produced by the closure of the AV (mitral and tricuspid) valves. When the ventricles relax, the BP frops below that in the artery, and semilunar valves (aortic and pulmonary) close, producing the "dub" sound.

What is happening when heart sounds occur?

The closure of heart valves.

Aortic insufficiency

The defective valve does not close properly so that, during early diastole, blood flows back into the ventricle. This results in an early diastolic murmur that follows the second heart sound and gradually decreases in intensity.

What do the two valves of the heart do?

They convert the rhythmic contractions into a unidirectional pumping.

Why do the heart valves close automatically?

They do this whenever there is a pressure difference across the valve that would otherwise cause backflow of blood.

What do atrioventricular (AV) valves do?

They prevent backflow from ventricle to atruim. Consist of the mitral and tricuspid valves. Produce the lower pitched "lub" sound.

Which of the following is responsible for generating the first heart sound? a) Closing of the AV valves. b) Closing of the semilunar valves. c) Opening of the AV valves. d) Opening of the semilunar valves.

a) Closing of the AV valves.

Which of the following is responsible for generating the second heart sound? a) Closing of the AV valves. b) Closing of the semilunar valves. c) Opening of the AV valves. d) Opening of the semilunar valves.

b) Closing of the semilunar valves.

The QRS complex in the ECG occurs: a) After the first heart sound is heard. b) At the same time as the first heart sound is heard. c) At the same time as the second heart sound is heard. d) Before the first heart sound is heard.

d) Before the first heart sound is heard.

In the ECG of a normal cardiac cycle, the T wave corresponds to: a) Depolarization of the atria. b) Depolarization of the ventricles. c) Repolarization of the atria. d) Repolarization of the ventricles.

d) Repolarization of the ventricles.

Which statement correctly describes the cardiac cycle's two phases? a) Diastole - atria relax; systole - ventricles relax. b) Diastole - ventricles contract; systole - ventricles relax. c) Systole - atria contract; diastole - ventricles contract. d) Systole - atria relax; diastole - atria contract. e) Systole - ventricles contract; diastole - ventricles relax.

e) Systole - ventricles contract; diastole - ventricles relax.