Edexcel iGCSE Biology-3.16 Heart Rate & Exercise- Study Notes- New Syllabus
Edexcel iGCSE Biology-3.16 Heart Rate & Exercise- Study Notes- New syllabus
Edexcel iGCSE Biology-3.16 Heart Rate & Exercise- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
3.16 explain how the heart rate changes during exercise and under the influence of adrenaline
Heart Rate: Exercise & Adrenaline
📝 Introduction
The heart rate is the number of times the heart beats per minute.
It changes depending on the body’s energy needs.
🏃♂️ Heart Rate During Exercise
- Muscles work harder → need more oxygen & glucose for aerobic respiration.
- Carbon dioxide levels in blood rise.
- Detected by receptors in the brain (medulla).
- Medulla sends nerve impulses to the heart → heart rate increases.
- This causes:
- Faster delivery of oxygen & glucose to muscles.
- Faster removal of CO₂ & lactic acid.
⚡ Heart Rate Under the Influence of Adrenaline
- Adrenaline = hormone released from adrenal glands (above kidneys) in “fight or flight” situations (stress, danger, excitement).
- Effects on heart:
- Increases heart rate.
- Increases stroke volume (amount of blood pumped per beat).
- Prepares body for rapid action (more oxygen & glucose to muscles).
📊 Summary Table
| Situation | Cause | Effect on Heart Rate | Why it Happens |
|---|---|---|---|
| Exercise | Increased CO₂ in blood | Heart rate ↑ | More O₂ & glucose delivered, CO₂ removed faster |
| Adrenaline | Stress, fear, excitement | Heart rate ↑ (stronger beats) | Prepares body for “fight or flight” |
⚡ Quick Recap
Exercise → brain detects more CO₂ → heart beats faster.
Adrenaline → directly stimulates heart → faster & stronger contractions.
Both ensure muscles get enough oxygen & glucose quickly.