the heart

Question 1

explain where oxy/deoxy blood flows in the heart

Answer 1

• deoxygenated blood flows into right side of the heart and then to the lungs
• oxygenated blood from lungs returns to left side of the heart

Question 2

what is the heart made from

Answer 2

myogenic cardiac muscle

Question 3

what artery supplies the heart

Answer 3

coronary artery supplies oxygenated blood

Question 4

what is the heart surrounding by and what do they do?

Answer 4

inelastic pericardial membranes - prevent over-distending

Question 5

what is meant by ‘over-distending with blood’

Answer 5

when pressure in blood vessels is too high for a long period of time

Question 6

which side of the heart has thicker muscular walls?

Answer 6

the left side

Question 7

why does the left side of the heart have thicker muscular walls than the right?

Answer 7

• right side has to pump blood a relatively short distance
• left has to provide sufficient force to overcome resistance of the aorta and arterial systems to move blood under pressure to all extremities of the body

Question 8

what is the septum?

Answer 8

the inner dividing wall of the heart

Question 9

what is the role of the septum?

Answer 9

prevents mixing of deoxygenated and oxygenated blood

Question 10

what is a heart murmur

Answer 10

when there is a hole in the septum of the heart

Question 11

what causes a heart murmur?

Answer 11

• septum does not fully develop until after birth
• blood is oxygenated by the placenta, not lungs (in fetus)
• blood in the heart is very similar so mixes freely
• days after birth, septum closes to ensure separation of blood
• a gap in the septum after the first few weeks of life is a murmur

Question 12

how long does the cardiac cycle last in adults?

Answer 12

0.8s

Question 13

what happens during diastole?

Answer 13

the heart relaxes - atria and then ventricles fill with blood, volume and pressure of blood builds as the heart fills, but arterial pressure is at a minimum

Question 14

what happens during systole?

Answer 14

the atria contract (atrial systole), followed by the ventricles (ventricular systole)
- pressure inside the heart increases dramatically as blood is forced to the lungs (right) and to main body circulation (left)
- volume and pressure of blood in heart are low at end of systole, pressure in arteries is at a max.

Question 15

what creates the ‘lub’ sound in the cardiac cycle?

Answer 15

blood is forced against atrio-ventricular valves as ventricles contract

Question 16

what creates the ‘dub’ sound in the cardiac cycle?

Answer 16

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

Question 17

what is meant by myogenic?

Answer 17

it has its own intrinsic rhythm by initiating its own electrical impulses

Question 18

why does the heart have an average rhythm? what is it?

Answer 18

prevents body wasting resources by maintaining the basic heart rate - 60bpm

Question 19

what 3 factors can affect heart rate?

Answer 19

• exercise
• excitement
• stress

Question 20

explain how the basic rhythm of the heart is maintained

Answer 20

• sino-atrial node (SAN) begins wave of electrical excitation - causes atria to contract - non-conducting tissue prevents excitation passing into the ventricles
• electrical activity is picked up by atrioventricular node (AVN) that imposes slight delay before stimulating bundle of His
• bundle of His splits into two branches and conducts wave of excitation to apex
• purkyne fibres at apex spread through ventricle walls, spread of excitation stimulates ventricle contraction (starting at the apex)

Question 21

what does the SAN do?

Answer 21

initiates electrical impulses to start atrial systole/contractions

Question 22

what does the AVN do?

Answer 22

delays the signal from the SAN - allows atria to contract fully to allow blood to complete flow into ventricles

Question 23

what is the bundle of His composed of?

Answer 23

purkyne fibres

Question 24

what does the bundle of His do?

Answer 24

transmits impulses from AVN to apex of the heart

Question 25

what are purkyne fibres

Answer 25

fibres that penetrate through the septum between ventricles

Question 26

what does ventricle contraction start at the apex of the heart?

Answer 26

ensures all the blood in the ventricles can be pumped out

Question 27

why does the AVN cause a delay?

Answer 27

to ensure atria have stopped contracting before ventricles start

Question 28

what does an electrocardiogram (ECG) do

Answer 28

measures electrical heart activity

Question 29

what is tachycardia?

Answer 29

rapid heartbeat - over 100bpm

Question 30

what is bradychardia?

Answer 30

slow heartbeat (below 60bpm)

Question 31

what is an ectopic heartbeat

Answer 31

extra heartbeats, out of regular rhythm

Question 32

what is atrial fibrilation

Answer 32

example of an arrhythmia (abnormal heart rhythm)