1. Option D.4 The Heart

2. Understandings
D.4.U1: Structure of cardiac muscle cells allows propagation of stimuli through the heart wall.
D.4.U2: Signals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles.
D.4.U3: There is a delay between the arrival and passing on of a stimulus at the atrioventricular node.
D.4.U4: This delay allows time for atrial systole before the atrioventricular valves close.
D.4.U5: Normal heart sounds are caused by the atrioventricular valves and semilunar valves closing causing changes in blood flow.
D.4.U6: Conducting fibres ensure coordinated contraction of the entire ventricle wall.
D.4.A1: Use of artificial pacemakers to regulate the heart rate.
D.4.A2: Use of defibrillation to treat life-threatening cardiac conditions.
D.4.A3: Causes and consequences of hypertension and thrombosis.
D.4.S1: Measurement and interpretation of the heart rate under different conditions.
D.4.S2: Interpretation of systolic and diastolic blood pressure measurements.
D.4.S3: Mapping of the cardiac cycle to a normal ECG trace.
D.4.S4: Analysis of epidemiological data relating to the incidence of 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.

3. 6.2.1 – Be able to draw and label a human heart
Right
atrium
Left
atrium
Semilunar
valve
Semilunar
valve
Atrioventricular
(AV) valve
Atrioventricular
(AV) valve
Right
ventricle
Left
ventricle

4. 6.2.2 The heart is supplied with nutrients / oxygen
from coronary arteries:
The heart is made of muscle cells which need fuel

5. 6.2.3 Heart blood flow The heart collects blood in the atrium(s)
Valves open and close sequentially to maintain a ‘one way’ flow
Valves are divided
into two or three sections

6. D.4.U1: Structure of cardiac muscle cells allows propagation of stimuli through the heart wall.
Cardiac muscles are linked by intercalating discs and are also branched
These connections allow for increased blood flow and ability contract simultaneously
Skeletal muscle

8. The SAN receives signals from medulla oblongata (or epinephrine)
D.4.U2: Signals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles. D.4.U3: There is a delay between the arrival and passing on of a stimulus at the atrioventricular node.
The SAN receives signals from medulla oblongata (or epinephrine)
These cells cause atrial
systole(contraction) and
stimulation of AVN
AVN sends signal from
atrium, down center of
the heart and causes
ventricular systole

10. D.4.U4: This delay allows time for atrial systole before the atrioventricular valves close. D.4.U5: Normal heart sounds are caused by the atrioventricular valves and semilunar valves closing causing changes in blood flow.
Important to make sure atrial valves are closed when ventricular valves are open and vice versa

11. D.4.U6: Conducting fibers ensure coordinated contraction of the entire ventricle wall.
The signal travels from SAN to AVN to fibers which contract the ventricles

12. D.4.A1: Use of artificial pacemakers to regulate the heart rate.
Problems with signal conduction (too fast or to slow) can be regulated by a pacemaker
Also used after heart attacks if heart rate is not coordinated properly

13. D.4.A2: Use of defibrillation to treat life-threatening cardiac conditions.
Used to restart or correct a heart that is not beating sufficiently
Delivers an electronic pulse between two electrodes

14. D.4.A3: Causes and consequences of hypertension and thrombosis.
Thrombosis is the formation of a blood clot in blood vessels. Causes blockage, may break free and travel to other areas
Caused by being
overweight or immobility
among other things

15. D.4.A3: Causes and consequences of hypertension and thrombosis.
Hypertension is high blood pressure caused by narrower blood vessels, which makes the heart work harder
Can lead to heart attacks
Caused by: stress,
overweight alcohol,
dietary

16. D.4.S1: Measurement and interpretation of the heart rate under different conditions.

17. D.4.S2: Interpretation of systolic and diastolic blood pressure measurements.
Systolic pressure is the pressure created by each contraction of the heart, diastolic is the lower pressure during relaxation

18. D.4.S3: Mapping of the cardiac cycle to a normal ECG trace.
P wave represents the atrial contraction (systole)
QRS wave represents ventricular
contraction
The T wave represents
ventricular relaxation (diastole)
Can show signs of a heart attack

19. Heart Sounds are caused by the opening and closing of valves, not by muscles contracting

20. D.4.S4: Analysis of epidemiological data relating to the incidence of coronary heart disease.
What causes differences in coronary hear deaths? Diet, lifestyle, genotype…