1. THE FUNCTION OF CIRCULATION

2. IMPORTANT TERMS Pulmonary arteryleukocytes Pulmonary vein platelets Atrioventricular valvevasoconstriction Semilunar valvevasodilation Pulmonary circulation Systemic circulation Cardiac circulation Plasma Erythrocytes

3. Understanding Arteries convey blood at high pressure from the ventricles to the tissues of the body Arteries have muscles and elastic fibres in their walls The muscle and elastic fibres assist in maintaining blood pressure between pump cycles Blood flows through tissues in capillaries with permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart Valves in veins and the heart ensure circulation of blood by preventing backflow There is a separate circulation for the lungs

4. Understanding (continued) The heartbeat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node The sinoatrial node acts as a pacemaker The sinoatrial node sends out an electrical signal that stimulates contraction as it is propagated through the walls of the atria and then the walls of the ventricles The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain Epinephrine increases the heart rate to prepare for vigorous physical activity

5. Skills Identification of blood vessels as arteries, capillaries or veins from the structure of their walls Recognition of the chambers and valves of the heart and the blood vessels connected to it in dissected hearts or in diagrams of heart structure

6. Applications William Harvey’s discovery of the circulation of the blood with the heart acting as the pump Causes and consequences of occlusion of the coronary arteries Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle

7. MAIN FUNCTION The main function of the circulatory system is to deliver oxygen and nutrients to all the body’s cells Other important functions include:  Regulating internal temperature  Protects the body against invading microbes

8. COMPONENTS Main components of the circulatory system include :  The heart  Blood vessels (arteries and veins)  Blood

9. THE HEART Your heart is tucked in behind your left lung slightly to the left of your sternum (central rib bone) Humans have a four chambered heart that includes the: Right atrium Left atrium Right ventricle Left ventricle

10. THE HEART The atria are small chambers at the top of the heart. They receive blood from veins The ventricles are larger chambers at the bottom of the heart. They pump blood out

11. THE CARDIAC CYCLE Blood takes a very specific path through the body and this path repeats over and over again. It is called the cardiac cycle It starts at the right atrium.

12. THE RIGHT ATRIUM Blood from here has just come from the body. Oxygen has been removed from this blood and it contains CO2 It is dark maroon blue colour Blood gets pumped from here through a valve called the tricuspid valve into the right ventricle

13. RIGHT VENTRICLE Blood here is still deoxygenated (has no oxygen). It gets pumped out of the heart into the pulmonary artery. It then travels to the lungs to pick up oxygen

14. LEFT ATRIUM Blood has just returned from the lungs where it has picked up oxygen It is fully oxygenated and has a bright red colour It is pumped through the bicuspid valve into the left ventricle

15. LEFT VENTRICLE This is the strongest, most muscular chamber of the heart Blood from here is pumped out of the heart into the aorta where it will travel throughout the body. As the blood travels through the body it drops of oxygen and nutrients at all the cells

16. Heart Diagram

18. CARDIAC CYCLE

19. Controlling the Heart The heart is a unique organ. It is mostly made of muscle cells. While other muscles are contracted because of impulses from nerves, the heart has the ability to contract itself without the help of nerves In fact, hearts can continue to pump for a while even after they have been removed from the body. This property is known as myogenic pacemaker potential

20. The Sinoatrial Node The Sinoatrial, or SA, node is the place in the heart where contraction is initiated. It is located at the top of the right atrium and consists of specialized muscle cells. It is able to change the concentration of certain ions in the cells which causes contraction to occur When it contracts, adjacent cells will contract as well.

21. The Atrioventricular Node The signal from the SA node spreads quickly throughout the ventricles It reaches another centre for specialized cells, the atrioventricular, or AV node. The AV node transmits the electrical signal to the ventricles after a slight delay so the ventricles can fill with blood

22. Bundle of His/Bundle Branches/Purkinje Fibers From the AV node, the signal travels down through more specialized muscle cells including the bundle of His and bundle branches that are located in the septum between the ventricles. The signal travels down to the bottom of the ventricles and contraction starts there and works its way up both sides of the ventricles (purkinje fibers). This leads to a more efficient heart beat

23. Controlling the Heart Rate The SA node sets the initial heart rate It varies from person to person but is usually between 60 and 100 beats per minute The pressure and content of the blood is constantly monitored by special receptors; baroreceptors monitor pressure and chemoreceptors monitor levels of oxygen, CO2 and other substances

24. Controlling the Heart https://www.youtube.com/watch?v=RYZ4daFwMa8

25. Control of the Heart These receptors are connected to nerves that can cause the heart to speed up or slow down depending on the need. The following are all indicators that the heart needs to speed up  Low oxygen levels  Low pH  Low blood pressure  Conversely, the opposite readings will signal the heart to slow down.

26. Nerves That Affect Heart Rate The autonomic nervous system (the part of the nervous system that we can’t control) is divided into two parts:  The sympathetic system &  The parasympathetic system Generally speaking, the sympathetic system increases metabolism while the parasympathetic system slows it down.

27. Nerves Affecting the Heart The heart has two major nerves connected to it: 1. The acclerator nerve (sympathetic speeds it up) 2. The vagus nerve (parasympathetic slows it down)

28. Hormones Hormones are chemical messengers that are released into the blood and affect a target organ. Some hormones target the heart Most notably, epinephrine and norepinephrine (also called adrenaline and noradrenaline) are released from the adrenal glands during times of stress and cause the heart rate to increase

29. The Cardiac Cycle Go through the phases of the cardiac cycle described on page 300. Compare the time intervals to the chart below https://www.youtube.com/watch?v=jLTdgrhpDCg

30. Cardiac Cycle Confusing but important!!!

31. BLOOD VESSELS Blood vessels take blood throughout the body. If your body were a city, blood vessels would be the roads and highways There are two types of blood vessels; arteries and veins

32. ARTERIES VIENS Carries blood away from the heart Thicker and more muscular More elastic Brings blood back to the heart Thinner Less elastic, more compliant (stretchy) Have valves that keep blood moving in the right direction BLOOD VESSELS

33. ARTERIES VEINS BLOOD VESSELS

34. MORE TYPES OF BLOOD VESSELS Blood leaves the heart through large arteries (aorta and pulmonary) Large arteries branch off to smaller arteries Smaller arteries branch into smaller arterioles Arterioles continue to branch until they form tiny vessels called capillaries Blood flows through capillaries which merge together to form venules Venules merge to form veins Veins come together to form larger veins (vena cava and pulmonary vein) which deliver blood back to the heart

35. BLOOD VESSELS

37. BLOOD If you take a test tube of blood and spin it in a centrifuge it will quickly divide into two parts. They are:  Cells and  Plasma

38. HEMATOCRIT PLASMA Approximately 45% of your blood Contains mostly red blood cells or erythrocytes and some white blood cells or leukocytes Approximately 55% of your blood Contains mostly water but also has dissolved gases, proteins, salts and other nutrients BLOOD

39. RED CELLS (ERYTHROCYTES) WHITE CELLS (LEUKOCYTES) Shaped like a donuts without a hole Make up over 99% of blood cells Made in bone marrow Contain hemoglobin which carries oxygen Different shapes Make up less than 1% of blood cells Purpose is to attack foreign microbes Two main types:  Granulocytes – engulf invaders  Agranulocytes – involved in the formation of antibodies TYPES OF BLOOD CELLS

40. RED WHITE TYPE OF BLOOD CELLS

41. PLATELETS Prevent excessive blood loss by causing blood to clot or coagulate  Broken blood vessels release chemicals that attract platelets  Platelets rupture which releases substances which react with certain plasma proteins to form thromboplastin which gets converted to thrombin (an enzyme)  Thrombin converts fibrinogen (a plasma protein) to fibrin  Fibrin forms a mesh like substance (a scab) that stops blood from escaping

42. BLOOD CLOTTING

43. CONTROL OF BLOOD FLOW One of the really amazing things about the circulatory system is that it has the ability to control where the blood goes. Remember, arteries have a layer of muscle cells called smooth muscle. Smooth muscle is not a voluntary muscle. It is controlled by the brain. When it contracts, called vasoconstriction, the arteries narrow and decrease the blood supply. When smooth muscle relaxes, it is called vasodilation. This makes the artery wider and increases the amount of blood that flows through it

44. CONTROL OF BLOOD FLOW Blood flow is controlled for two main reasons: 1. To allow more active parts of the body to receive more blood than inactive parts. 2. To maintain body temperature in the most important parts of the body