D4. The Heart

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 and skills:

Application: Use of artificial pacemakers to regulate the heart rate.

Application: Use of defibrillation to treat life-threatening cardiac conditions.

Application: Causes and consequences of hypertension and thrombosis

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Skill: Measurement and interpretation of the heart rate under different conditions.

Skill: Interpretation of systolic and diastolic blood pressure measurements.

Skill: Mapping of the cardiac cycle to a normal ECG trace.

Skill: Analysis of epidemiological data relating to the incidence of coronary heart disease.