Control of Valve Function

Question 1

cardiac cycle (one complete heart beat)

Answer 1

pressure in the heart chambers increases and decreases.

When a chamber is empty - pressure decreases.

As a chamber fills - pressure increases.

sounds like “lub-dup”

Question 2

When atria relax

Answer 2

blood flows into them from the large attached veins.

As the atria fill, the pressure inside gradually increases, forcing the A-V valves open.

~70-80% of the entering blood flows directly into the ventricles before the atrial walls contract.

Then, during atrial contraction (atrial systole), atria pressure rises suddenly, forcing the remaining 20-30% of the atrial contents into the ventricles. Atrial relaxation (atrial diastole) follows.

Question 3

ventricles contract

Answer 3

the A-V valves close due to pressure differences between the ventricles and the atria and begin to bulge back into the atria, sharply increasing atrial pressure.

Question 4

Systole

Answer 4

contraction of a chamber; during systole, pressure within that chamber increases.

Question 5

Diastole

Answer 5

relaxation of a chamber; during diastole, pressure within that chamber decreases.

Question 6

Increasing pressure due to ventricular contractions

Answer 6

causes the A-V valves to close preventing backflow into the atria.

Question 7

papillary muscles contract

Answer 7

by pulling on the chordae tendineae, they prevent the cusps of the A-V valves from bulging too far into the atria, allowing atrial pressure to return to its previous level.

Question 8

ventricular contraction

Answer 8

the A-V valves remain closed, and atria pressure increases again as the atria fill with blood.

**When the ventricles relax (ventricular diastole), the A-V valves open, blood flows through them into the ventricles, and atrial pressure drops to a low point.

Question 9

Pressure in the ventricles

Answer 9

is low while they fill, but when the atria contract, ventricular pressure increases slightly.

Then, as the ventricles contract, ventricular pressure rises sharply, and as soon as the pressure exceeds that of the atria, the A-V valves close.

• Ventricular pressure continues to increase until it exceeds the pressure in the pulmonary trunk and aorta.
• Then, the pulmonary and aortic valves open, and blood is ejected from each valve’s respective ventricle into these arteries.
• When the ventricles are almost empty, ventricular pressure begins to drop, and it continues to drop as the ventricles relax.
• When ventricular pressure is less than that in the arteries, arterial blood flowing back toward the ventricles closes the pulmonary and aortic valves.
• As soon as ventricular pressure falls below that of the atria, the A-V valves open, and the ventricles begin to fill once more.

Question 10

heart chambers

Answer 10

chambers function in a coordinated fashion

• actions are regulated so that atrial walls contract while ventricular walls relax, then ventricular walls contract while atrial walls relax.

Question 11

Lub

Answer 11

ventricular contraction, when the A-V valves are closing.

(what you hear when listening to a heart beat)

**The beat heard is the result of ventricular action.

Question 12

Dup

Answer 12

ventricular relaxation, when the pulmonary and aortic valves are closing (snap shut)

Question 13

tachycardia

Answer 13

Rapid heart rate

Question 14

bradycardia

Answer 14

Slow heart rate

Question 15

arrhythmia

Answer 15

Irregular beat

Question 16

Coordinated fashion

Answer 16

• When atrial walls contract, ventricles relax

- When ventricular walls contract, atria relax