OrganisationDeep Dive
The Cardiac Cycle: How Your Heart Beats
Part of The Heart and Circulation — GCSE Biology
This deep dive covers The Cardiac Cycle: How Your Heart Beats within The Heart and Circulation for GCSE Biology. Heart structure, cardiac cycle, blood vessels, double circulation, heart rate control, and cardiovascular health It is section 4 of 14 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 4 of 14
Practice
20 questions
Recall
25 flashcards
The Cardiac Cycle: How Your Heart Beats
1. Atrial Systole (0.1 seconds)
- Both atria contract simultaneously
- AV valves (tricuspid and bicuspid) are open
- Blood pushed from atria to ventricles
- Ventricles fill completely (end-diastolic volume)
- Semi-lunar valves (pulmonary and aortic) remain closed
2. Ventricular Systole (0.3 seconds)
- Both ventricles contract with massive force
- AV valves snap shut → first heart sound "LUB"
- Pressure builds in ventricles
- Semi-lunar valves forced open
- Blood ejected into aorta and pulmonary artery
- This creates your pulse and blood pressure
3. Complete Diastole (0.4 seconds)
- All chambers relax
- Semi-lunar valves snap shut → second heart sound "DUB"
- AV valves open as pressure drops
- Blood flows passively from atria to ventricles
- Coronary arteries fill with blood (heart muscle fed)
- Cycle ready to repeat
Cardiac Output Calculation
Cardiac Output = Heart Rate × Stroke Volume
Example: Resting adult
- Heart Rate = 70 beats per minute
- Stroke Volume = 70 ml per beat
- Cardiac Output = 70 × 70 = 4,900 ml/min ≈ 5 litres/min
During Exercise:
- Heart Rate can increase to 180+ bpm
- Stroke Volume can increase to 120+ ml
- Cardiac Output can reach 20+ litres/min