Essential Idea:
Internal and external factors
influence heart function
Understandings:
- Structure of cardiac muscle cells allows propagation of stimuli through the heart wall
- Signals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles
- There is a delay between the arrival and passing on of a stimulus at the atrioventricular node
- This delay allows time for atrial systole before the atrioventricular valves close
- Conducting fibres ensure coordinated contraction of the entire ventricle wall
- Normal heart sounds are caused by the atrioventricular valves and semilunar valves closing causing changes in blood flow
Applications:
- Use of artificial pacemakers to regulate the heart rate
- Use of defibrillation to treat life-threatening cardiac conditions
- Causes and consequences of hypertension and thrombosis
Skills:
- Measurement and interpretation of the heart rate under different conditions
- Interpretation of systolic and diastolic blood pressure measurements
- Mapping of the cardiac cycle to a normal ECG trace
- Analysis of epidemiological data relating to the incidence of coronary heart disease