The Heart and Cardiac Cycle

Question 1

Describe the walls if the atria.

Answer 1

Thin walled, elasticated, and stretch when they fill with blood.

Question 2

Describe the walls of the left ventricle.

Answer 2

Slightly thicker with more muscle so blood can be forced out of the heart to the rest of the body or lungs.

Question 3

What do valves do?

Answer 3

Prevent the backflow of blood back into the heart.

Question 4

What does the aorta do?

Answer 4

Carries oxygenated blood away from the heart towards the body.

Question 5

What does the vena cava do?

Answer 5

Carries deoxygenated blood back to the heart from the rest of the body.

Question 6

What does the pulmonary artery do?

Answer 6

Carries deoxygenated blood from the heart to the lungs.

Question 7

What does the pulmonary vein do?

Answer 7

Carries oxygenated blood from the lungs back to the heart.

Question 8

Where are the AV valves found?

Answer 8

Between the atria and ventricles.

Question 9

Where are semi lunar valves found?

Answer 9

Pulmonary artery
Aorta

Question 10

Why does the left ventricle have the most cardiac muscle?

Answer 10

To ensure the heart can withstand the high pressures needed to force blood out of the heart.

Question 11

Describe characteristics of the cardiac muscle.

Answer 11

Lots of myoglobin
Lots of mitochondria to release ATP for muscle contraction
Contracts involuntarily.

Question 12

Describe the human circulatory system.

Answer 12

Double.
The first circulatory system carries blood from the heart around the body.
The second circulatory system carries deoxygenated blood from the heart to the lungs.

Question 13

How does the heart receive a supply of oxygen?

Answer 13

Coronary arteries surround the heart to supply it with oxygen.

Question 14

What happens if the corornary arteries become blocked?

Answer 14

Blockages will prevent the heart from receiving a sufficient supply of oxygen, leading to heart attacks.

Question 15

What is a cardiac cycle?

Answer 15

A sequence of events that occurs within 1 heartbeat.

Question 16

What is diastole?

Answer 16

Relaxation of the heart.

Question 17

In diastole, what happens to pressure when the atria fill?
When do AV valves open and why?
Where does blood move from/to?

Answer 17

Pressure increases in the atria.
AV valves open once pressure in the atria is higher than in ventricles, so the ventricles fill.

Question 18

During diastole, what happens to ventricle walls and how does this change pressure?
Pressure in the ventricles is now _______ compared to which 2 vessels?
Which valves close next?

Answer 18

Ventricle walls relax. This causes them to recoil, reducing the pressure.
Pressure in the ventricles is now lower than in the aorta and pulmonary artery.
The semi lunar valves in the pulmonary artery and aorta shut.

Question 19

What is atrial systole?

Answer 19

Contraction of the atria.

Question 20

During atrial systole, which part of the heart contracts now?

Answer 20

Atrial walls.

Question 21

In atrial systole, what do the ventricle walls do?

Answer 21

They relax and recoil.

Question 22

In atrial systole, where does blood move from/to?
Which valves remain closed?

Answer 22

Any remaining blood from the atria is forced into the ventricle.
Semi lunar valves stay shut.

Question 23

What is ventricular systole?

Answer 23

Contraction of the ventricles.

Question 24

In ventricular systole, what happens to the ventricle walls as they fill with blood?

Answer 24

Ventricle walls contract.

Question 25

During ventricular systole, describe the pressure change in the ventricle.
Which valves shut and why?

Answer 25

Blood pressure in the ventricles increases which forces the AV valves to shut. This prevents back flow of blood into the heart.

Question 26

In ventricular systole, pressure in the ventricle must exceed pressure in which 2 blood vessels and why?

Answer 26

Pressure in the ventricles must exceed pressure in the aorta and pulmonary artery so blood can be forced into these vessels.

Question 27

In ventricular systole, to force blood out of the heart, which part of the heart contracts?

Answer 27

The ventricles contract forcefully, creating even higher pressure to force blood out of the heart.

Question 28

Describe how AV valves assist the cardiac cycle.

Answer 28

When ventricular pressure exceeds atrial pressure, closure of these valves ensures that blood within the ventricles is only forced out of the heart, not into the atria.

Question 29

Describe how semi lunar valves assist the cardiac cycle.

Answer 29

Prevents blood backflow when pressure in the pulmonary artery and aorta exceeds pressure in the ventricles.
This happens when the walls of the ventricles recoil and also when they relax.

Question 30

What is cardiac output?

Answer 30

The volume of blood pumped out of the heart within 1 minute.

Question 31

What are the units of measurement for the cardiac cycle?

Answer 31

dm^3 min^-1

Question 32

Give a formula linking cardiac output, stroke volume and heart rate.

Answer 32

Cardiac Output = Stroke Volume x Heart Rate

Question 33

What are artificial pacemakers used for?
Give 2 reasons why pacemakers in the heart stop working.

Answer 33

Used to regulate heartbeat when the heart can’t regulate itself.
They might be needed when the sinoatrial node is not working or a blockage between 2 AV valves may have occurred.

Question 34

How do artificial pacemakers work?

Answer 34

They monitor electrical activity of the heart and stimulate contraction of the atria and ventricles when needed.

Question 35

What does it mean to say the heart is myogenic?

Answer 35

Contraction is inherited from the heart muscle itself.

Question 36

Where is the hearts pacemaker (SAN) found?

Answer 36

In the right atrium wall.