Topic D.4: The Heart

Essential Idea:  Internal and external factors influence heart function.
At SHS, Topic D.4 is taught in the following class unit(s):

Statements & Objectives:

D.4.U1  Structure of cardiac muscle cells allows propagation of stimuli through the heart wall.
  • Compare cardiac muscle tissue to skeletal muscle tissue.
  • Contrast cardiac muscle tissue to skeletal muscle tissue.
  • Describe how the Y-shape, intercalated discs and gap junctions of cardiac muscle cells allow for propagation of the stimulus to contract.
D.4.U2  Signals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles.
  • Explain the events of the cardiac cycle, including atrial and ventricular systole and diastole and the movement of the signal to contract through the heart.
  • Outline the role of the atrioventricular node in the cardiac cycle.​
D.4.U3  There is a delay between the arrival and passing on of a stimulus at the atrioventricular node.
  • Outline the causes of the delayed initiation of contraction of ventricles. 
D.4.U4  This delay allows time for atrial systole before the atrioventricular valves close.
  • State the function of a delayed contraction of the ventricle.
D.4.U5  Conducting fibres ensure coordinated contraction of the entire ventricle wall.
  • Describe the motion of the signal to contract from the AV node through the ventricles.
  • List features of Purkinje fibers that facilitate rapid conduction of the contraction signal through the ventricle.
  • State that the contraction of the ventricle begins at the heart apex.
D.4.U6  Normal heart sounds are caused by the atrioventricular valves and semilunar valves closing causing changes in blood flow.
  • State the cause of each of the two sounds of the heartbeat.
D.4.A1  Use of artificial pacemakers to regulate the heart rate.
  • State the purpose of an artificial pacemaker device.
D.4.A2  Use of defibrillation to treat life-threatening cardiac conditions.
  • State the cause and effect of ventricular fibrillation.
  • State the purpose of a defibrillator.
D.4.A3  Causes and consequences of hypertension and thrombosis.
  • Describe the relationship between atherosclerosis and thrombosis.
  • Describe the relationship between atherosclerosis and hypertension.
  • List consequences of hypertension.
  • Outline factors that are correlated with a greater incidence of thrombosis and hypertension.
D.4.S1  Measurement and interpretation of the heart rate under different conditions.
  • List variables that can influence heart rate.
  • Outline methods for detecting heart rate.
D.4.S2  Interpretation of systolic and diastolic blood pressure measurements.
  • State the cause of systolic and diastolic pressure.
  • Describe how sound is used to measure blood pressure.​
D.4.S3  Mapping of the cardiac cycle to a normal ECG trace.
  • State the function of an electrocardiogram.
  • Label the P, Q, R, S and T waves on an ECG trace.
  • State the cause of the P wave, the QRS wave and the T wave.
  • State an application of the use of ECG technology.
D.4.S4  Analysis of epidemiological data relating to the incidence of coronary heart disease.
  • Define epidemiology.
  • List epidemiological factors that can predispose ethnic groups to coronary heart disease.
D.4.NOS:  Developments in scientific research followed improvements in apparatus or instrumentation—the invention of the stethoscope led to improved knowledge of the workings of the heart.
  • List variables that lead to the development of the stethoscope.
  • State the function of the stethoscope.
"When we try to pick out anything by itself, we find it hitched to everything else in the Universe." 
 John Muir,   1911