1. Use of artificial pacemakers to regulate the heart rate
D.4 The Heart
Understanding:
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 flor
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
Nature of science:
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
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

2. Atrioventricular valves
Review Topic 6
Aorta
Pulmonary vein
Pulmonary artery
Vena cava
Left atrium
Right atrium
Left ventricle
Right ventricle
Semi lunar valves
Atrioventricular valves
Septum

3. Atrioventricular valves
Review Topic 6
Semi lunar valves
(Arteries)
Atrioventricular valves
(Atria/Ventricles)
Right
Left

5. Systole and Diastole of ventricles and atria
Pressure changes
Aorta (black)
Left atrium (Blue)
Left ventricle (red)
Systole and Diastole of ventricles and atria
Heart Sounds
Valves opening and closing
(Aortic valve = semilunar valve)

6. Pressure decreasing during atrial and ventricular diastole.
Aorta
Pressure decreasing during atrial and ventricular diastole.
Semi lunar valve is closed
Blood has left the ventricle and the heart relaxes

7. Atrial systole begins followed by ventricular systole
Aorta
Atrial systole begins followed by ventricular systole
Immediately the semi lunar valve opens
Pressure increases rapidly as blood enters the Aorta
Pressure reaches a maximum point
At the end of ventricular systole the semilunar valve closes and pressure in Aorta decreases

8. Pressure is low during atrial and ventricular diastole
Atrium and Ventricle
Pressure is low during atrial and ventricular diastole
Heart is relaxed
Atrioventricular valve is open
Blood starts to fill atrium and moves into ventricle

9. Pressure increases in both atrium and ventricle as blood fills
Atrium contracts to push blood into ventricle
Atrioventricular valve closes and pressure in atrium decreases

10. Rapid increase in pressure in ventricle as it contracts
Atrium and Ventricle
Rapid increase in pressure in ventricle as it contracts
As the pressure rises, the semilunar valve opens
Pressure has reached a maximum and blood is pumped out of ventricle and into aorta

11. Semilunar valve closes and pressure in ventricle decreases rapidly
Atrium and Ventricle
Semilunar valve closes and pressure in ventricle decreases rapidly
Blood slowly fills atrium
Atrioventricular valve opens and blood continues to fill the atrium and now the ventricle
Atrium contracts and the cycle starts again

12. No nerve impulses needed
Review Topic 6
The heart is myogenic
Sinoatrial node (right atrium wall) initiates and sets pace for heart beat
No nerve impulses needed
Atrial systole
Ventricular systole
Diastole

13. SA node Uniquely structured cardiac cells
Initiate action potential without stimulation by other nerves
Contractions spread rapidly across atrium
Stimulate atrial systole
Understanding:
Signals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles

14. Cardiac muscle is unique
Striated appearance
Understanding:
Structure of cardiac muscle cells allows propagation of stimuli through the heart wall

15. Cardiac Muscle Cells
Joined end to end in a complex network of interconnected cells
Gaps called intercalated discs
Provide channels of connected cytoplasm between cells
Allows rapid movement of ions
Very fast wave of depolarization
Understanding:
Structure of cardiac muscle cells allows propagation of stimuli through the heart wall

17. Cardiac Cycle
Fibres in atrial walls prevent impulses moving to ventricles
Signals pass from SA node to atrioventricular node.
Understanding:
Signals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles

18. Cardiac Cycle Passes down Bundle of His
Moves down left and right bundle branches to the apex of the heart
Down to the Purkinje fibres
Causes the ventricles to contract at apex
Cardiac Cycle
Understanding:
Signals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles

19. Purkinje Fibres Able to conduct signal at high speed
Large diameter of cells
Many Na+ channels
Many mitochondria
Understanding:
Signals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles
Conducting fibres ensure coordinated contraction of the entire ventricle wall

20. Cardiac Cycle Delay needed between nodes
Ensures staggering of contractions
Atria empty first before ventricles contract
AV node has many features delaying the contractions of the ventricles
Understanding:
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

21. AV node Smaller cell diameter Reduced number of Na+ channels
Fewer gap junctions between cells
Slower conduction overall compared to SA node
Understanding:
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

22. ECG machine ELECTROCARDIOGRAM
Use the ECG machine to detect the electrical signals in your heart
P wave: Atrial systole
QRS complex: Ventricular systole
T wave: Ventricular diastole
Doctors use this to see if your heart pattern is normal
Able to detect fibrillations
Skills:
Mapping of the cardiac cycle to a normal ECG trace

24. Hypertension and thrombosis
Revisit atherosclerosis – what is it?
Then answer the following questions
What is thrombosis?
What is hypertension?
What causes each of these?
What are the consequences?
How do the factors on the right affect thrombosis and/or hypertension?
Height
Genetics
Age
Gender
Smoking
Diet
Exercise
Applications:
Causes and consequences of hypertension and thrombosis

25. Atrioventricular valves closing = lub Semilunar valves closing = dub
Caused by valves snapping shut
Atrioventricular valves closing = lub
Semilunar valves closing = dub
Stethoscopes invented in 19th century
Doctors used to place ears on patients chest before
Difficulty with female or obese patients
Now a lot easier and non invasive
Heart Beat
Understanding:
Normal heart sounds are caused by the atrioventricular valves and semilunar valves closing causing changes in blood flor
Nature of science:
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

26. Defibrillator No/reduced blood supply to the heart Cardiac arrest
Heart tissues deprived of oxygen
Causes ventricular fibrillation = twitching of muscle cells in ventricles
Defibrillators detect if this is happening
Then used to restore rhythm to the heart
Paddles must be placed diagonally across the heart
Applications:
Use of defibrillation to treat life-threatening cardiac conditions

27. ECG machine ELECTROCARDIOGRAM
Use the ECG machine to measure your heart rate under the following different conditions
Exercise
Relaxation
Lying down
Holding your breathe
Fast breathing
Facial immersion in water (OPTIONAL!!)
Skills:
Measurement and interpretation of the heart rate under different conditions

28. Blood Pressure Measuring blood pressure
Pressure on artery walls by circulating blood
Higher number = ventricular systole pressure
Lower number = ventricular diastole pressure
Many different blood pressure machines
Take your blood pressure!
Skills:
Interpretation of systolic and diastolic blood pressure measurements