Topic 9.2B: Heart Function
The Beat, Exercise & Disease
Learning Objectives (Core & Supplement):
- • Describe the cardiac cycle and valve function
- • Explain why heart rate increases during exercise
- • Understand coronary heart disease causes and prevention
The Cardiac Cycle Animator
The heart beats in a repeating cycle of contraction and relaxation. Watch how the chambers and valves work together!
Atrial Contraction
Atria contract, pushing blood into ventricles
Examiner Trap:
Students often confuse "relaxation" with "no valve action." Remember: SL valves SHUT during relaxation to prevent backflow from the arteries!
Key Vocabulary (SUPPLEMENT)
Systole
Contraction phase of the heart
Diastole
Relaxation phase of the heart
Atrioventricular (AV) Valves
Valves between atria and ventricles
Semilunar (SL) Valves
Valves between ventricles and arteries
Learning Summary
Cardiac Cycle
Atria contract → AV valves open → Ventricles contract → SL valves open → Relaxation → SL valves shut
Exercise Effect
Muscles need O₂ + glucose for aerobic respiration → Heart rate increases to deliver more blood
CHD
Coronary arteries blocked → Heart muscle oxygen-starved → Heart attack. Prevent with diet & exercise.
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