8.5: The Heart

Question 1

What type of muscle is the heart made of?

Answer 1

Cardiac muscle.

Question 2

What supplies the cardiac muscle with oxygenated blood?

Answer 2

Coronary arteries.

Question 3

What is the function of the coronary arteries?

Answer 3

To supply the cardiac muscle with the oxygenated blood that it needs to continue contracting and relaxing

Question 4

What is the name of the membrane that the heart is surrounded by?

Answer 4

Inelastic Pericardial Membranes

Question 5

What is the purpose of the inelastic pericardial membrane?

Answer 5

To prevent the heart from over-filling and over-stretching

Question 6

Do the atria have thick or thin muscle walls?

Answer 6

Thin

Question 7

Which side of the heart pumps oxygenated blood?

Answer 7

Left side

Question 8

What is the function of the atrio-ventricular valves?

Answer 8

-Open to let blood pass into the ventricles from the atria
-Close to prevent backflow of blood back to atria.

Question 9

What is the alternate name for bicuspid and tricuspid valves?

Answer 9

Atrioventricular valves

Question 10

What is the alternate name for atrioventricular valves?

Answer 10

Bicuspid and tricuspid valves

Question 11

Is the bicuspid valve in the left or right side of the heart?

Answer 11

Left

Question 12

How are atrioventricular valves attached to the walls of the ventricles?

Answer 12

By tendons

Question 13

What is the function of tendinous cords?

Answer 13

-Connects the atrioventricular valves to the ventricles
-Makes sure the valves are not turned inside out by the pressure exerted when the ventricle contracts

Question 14

Which side of the heart’s muscular wall is thicker: left or right?

Answer 14

Left

Question 15

Why does the left side of the heart’s muscular wall need to be thicker?

Answer 15

To provide sufficient force to:
-Overcome the resistance of the aorta and arterial systems of the whole body
-Move the blood under pressure to all the extremities of the body

Question 16

Why is the right side of the heart’s muscular wall not thick?

Answer 16

-Because the right side of the heart passes blood to the lungs, which are smaller than the rest of the body, and closer to the heart.
-The right side of the heart only has to overcome the resistance of pulmonary circulation

Question 17

What is the septum?

Answer 17

The inner dividing wall of the heart

Question 18

What is the function of the septum?

Answer 18

To prevent the mixing of oxygenated and deoxygenated blood

Question 19

When does the right atrioventricular valve open?

Answer 19

When slight pressure builds up in the right atrium

Question 20

When does the right atrioventricular valve close?

Answer 20

When the right ventricle starts to contract

Question 21

When does the atrium contract?

Answer 21

Once both the atrium and ventricle are filled

Question 22

When does the ventricle contract?

Answer 22

When there is no more blood in the atrium

Question 23

When does the semi-lunar valve open?

Answer 23

When the ventricle contracts

Question 24

What do semi-lunar valves do?

Answer 24

Prevent the backflow of blood back into the heart

Question 25

What is the cardiac cycle?

Answer 25

The events in a single heartbeat

Question 26

What are the two key parts of the cardiac cycle?

Answer 26

Diastole and Systole

Question 27

What happens during diastole?

Answer 27

The heart relaxes -Atria and ventricles fill with blood -Volume increases, pressure decreases (of blood) -Pressure in arteries is at a minimum

Question 28

What are the two parts of systole?

Answer 28

Atrial systole and ventricular systole

Question 29

What is cardial output?

Answer 29

Volume of blood pumped out of the heart during one minute

Question 30

What happens during systole

Answer 30

-First the atria contract (atrial systole), then the ventricles contract (ventricular systole) -Pressure inside the heart increases drastically, and blood is forced out of the heart. -Volume of blood in heart decreases -Pressure in the arteries is at a maximum

Question 31

By the end of systole, is the volume of blood in the heart high or low?

Answer 31

Low

Question 31

What is stroke volume?

Answer 31

The volume of blood pumped out by hte left ventricle in each beat.

Question 32

What is the equation for Cardial Output?

Answer 32

Cardian Output = Stroke Volume x Heartrate

Question 33

What is mass flow?

Answer 33

The bulk movement of blood from one part of the body to another as a result of pressure difference between the two points

Question 34

Which valve opens/closes when the pressure in the atrium is greater than the pressure in the ventricle?

Answer 34

The atrioventricular valve opens

Question 35

Which valve opens/closes when the pressure in the ventricle is greater than the pressure in the atrium?

Answer 35

The atrioventricular valve closes

Question 36

Which valve opens/closes when the pressure in the ventricle is greater than the pressure in the arteries?

Answer 36

The semilunar valve opens

Question 37

Which valve opens/closes when the pressure in the arteries is greater than the pressure in the ventricle?

Answer 37

The semilunar valve closes

Question 38

What is the general sound of the heart?

Answer 38

"Lub-dub"

Question 39

What does the "lub" sound of a heartbeat represent?

Answer 39

Blood is being forced against the atrioventricular valves as the ventricles contract

Question 40

What does the "dub" sound of a heartbeat represent?

Answer 40

Backflow of blood closes the semilunar valves in the aorta and pulmonary artery as the ventricles relax

Question 41

Why is the pressure in the atrium lower than the pressure in the left ventricle? (for what purpose)

Answer 41

-Because the ventricle has a thicker muscle wall and has to generate more force to force blood around the whole body -The atrium only has to force blood into the ventricle, aided by gravity (so less force is required)

Question 42

How does the structure of the aorta help to maintain a minimum pressure?

Answer 42

-Has strong elastic tissue, allowing it to stretch and recoil. -Recoiling reduces volume and increases pressure, creating a pulse and pushing the blood

Question 43

Why is atrial pressure relatively low?

Answer 43

Because the thin walls of the atrium cannot create much force

Question 44

Why does aortic pressure initially increase?

Answer 44

When the ventricles contract as blood is forced into the aorta

Question 45

What are the contractions of the cardiac muscle?

Answer 45

Myogenic

Question 46

What is the purpose of the cardiac muscle being myogenic?

Answer 46

Prevents the body wasting resources maintaining the basic heart rate

Question 47

What is the basic rhythm of the heart maintained by?

Answer 47

A wave of electrical excitation

Question 48

What does AVN stand for?

Answer 48

Atrioventricular node

Question 49

What does SAN stand for?

Answer 49

Sinoatrial node

Question 50

Where is the sinoatrial node located?

Answer 50

Wall of the right atrium

Question 51

State the process of electrical excitation of the heart (long answer)

Answer 51

-Sino-atrial node produces a wave of electrical excitation -Impulse spreads across both atria making them contract -Excitation transmitted to the atrioventricular node, and is delayed slightly -Electrical impulse passes from the AVN to the bundle of His, made of Purkyne fibres that pass through the septum -Bundle of His splits into 2 branches and conducts the wave to the bottom of the heart -Excitement spreads across both ventricles from the bottom to the top -Ventricles contract from the bottom upwards

Question 52

Why do the ventricles contract from the bottom upwards?

Answer 52

To ensure all the blood is forced out

Question 53

What is an alternative name to the bottom of the heart?

Answer 53

The apex

Question 54

What is the bundle of His made up of?

Answer 54

Purkyne fibres

Question 55

Why is there a layer of non-conducting tissue between the atria and the ventricles?

Answer 55

To ensure that the excitation is not passed onto the ventricles before the atria have fully contracted and emptied

Question 56

Why is the SAN called the natural pacemaker?

Answer 56

Because the rate at which the SAN produces the waves of electrical excitement determines the rate of the heartbeat

Question 57

What is an electrocardiogram?

Answer 57

A recording of the electrical activity of the heart

Question 58

What does an electrocardiogram measure?

Answer 58

Tiny electrical differences in your skin, which result from the electrical activity of the heart

Question 59

What are ECGs used for?

Answer 59

Recording electrical activity of the heart and diagnosing heart problems

Question 60

What does ECG stand for?

Answer 60

Electrocardiogram

Question 61

What are the letters representing different segments of an ECG?

Answer 61

P, Q, R, S, T

Question 62

What does the P wave of an ECG represent?

Answer 62

Wave of excitation passing to the atria, causing them to contract

Question 63

What does the QRS complex of an ECG represent?

Answer 63

Wave of excitation passing to the ventricles, causing them to contract

Question 64

What does the T wave of an ECG represent?

Answer 64

The heart relaxeing before the next heart beat, returning to its original state

Question 65

What does arrhythmia mean?

Answer 65

Abnormal rhythm of the heart

Question 66

What is Tachycardia?

Answer 66

Rapid heartbeat, still evenly spaced out

Question 67

What is the term for when your heartbeat is rapid?

Answer 67

Tachycardia

Question 68

What is bradycardia?

Answer 68

Slow heartbeat, still evenly spaced out

Question 69

What is the term for when your heartbeat is very slow?

Answer 69

Bradycardia

Question 70

What is an ectopic heartbeat?

Answer 70

When there are extra heartbeats that are out of the normal rhythm

Question 71

What is the term for when you have extra heartbeats that are out of the normal rhythm?

Answer 71

Ectopic heartbeat

Question 72

What is atrial fibrillation?

Answer 72

When rapid electrical impulses generated in the atria prevent atria from contracting properly and make the heart not pump blood efficiently