Cardiac Cycle

Question 1

The basic rhythm of the heart is maintained by a wave of electrical excitation. What order does this wave travel through the heart?

Answer 1

1) Sinoatrial node (SAN) initiates heartbeat by stimulating atria to contract
2) Atrioventricular node (AVN)
3) Bundle of His - receives electrical activity from AVN and conducts wave to apex
4) Purkyne fibres - branch off bundle of his causing ventricles to contract

Question 2

What is the correct order: Ventricular systole, Diastole, Atrial systole

Answer 2

1) Atrial systole
2) Ventricular systole
3) Diastole

Question 3

What happens in atrial systole

Answer 3

• ventricles relax and atria contract
• atrial pressure increases
• atrioventricular valves (bicuspid & tricuspid) open
• blood flows into the ventricles

Question 4

What happens in ventricular systole

Answer 4

• ventricles contract, atria relax
• ventricular pressure increases
• semi-lunar valves open and atrioventricular (bicuspid & tricuspid) valves close
• blood flows into the arteries (pulmonary artery & aorta)

Question 5

What happens in diastole

Answer 5

• ventricles and atria relax
• semi-lunar valves close
• blood flows passively (via gravity) into atria

Question 6

What does ECG stand for and what is it

Answer 6

Electrocardiogram - records the heart’s electrical activity using electrodes

Question 7

How does the cardiac cycle look on an ECG

Answer 7

• Atrial systole is shown as a P wave
• Ventricular systole is shown as a QRS
• Diastole is shown as a T wave

Question 8

What abnormalities can an ECG show

Answer 8

• Tachycardia - abnormally rapid HR
• Bradycardia- abnormally slow HR
• Ectopic heartbeats - extra heartbeats out of the normal rhythm
• Atrial fibrillation- abnormally rapid and ineffective contraction of the atrial