1. 6.2 The Blood System
Essential idea: The blood system continuously transports substances to cells and simultaneously collects waste products.

2. Understandings Statement Guidance 6.2 U.1
Arteries convey blood at high pressure from the ventricles to the tissues of the body
6.2 U.2
Arteries have muscle cells and elastic fibers in their walls
6.2 U.3
The muscle and elastic fibers assist in maintaining blood pressure between pump cycles
6.2 U.4
Blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary
6.2 U.5
Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart.
6.2 U.6
Valves in veins and the heart ensure circulation of blood by preventing backflow.
6.2 U.7
There is a separate circulation for the lungs.
6.2 U.8
The heart beat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node
6.2 U.9
The sinoatrial node acts as a pacemaker.
6.2 U.10
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
6.2 U.11
The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.
6.2 U.12
Epinephrine increases the heart rate to prepare for vigorous physical activity

3. Applications and Skills
Statement
Guidance
6.2 A.1
William Harvey’s discovery of the circulation of the blood with the heart acting as the pump.
6.2 A.2
Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle.
6.2 A.3
Causes and consequences of occlusion of the coronary arteries.
6.2 S.1
Identification of blood vessels as arteries, capillaries or veins from the structure of their walls.
6.2 S.2
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.

5. What are the issues when organizes become multicellular?
Diffusion is not adequate for moving material across more than 1 cell barrier

6. Circulatory system solves this problem
carries fluids & dissolved material throughout body
cells are never far from body fluid
only a few cells away from blood
overcoming the limitations of diffusion

8. There are three main types of blood vessel:
Arteries carry high pressure blood away from the heart to tissues that need it
Capillaries are very small (< 10 μm diameter) and therefore can penetrate virtually every tissue in the body. Blood moves slowly through them under low pressure providing opportunities for the exchange of substances.
Veins carry the low pressure blood back to the heart using valves to ensure blood flows in the correct direction.

9. The structure of arteries
6.2 U.1 Arteries convey blood at high pressure from the ventricles to the tissues of the body. AND 6.2 U.2 Arteries have muscle cells and elastic fibers in their walls. AND 6.2 U.3 The muscle and elastic fibers assist in maintaining blood pressure between pump cycles
Thick muscular wall and fibrous outer layer help the artery to withstand high pressure
Relatively (to the wall) small lumen maintains high blood pressure.
Muscle contracts to decrease the size of the lumen. This causes an increase blood pressure and therefore maintains high blood pressure between the pulses of high pressure blood travelling from the heart
Elastic fibers stretch to increase the lumen with each pulse of blood. After the pulse of blood passes the fibers recoil decreasing the lumen size and therefore helping to maintain a high blood pressure.
The structure of arteries .

10. 6.2 U.5 Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart. AND 6.2 U.6 Valves in veins and the heart ensure circulation of blood by preventing backflow.
The structure of veins
Veins return blood to the heart for re-circulation.
The large lumen (compared to arteries and the thickness of the wall) means that the blood is under low pressure.
Because there is less pressure to resist the walls of the veins are thinner and less elastic than arteries. They also contain less muscle than the arteries.
Because of the low pressure valves are required to prevent back-flow of the blood and therefore ensure that the blood moves towards to heart.

11. 6.2.U5 Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart. AND 6.2.U6 Valves in veins and the heart ensure circulation of blood by preventing backflow.
Veins carry blood back to the heart. Have thin walls containing valves to prevent the back flow of blood, due to the lower pressure of blood in the veins.
Pressure in veins is low, so veins depend on nearby muscular contractions to move blood along.

12. The structure of capillaries
6.2 U.4 Blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary.
The structure of capillaries
Capillaries are the smallest blood vessels and are adapted for the exchange of substances to and from the blood.
This enables tissues to gain nutrients and molecules such as oxygen and to rid themselves of waste material.
Capillaries also allow substances to enter and leave the organism, e.g. gas exchange of oxygen and carbon dioxide in the lungs.
Due the the massive number of capillaries present and the small lumen the surface area available for the exchange of substances is very large.

13. 6.2 S.1 Identification of blood vessels as arteries, capillaries or veins from the structure of their walls.
Identify the labelled structures using your understanding of blood vessels. a d c b

14. 6.2 S.1 Identification of blood vessels as arteries, capillaries or veins from the structure of their walls.
Identify the labelled structures using your understanding of blood vessels.

15. Theories of blood movement around the body
Nature of Science: Theories are regarded as uncertain - William Harvey overturned theories developed by the ancient Greek philosopher Galen on movement of blood in the body. (1.9)
Remember a theories are by definition the best accepted explanations and predictions of natural phenomena. Although they are usually thoroughly tested based on evidence and reason theories theories are the only the current best accepted explanation. Theories if successfully questioned can be modified or even rejected/falsified if a better explanation arises.
Theories of blood movement around the body
Galen (129 - c216) Blood was not seen to circulate but rather to slowly ebb and flow. Using elusive attractive powers.
Ibn-al-Nafiz (1300) first challenger to Galen idea of blood movement
William Harvey ( ) published “De Motu Cordis” in Even then it took many years for his theory of systemic circulation (similar to modern accepted theory) to succeed Galen’s.

16. 6.2 U.7 There is a separate circulation for the lungs.
Path of blood through the heart
Deoxygenated blood return to the heart to right atrium from the body
The Right Atrium, receives "used blood" from the body. Blood will be pushed through the tricuspid valve to the
Right Ventricle, the chamber which will pump to the lungs through the pulmonic valve to the
Pulmonary Arteries, providing blood to both lungs. Blood is circulated through the lungs where carbon dioxide is removed and oxygen added. It returns through the Systemic Circuit.

17. 6.2 U.7 There is a separate circulation for the lungs.
Path of blood through the heart
Oxygenated blood enters the Left Atrium from the lungs
Pulmonary Veins, empty into the Left Atrium.
From the Left Atrium, a chamber which will push the Mitral Valve open. Blood then passes into the
Left Ventricle. Although it doesn't always look like it in drawings done from this angle, this is the largest and most important chamber in the heart. It pumps to the rest of the body. As it pumps, the pressure will close the mitral valve and open the aortic valve, with blood passing through to the Pulmonary Circuit

18. 6.2.S.2 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
Part of the Heart
a. Atria: thin-walled upper chambers which collect blood returning to the heart
b. Ventricles: thick, muscular lower chambers which pump blood to the lungs and other body tissue.
c. Septum (wall): separate the right and left sides of heart to prevent mixing of oxygenated and deoxygenated blood.

19. 4. Bicuspid valve / AV valve
6.2.S2 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
Valves of the Heart
1. Tricuspid valve /AV valve
4. Bicuspid valve / AV valve
2. Pulmonary valve
3. Aortic valve

20. Label the heart diagram
6.2 S2 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.
Label the heart diagram

21. Label the heart diagram
6.2.S2 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.
Label the heart diagram
bicuspid valve
Now try to label this heart:

23. When you take your pulse, you feel (or hear) two changes in pressure.
6.2 U.8 The heart beat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node.
6.2 U.9 The sinoatrial node acts as a pacemaker.
6.2 U.10 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.
Pulse
When you take your pulse, you feel (or hear) two changes in pressure.
The first sound is the closing of the AV’s (systolic pressure), the “lub” sound the heart makes. The 2nd sound is the closing of the SV’s (diastolic pressure), the “dub” sound.

24. Control of the Heart Beat
6.2 U.8 The heart beat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node.
6.2 U.9 The sinoatrial node acts as a pacemaker.
6.2 U.10 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.
Control of the Heart Beat
Beating is due to myogenic muscle. Meaning it is the origin of contraction in the heart and is not controlled externally
The hearts pacemaker (Sinoatrial Node/SA node) which controls the rate of heartbeats is made up of this muscle.
Large groups of these cell cause the atria to contract.
The contraction cause a signal to a group of nerve cells causing the ventricles to contract at the atrioventricular node/AV node.

25. The control of heart rhythm
6.2 U.8 The heart beat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node.
6.2 U.9 The sinoatrial node acts as a pacemaker.
6.2 U.10 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 control of heart rhythm

26. 6.2 U.8 The heart beat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node.
6.2 U.9 The sinoatrial node acts as a pacemaker.
6.2 U.10 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 interrelationship of blood flow velocity, cross-sectional area of blood vessels, and blood pressure

27. Control of the Heart Beat
6.2 U.11 The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.
6.2 U.12 Epinephrine increases the heart rate to prepare for vigorous physical activity.
Control of the Heart Beat
Controlled by the autonomic nervous system response to changing body conditions by speeding up or lowing down breathing
When the level of CO2 are low chemical receptors in the Medulla sends a signal to the Vagus nerve which decreases heart rate.
When the level of CO2 high chemical receptors in the Medulla sends a signal to the Accelerator nerve which increase heart rate.
SA Node
Medulla
Accelerator Nerve
Vagus Nerve

28. 6.2 U.11 The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.
6.2 U.12 Epinephrine increases the heart rate to prepare for vigorous physical activity.
Hormonal Control of Heart Rate
Epinephrine, more commonly known as adrenaline, is a hormone secreted by the medulla of the adrenal glands
Released into the bloodstream, epinephrine causes an increase in heart rate, muscle strength, blood pressure, and sugar metabolism.

29. How does the Heart work? STEP ONE The heart beat begins when the
blood from the body
blood from the lungs
The heart beat begins when the
heart muscles relax and blood
flows into the atria.

30. How does the Heart work? The atria then contract and
STEP TWO
The atria then contract and
the valves open to allow blood
into the ventricles.

31. The cycle then repeats itself.
How does the Heart work?
STEP THREE
The valves close to stop blood
flowing backwards.
The ventricles contract forcing
the blood to the aorta and out of the
heart.
At the same time, the atria are
relaxing and once again filling with
blood.
The cycle then repeats itself.

32. 6.2 A.2 Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle.
Right Atria & Ventricles relax and blood flows into the heart from the veins.
AV valve open, Right Atria contacts and Ventricle relaxes, blood moves into the ventricle.
Pulmonary valve opens, Right Ventricle contracts, blood flows to the lungs.
Blood flows from the lung into the left Atria AV valve opens, blood flows into the Left Ventricle.
Left Atria contracts blood flows into Left Ventricle.
Aortic valve opens, Left Ventricle contracts blood flows into the arteries.

33. The Cardiac Cycle Ventricular Pressure
6.2 A.2 Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle.
The Cardiac Cycle
Ventricular Pressure
Ventricular pressure increases as ventricle contracts. This forces blood into the aorta, increasing aortic pressure.
(a) Shows the increase in atrial pressure due to atrial contraction.
Shows increase in atrial pressure due to the inflow of blood from the veins (following systole).
Ventricular Volume
Increase as atrial contraction forces blood into the ventricle
Decrease as ventricular contraction forces blood into the aorta
Increases as blood returns to the heart following systole.
Click on the hyperlink

34. Coronary arteries supply heart muscles with oxygen and nutrients
6.2 A3 Causes and consequences of occlusion of the coronary arteries.
6.3 A1 Causes and consequences of blood clot formation in coronary
Arteriosclerosis 
Hardening and thickening of the walls of the arteries.
The condition can occur because of fatty deposits on the inner lining of arteries (atherosclerosis).
Calcification of the wall of the arteries, or thickening of the muscular wall of the arteries from chronically elevated blood pressure occurs.
As the deposits of fat and plaque begin to build the lumen of the arteries become reduced. If the plaque frees itself from the wall a blood clot may form. This may lead to coronary thrombosis (reduced blood flow to the heart).
When coronary arteries that supply blood to the heart muscle are effected a shortage of oxygen delivered to the heart itself may lead to a heart attack.
Coronary arteries supply heart muscles with oxygen and nutrients

36. Risk Factors in Coronary Heart Disease
6.2 A3 Causes and consequences of occlusion of the coronary arteries.
6.3 A1 Causes and consequences of blood clot formation in coronary
Risk Factors in Coronary Heart Disease
Factor
Causes
Genetics
Family history of high cholesterol/blood pressure
Age
Older people have a greater risk due to a loss in elasticity in arteries
Sex
Males have a greater risk then females
Diet
Increases in fat intake lead to higher levels of cholesterol and increase formation of plaque
Exercise
A lack of exercise increase risk. This is due to a weakening of circulation
Obesity
Increase in blood pressure which leads to increase plaque formation in the arteries
Stress
Stress has been linked to increased levels of the hormone Cortisol. Which has been show leads to a increase likelihood of atherosclerosis

37. Bibliography / Acknowledgments