2.6. The Structure and Function of the Heart

Question 1

What is the pathway of the systemic circulation part of the bloodflow?

Answer 1

Left Ventricle -> Aorta -> Body -> Vena Cava -> Left Atrium ->….

Question 2

What is the pathway of the pulmonary circulation part of the bloodflow?

Answer 2

Right Ventricle -> Pulmonary Artery -> Lungs -> Pulmonary Vein -> Right Atrium ->…

Question 3

What are the atrio-ventricular valves?

Answer 3

The valves between the atria and the ventricles (2 of them).

Question 4

What is the aortic valve?

Answer 4

The valve between the left ventricle and the aorta.

Question 5

What is the pulmonary valve?

Answer 5

The valve between the right ventricle and the pulmonary artery.

Question 6

What is stroke volume?

Answer 6

The volume of blood ejected by each ventricle during each contraction.

Question 7

How do you calculate cardiac output?

Answer 7

Stroke volume x Heart rate

Question 8

What does systole mean?

Answer 8

When the heart chambers are contracted and blood is forced out of them. (Atria contract first, then ventricles).

Question 9

What does diastole mean?

Answer 9

When the chambers relax and the atria fill with blood.

Question 10

Describe atrial and ventricular diastole.

Answer 10

Blood flows into the left atrium from the pulmonary vein and the right atrium from the vena cava. Increased pressure in the atria open the atrio-ventricular valves where blood flows into them and the two semilunar valves are closed (pulmonary and aortic valve).

Question 11

Describe atrial systole.

Answer 11

This is when the atria contract and force the remaining blood in them through the atrio-ventricular valves into the ventricles. The ventricles are now full and the semi-lunar valves are still closed.

Question 12

Describe ventricular systole.

Answer 12

This is when the ventricles contract, closing the AV valves. The SL valves open and blood is pumped out of the heart into the arteries.

Question 13

What does SAN stand for and what is its function?

Answer 13

SAN stands for sino-atrial node and is also known as the pacemaker. It is situated in the wall of the right atrium and sends out impulses which are carried through the heart’s muscular walls of both of the atria. It also ensures that both the atria contract simultaneously.

Question 14

What does AVN stand for and what is its function?

Answer 14

After atrial systole the ATRIO-VENTRICULAR NODE picks up the same impulse from the SAN. The impulses then travel down the septum, branch of to the left and right passing through fibres in the outer walls before causing the ventricles to contract from the bottom up.

Question 15

What is the system called which causes the heart to contract?

Answer 15

The cardiac conducting system.

Question 16

What does ECG stand for and what does it do?

Answer 16

ECG stands for electrocardiogram and they are graphs which pick up the impulses the SAN sends out. They are picked up by putting electrodes on different areas of the body. They are used to identify heart problems such as a heart attack.

Question 17

How does the medulla regulate the rate of the SAN?

Answer 17

Through the antagonistic action of the autonomic nervous system.

Question 18

What are sympathetic nerves?

Answer 18

Nerves that accelerate the heart and strength of contractions. They also release nor-adrenaline. These fibres can be activated by stress and fear.

Question 19

What are parasympathetic nerves?

Answer 19

Nerves that slow the heart and release acetylcholine. These fibres are activated during rest.

Question 20

What is the most common instrument for measuring blood pressure?

Answer 20

Sphygmomanometer.

Question 21

What is hypertension?

Answer 21

High-blood pressure.