Heart And Cardiac Cycle

Question 1

Atrial Systole

Answer 1

• Blood enters atria from superior vena cava and pulmonary vein
• Atria contract (systole)
• Volume of atria decreases and atrial pressure increases
• Atrioventricular valves forced open as pressure in atrium higher than in ventricle
• Blood enters ventricles through valves down pressure gradient

Question 2

Ventricular systole

Answer 2

• Ventricles contract (systole)
• Volume in ventricles decreases and ventricular pressure increases
• AV valves close by rise in ventricular pressure
• Prevents backflow of blood into atria
• Semi-lunar valves open as pressure in ventricles greater than arteries
• Blood forced through SL valves into aorta and pulmonary artery out of heart

Question 3

Diastole

Answer 3

• Ventricles relax
• Higher volume and lower pressure so SL valves cusps closed
• Pressure greater in pulmonary artery/ aorta so prevents backflow of blood

Question 4

What creates the lub-dub sound of the heartbeat?

Answer 4

AV (lub) and SL (dub) valves closing

Question 5

Prevent backflow of blood in heart

Answer 5

• Atrio-ventricular valves close to prevent backflow
• When pressure in the ventricle exceeds the pressure in atria during systole
• Tendons prevent valves inverting (chordae tendineae)

Question 6

Why bicuspid/ left AV/ mitral valve needs to be replaced

Answer 6

• Exposed to a higher pressure in the left ventricle
• Tricuspid valve exposed to lower pressure to lungs as right ventricle pumps blood at lower pressures
• Damaged = blood flow/ leaks back from ventricle to atrium
• Breathlessness and fatigue

Question 7

Coronary arteries

Answer 7

Provide oxygen and glucose to the heart/ cardiac muscle

If narrowed, O2 does not reach heart muscles = unable to respire

Question 8

Why more blood through coronary arteries during exercise?

Answer 8

• Increased oxygen and glucose/ nutrients provided for aerobic respiration
• Removal of CO2 and lactic acid