1. The Structure and Function of the Heart
Higher Human Physiology and Health

2. What do you know now? What you are learning?
From your previous N5 or maybe S1/2 work label the diagram of the heart and write any facts you know.
What you are learning?
Revising the heart structure and function
The cardiac cycle and output
Cardiac conduction and heart beat
Cardiac pressures

3. superior vena cava
pulmonary veins
AV valve
mitral
AV valve
tricuspid
inferior vena cava

4. The Heart - external

5. The Heart - internal

6. Cardiac cycle

7. Systole / Diastole
Systole – when part of the heart is contracting either atria or ventricles
Diastole – when part of the heart is relaxing either atria or ventricles
Both atria contract or relax at the same time
Both ventricles contract or relax at the same time
Atria and ventricles can be relaxed at same time
Atrio-ventricular valves (AV) and semi-lunar valves (SL) are forced open or kept closed depending on systole or diastole of atria or ventricles
Valves allow flow of blood in one direction through the heart

8. Measuring cardiac output
Cardiac output = heart rate x stroke volume
CO HR SV
Cardiac output is the volume of blood pumped through each ventricle per minute
Heart rate is the number of times the heart beats per minute
Stroke volume is the volume of blood pumped through a ventricle at each beat
Each ventricle pumps the same volume of blood to aorta or pulmonary artery respectively

9. Cardiac output

10. Valves and heart sounds
Heart sounds come from the closing of valves and sounds like LUB/DUB
AV valve closes and gives the ‘LUB’ sound
SL valve closes and gives the ‘DUB’ sound
Heart murmurs can be heard and are defective valves

11. Heart sounds

12. Cardiac cycle

13. Cardiac cycle and pressure changes
Atria contract (systole) pushing blood into ventricle via AV valve, SL valve is closed
Ventricles contract (systole) closing the AV valve. Blood is pumped out into aorta or pulmonary artery via SL valve
All relax (diastole) SL valves closed

14. Cardiac conducting system
Heart beat originates in the heart
But it is regulated by nervous and hormonal control
Sinoatrial node
Atrioventricular node

15. Cardiac conducting system
Sinoatrial node (SAN) ii right atrium controls contractions and timing of beat
Impulses from SAN radiate across atria
Impulses from SAN transmitted to atrioventricular node (AVN) at base of atria
Conducting fibres pass down centrally and branch left and right across ventricles
Impulses sent to ventricular muscle fibres starting at apex (bottom) moving upwards
Atrial systole first then ventricular systole next (coordinated)

16. Measuring heart impulses
Impulses are electrical so can be
measured by electrocardiogram (ECG)
Electrodes placed on skin
3 distinct phases
P wave – atrial excitation from SAN
QRS complex – ventricle excitation
T wave – electrical recovery of ventricles

18. Abnormal ECGs
CPR
Defibrillator

19. Regulation and control of heart beat
Nervous
Control centre located in medulla
Autonomic nervous system
Cardio accelerator centre – sympathetic nerve increases heart rate
Cardio inhibitor centre – parasympathetic nerve decreases heart rate
Impulses sent to SAN
Relative number of impulses determines heart beat
Hormonal
Sympathetic nerve acts on adrenal gland
It releases norepinephrine (noradrenaline) speeding up heart rate
Parasympathetic nerve releases acetylcholine slowing heart rate

20. Measuring blood pressure
Blood pressure is the force put on walls of blood vessels
Measured in the aorta
Systolic pressure as left ventricle pushes blood out into aorta (pulse detected)
Diastolic pressure as left ventricular contraction has stopped (pulse not detected)
Measured in mm of mercury (Hg)
Typically 120 mm Hg for systolic
70 mm Hg for diastolic in young adult
(120 over 70)
Mercury manometer

21. Digital syphgmomanometer

23. Hypertension High blood pressure
Caused by many factors: being overweight, lack of exercise, diet of fatty foods, too much salt, excessive alcohol, high levels of stress
Measurements of 140 over 90 mm Hg for extended periods when resting
Hypertension increases risks of coronary heart disease and strokes

24. What you should know Know the heart structure and function
Know what cardiac output is how to calculate it
Know what the cardiac cycle is and describe it
Know how the cardiac cycle is controlled
Know how the cardiac cycle can be measured
Know what blood pressure is and how it can be measured
Consolidate your learning
Read appropriate pages from textbook,
complete questions in textbook, complete summary,
make own notes, complete scholar work