3.1.5 Heart

Question 1

What do Atria do?

Answer 1

Receive blood

Question 2

What do ventricles do?

Answer 2

Pump blood

Question 3

What do the atrioventricular valves do?

Answer 3

They prevent the back flow of blood from the ventricle to the atria.

Question 4

What is the left valve called?

Answer 4

The bicuspid valve (has two flaps)

Question 5

What is the right valve called?

Answer 5

The tricuspid valve ( three flaps)

Question 6

What are the valves held in place by?

Answer 6

Valve tendons attached to papillary muscles.

Question 7

What do papillary muscles do?

Answer 7

They contract at the same time as the ventricles, holding the valves closed

Question 8

What are the two semi lunar valves and where are they?

Answer 8

Pulmonary and Aortic valves. Found in the arteries.

Question 9

What are the two halves of the heart separated by?

Answer 9

The Inter-ventricular septum

Question 10

Why are the walls of the right ventricle 3 time thinner than on the left and why does it produce less force/pressure?

Answer 10

Because the blood has less far to go because the lungs are near the heart, but also because a lower pressure in the pulmonary circulation means that less fluid passes from the capillaries to alveoli.

Question 11

What is cardiac muscle composed of?

Answer 11

Myocytes

Question 12

Explain the function of Myocytes in cardiac muscle.

Answer 12

When they receive an electrical impulse they contract causing a heartbeat. Since they are constantly active they require a lot of oxygen which is supplied by capillaries from the two coronary arteries

Question 13

What does it mean for cardiac muscle to be myogenic?

Answer 13

It can contract on its own without electrical impulses

Question 14

How are contractions initiated in the heart?

Answer 14

Through the sino-atrial node in the right atrium

Question 15

What are the three stages of the cardiac cycle?

Answer 15

• Atrial systole
• Ventricular systole
• Diastole

Question 16

Explain Atrial Systole

Answer 16

The SAN contracts and sends impulses through both atria which also contract, pumping blood into the ventricles, which don’t contract because they are electrically insulated from the atria. Blood cannot flow back due to the valves

Question 17

Explain ventricular systole

Answer 17

The impulse from the SAN passes through the Atrioventricular node to the Purkinje fibres with a delay of 0.1 seconds, the fibres pass down through the interventricular septum as an electrically insulated bundle of His, which spread out at the base of the ventricle and initiate contraction. The ventricles contract from bottom up pushing blood into the arteries but not the atria due to the atrioventricular valve which makes a lub sound

Question 18

Explain Diastole

Answer 18

The atria and ventricles relax while the atria fill with blood. The semi lunar valves in the arteries close as the blood in the arteries pushes against them making a ‘dup’ sound

Question 19

How does atrial systole cause blood to flow into the ventricles?

Answer 19

Blood always flows from an area of high pressure to lower pressure, so when the atria contracts it increases the pressure inside the atria, causing blood to flow to the lower pressure ventricles.

Question 20

Why does blood not flow from the arteries into the atria if arterial blood pressure is significantly higher than in the atria?

Answer 20

The semi lunar valves stop blood flowing back into the heart

Question 21

What does lines intersecting in a heart pressure graph indicate?

Answer 21

Valves opening or closing

Question 22

What is a PCG/Phonocardiogram?

Answer 22

A recording of the sounds the heart makes in the cardiac cycle

Question 23

What is an ECG/Electrocardiogram?

Answer 23

Recording of the electrical impulse of the electrical activity of the heart.

Question 24

What is Cardiac output and how is it measured?

Answer 24

The amount of blood flowing through the set per minute: heart rate * stroke volume.

Question 25

What is heart rate?

Answer 25

Number of beats per minute, calculated by dividing 60 by the time taken for one cardiac cycle on the pressure graph.

Question 26

What is stroke volume?

Answer 26

The volume of blood pumped in each beat

Question 27

What are the effects of increased cardiac output from exercise?

Answer 27

- oxygen and glucose gets to the muscles faster - co2 and lactate can be carried away from the muscles faster - heat can be carried away from the muscles faster

Question 28

What is coronary heart disease?

Answer 28

A blockage in the coronary blood system that inhibits supply of oxygen to cardiac cells, killing them, which may cause a heart attack

Question 29

What is the coronary blood system?

Answer 29

The system that feeds oxygenated blood to the cardiac system allowing it to respire at contract, as cardiac cells cannot anaerobically respire.

Question 30

What causes coronary heart disease?

Answer 30

Cholesterol and other insoluble lipids collecting on the inside of a coronary artery, creating an atheroma which causes atherosclerosis - restriction of blood flow through narrowing the lumen.

Question 31

What happens after an atheroma causes atherosclerosis in the coronary artery?

Answer 31

The atheroma collects minerals from the blood and becomes a hard plaque, which weakens the wall of the artery.

Question 32

What is the possible consequence of plaque wearing the walls of a coronary artery?

Answer 32

The high blood pressure in arteries can cause the weakened area to swell, causing an aneurysm. If the wall is weak enough, the vessel will burst, causing blood loss and eventual death.

Question 33

What will plaque in an artery do apart from weakening the walls of the artery?

Answer 33

It can encourage the formation of a blood clot called a thrombus, or a mobile blood clot from elsewhere called an embolism can be caught in the atheroma. The clot grows until it totally blocks the artery causing coronary thrombosis.

Question 34

What is the effect coronary thrombosis has on the body?

Answer 34

It starves the cardiac cells downstream of the blockage so they cannot respire and die. The death of these Myocytes causes myocardial infarction (heart attack). The severity of the attack is dependant on Where the blockage is located.

Question 35

Explain the five stages of a heart attack

Answer 35

- Formation of atheroma - Hardening into plaque - Aneurism due to weak walls OR - Coronary Thrombosis from clot blockage - Myocardial Infarction due to death of cardiac cells

Question 36

What are the risk factors for CHD/Coronary Heart Disease?

Answer 36

- Smoking - Diet - Genetics - Blood Pressure - Blood cholesterol

Question 37

How is smoking a risk factor for CHD?

Answer 37

The carbon monoxide and nicotine from smoking increases blood pressure

Question 38

How is diet a risk factor for CHD?

Answer 38

High levels of saturated fat increase the cholesterol levels in the blood, increasing the risk of atherosclerosis. Salt increases blood pressure

Question 39

How is genetics a risk factor for CHD?

Answer 39

Blood pressure and fat metabolism are both genetic.

Question 40

How is blood pressure a risk factor for CHD?

Answer 40

Higher blood pressure makes an aneurysm more likely and stimulates thickening of arterial walls increasing risk of thrombosis

Question 41

How is blood cholesterol a risk factor for CHD?

Answer 41

Cholesterol is carried in lipoproteins. High density lipoproteins (HDL) remove cholesterol from tissue, decreasing risk of atherosclerosis. Low density lipoproteins (LDL) deliver cholesterol to tissues and increase the risk the atherosclerosis.

Question 42

How many chambers does the human heart have, and what are they called?

Answer 42

4. 2 Atria on top and 2 Ventricles on bottom

Question 43

The cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN). Describe how.

Answer 43

SAN initiates the heartbeat and sends an impulse causing the atrial contraction The AVN the delays the impulse allowing the ventricles to fill with blood before they contract AVN then sends an impulse down the bundle of His causing the ventricle to contract