The Structure And Function Of The Heart

Question 1

What is the flow of blood through the heart?

Answer 1

Vena cava(brings deoxygenated blood)-> right atrium-> (AV valve)->right ventricle-> (SL valve)->pulmonary artery(takes blood to lungs)->pulmonary vein(returns oxygenated blood)->left atrium->(AV valve)->left ventricle->(SL valve)->aorta(exits heart through aorta to body)

Question 2

What is cardiac output?

Answer 2

The volume of blood pumped through each ventricle per minute
Normal values(5litres/min)
Varies between individuals depends on physical fitness and level of activity

Question 3

How do you calculate cardiac output?

Answer 3

CO=HRxSV
CO- cardiac output(litres/min)
HR- heart rate(bpm)
SV- stroke volume(ml or l)

Question 4

What is the heart rate?

Answer 4

The number of heart beats per minute(pulse)

Question 5

What is the stroke volume?

Answer 5

The volume of blood expelled by each ventricle contraction

Question 6

What volume do the left and right atrium pump?

Answer 6

They pump the same volume of blood through the aorta and the pulmonary artery

Question 7

What do valves do?

Answer 7

Prevent the back flow of blood

Question 8

What are the two types of valves in the heart?

Answer 8

Atrioventricular valves(AV valves)
Semilunar valves(SL valves)

Question 9

Where are the atrioventricular valves located and what do they do?

Answer 9

They’re located at the bottom of the atria(between atria and ventricles) and control the flow of blood between the atria and the ventricles(prevent back flow of blood into atria)

Question 10

Where are the semilunar valves located and what do they do?

Answer 10

They’re located at the top of the ventricles(start of the arteries) and control the flow of blood between the ventricles and blood vessels(open during ventricular contractions allowing blood to flow to the arteries)

Question 11

What is each heartbeat called and what does it consist of?

Answer 11

Each heartbeat is called a cardiac cycle
This consists of a pattern of relaxation(diastole)- all chambers
And contraction(systole)- atria and ventricular

Question 12

What is systole?

Answer 12

The contraction of the heart(atrial first then ventricular), blood forced out of chambers

Question 13

What is diastole?

Answer 13

Relaxation of the heart, chambers fill with blood

Question 14

What happens during the cardiac cycle?

Answer 14

During atrial and ventricular diastole, blood returning to the atria flows into the ventricles
Atrial systole transfers the remainder of the blood through the atrio-ventricular (AV) valves to the ventricles
Ventricular systole closes the AV valves and pumps blood out through the semi lunar (SL) valves to the aorta and pulmonary artery
In diastole the higher pressure in the arteries closes the SL valves

Question 15

What does the opening and closing of the valves give?

Answer 15

It gives the heart its familiar beating noise/sounds heard with a stethoscope

Question 16

What happens to blood pressure in the aorta during the cardiac cycle?

Answer 16

It changes in the aorta during the cardiac cycle
It increases during ventricular systole and decreases during diastole

Question 17

Where do the heart beats originate?
What is the heart regulated by?

Answer 17

In the heart itself
It’s regulated by the nervous system and hormone

Question 18

How are contractions of the heart coordinated to allow it to function efficiently?

Answer 18

Sinoatrial node (SAN)/pacemaker
Atrioventricular node (AVN)
Conducting fibres

Question 19

What is the cardiac conducting system?

Answer 19

The auto rhythmic cells of the sino-atrial node (SAN) or pacemaker, located in the wall of the right atrium set the rate at which the heart contracts

Question 20

What happens during the cardiac conducting system?
(What causes systole)
(Ensures ventricular systole happens later than atrial systole)

Answer 20

The timing of the cardiac muscle cell contraction is controlled by the impulses from the SAN spreading through the atria causing atrial systole
This wave of excitement then travels to the atria-ventricular node (AVN), located at the centre of the heart
Impulses from the AVN travel down fibres in the central wall of the heart and then up through the walls causing ventricular systole

Question 21

What do the impulses in the heart generate?

Answer 21

Currents that can be detected by an electrocardiogram (ECG)

Question 22

What are the three waves a normal ECG pattern consists of?

Answer 22

P-wave of impulse over the atria(atrial systole)
QRS-wave over the ventricles(ventricular systole)
T-electrical recovery of ventricles at the end of systole(ventricular diastole)

Question 23

What do normal ECGs show?

Answer 23

Sinus rhythm- this is a repeat of the PQRS and T waves in a coordinated order

Question 24

What are the three abnormal ECGs?

Answer 24

Atrial flutter
Ventricular fibrillation
Ventricular tachycardia

Question 25

What is atrial flutter?

Answer 25

Excited heart, rapid contraction in either the atria or the ventricles, lots of P waves

Question 26

What is ventricular fibrillation?

Answer 26

Different groups of muscle contracting at the same time, loss of coordination, lethal if not corrected

Question 27

What is ventricular tachycardia?

Answer 27

Ventricles are contracting independently, pacemaker required to return heart beat to normal, no P waves, very fast heart beat more than 100 beats per minute

Question 28

How do you calculate heart rate?

Answer 28

By counting the number of cardiac cycles in a minute Divide the number of seconds it takes to complete one cycle by 60 60/0.6 etc

Question 29

What does the autonomic system do?

Answer 29

Regulates the functions of our internal organs(heart, intestines, stomach)

Question 30

What does the medulla regulate?

Answer 30

The medulla(located in the brain) regulates the rate of the sino-atrial node through the antagonistic action of the autonomic nervous system

Question 31

What are the two anatagonistic branches the autonomic nervous system consists of?

Answer 31

Sympathetic nervous system Parasympathetic nervous system

Question 32

What does the sympathetic nerve release?

Answer 32

It releases noradrenaline which increases the heart rate-fight or flight response

Question 33

What does the parasympathetic nerve release?

Answer 33

It releases acetylcholine which decreases heart rate-rest and digest response

Question 34

How is the rate of the heartbeat determined?

Answer 34

By which of the two sympathetic or parasympathetic exerts the greatest control

Question 35

How is blood pressure measured?

Answer 35

Using a sphygmomanometer Normal values 120/80mmHg

Question 36

What happens when you use a sphygmomanometer?

Answer 36

An inflatable cuff stops the blood flow in the artery and deflates gradually The blood starts to flow(detected by a pulse) at systolic pressure The blood flows freely through the artery(pulse not detected) at diastolic pressure

Question 37

What is hypertension?

Answer 37

Hypertension is high blood pressure It’s a major risk factor in many diseases such as stroke and coronary heart disease