1. THE CARDIAC CYCLE SYSTOLE : contraction DIASTOLE : relaxation
ATRIAL DIASTOLE
* begins when both atria and ventricles are relaxed
* blood enters atria
* atrio-ventricular valves are closed
* as atria fill with blood, the pressure rises until it is greater than that in the ventricles, and the valves are pushed open

3. ATRIAL SYSTOLE
* when atrial diastole ends, the atria contract, pumping blood into the ventricles
VENTRICULAR SYSTOLE
* the ventricles then contract, causing a rise in pressure
* the atrio-ventricular valves close - the first heart sound
* the pressure forces open the semi-lunar valves, and the blood flows out

4. VENTRICULAR DIASTOLE
* high pressure in the aorta and pulmonary artery forces blood back towards the ventricles, and this closes the semi-lunar valves : the second heart sound
NB the pulse is caused by ventricular systole, and the elastic recoil of the arteries

5. THE STRUCTURE OF THE HEART
Why are the walls of the atria thinner than the walls of the ventricles?
Why is the wall of the right ventricle thinner than the wall of the left ventricle?
What happens to the atrioventricular valves when the ventricles contract, and why?
4. What happens to the arterial valves when the ventricles relax, and why?
Which artery leaving the heart carries deoxygenated blood?
Which vein entering the heart carries oxygenated blood?

7. What is happening at 1, 2, 3 and 4?
Annotate the diagram in your workbook

10. THE CONTROL OF THE HEART BEAT
CARDIAC MUSCLE * branched
* myogenic
* does not fatigue

11. The Control of the Heartbeat
Cardiac muscle contracts rhythmically on its own, but different areas have different intrinsic rates.
The SINO-ATRIAL NODE (SAN) synchronizes the contraction of the different areas of cardiac muscle, so that the heart beats in a coordinated way.

13. The SAN sends out waves of excitation similar to nerve impulses across the surface of the atria, making them contract simultaneously.
When these impulses reach the ATRIO-VENTRICULAR NODE (AVN), they travel down special cardiac muscle fibres called PURKYNE TISSUE, which fan out across the ventricles. These impulses cause the ventricles to contract in a wave, starting from the bottom.

14. PURKYNE TISSUE

15. An ECG
This diagram shows the timing of the wave of excitation as it passes across the surface of the heart. An ELECTRO-CARDIOGRAM (ECG) shows this electrical activity.

16. The different phases of an ECG

18. Which of these is an artery, and which a vein?

19. TRANSVERSE SECTION THROUGH AN ARTERY
Connective
tissue
Smooth muscle
and elastic
tissue
LUMEN
Endothelium

20. Remember its all about structure and function
Small lumen – for high pressure
Smooth endothelium – Reduce friction, and corrugated to allow expansion
Elastic fibres – allow for stretch and recoil
Smooth muscle – Allow for constriction of the artery if needed
Collagen fibres – To with stand the high pressure

21. ARTERIES VEINS thick, muscular wall with thick layer of elastic fibres
thin wall with less muscle and elastic fibres
narrow lumen
wide lumen
generates pulse
no pulse
no valves*
valves
high pressure
low pressure
carry blood from the heart to organs
carry blood from organs to the heart
blood is usually+ oxygenated
blood is usually^ deoxygenated

22. * except the pulmonary artery, aorta,
^ except the pulmonary vein
and carotid arteries

23. Arteries divide up into smaller ARTERIOLES, which divide to form capillary networks.
Capillary networks drain into small veins called VENULES, which drain into large veins.

24. VALVES IN VEINS

25. As well as a potential cause of blood clots, varicose veins can cause ulcerations of the legs.

26. DEEP VEIN THROMBOSIS (DVT)
Blood clots that form in leg veins can dislodge and travel to other parts of the body, causing fatal problems such as heart attacks and pulmonary embolisms.

27. One cell think – allows for easy diffusion
Narrow lumen – allows only one blood cell down at a time, this slows the flow rate and allows time for diffusion

28. A CAPILLARY NETWORK – capillaries deliver food and oxygen to the tissues, at the same time removing carbon dioxide and other waste products. In order to do this efficiently, they are very narrow, with walls only one cell thick. This makes diffusion more efficient.

30. HOW DOES FLUID GET OUT OF THE CAPILLARY?
Through pores in the capillary wall.
WHICH COMPONENTS OF BLOOD WILL NOT PASS THROUGH THE PORES?
Blood cells and large blood proteins.

33. CALIBRATING AN EYEPIECE GRATICULE
Measure the size of the object using an eyepiece graticule.
Record the size in graticule units.
This is a stage micrometer:
Each large unit on the micrometer is 1mm.
Place this on the stage of the microscope with the graticule. Measure the actual length in mm of one graticule unit.
Convert the size of the object from graticule units to mm.