IB Biology - Topic 6.2 + D.4: Cardiovascular System

draw and label a heart diagram

list and describe the role of the three parts that make up the cardiovascular system

1. the heart: pump blood by creating a pressure gradient

2. blood vessels: carry blood to and from the heart to other tissues

3. blood: medium in which the transport of materials such as nutrients is carried

list what the cardiovascular system transports

1. oxygen

2. nutrients

3. antibodies

4. hormones

5. heat

6. carbon dioxide

7. urea

list and describe the components of blood

1. plasma: dissolves or carries other components of blood

2. erythrocytes (red blood cells): transport oxygen in the hemoglobin

3. leucocytes (white blood cells):

   1. phagocytes: eat up pathogens + dead cells

   2. lymphocytes (b-cells, t-cells): for immune response

4. platelets: clotting of blood following damage to cells or erethrocytes

outline the basic flow of blood

1. deoxygenated blood enters the atria via the veins

2. atrial contraction pushes blood into the ventricles

3. ventricular contraction pushes blood out of the heart into the arteries to the lungs (pulmonary) OR body (systemic)

explain the features of the heart that keep blood flow constant

1. atrioventricular valves (tricuspid and mitral) prevent backflow

2. semilunar valves (pulmonary and aortic) prevent backflow

3. pressure gradient (higher pressure in the ventricles) pushes blood under pressure into the arteries

stroke volume

amount of blood pumped in a single contraction

cardiac output

volume of blood pumped into the systemic circulation per minute; depends on both heart rate and stroke volume

outline the path of deoxygenated blood

1. deoxygenated blood flows to the heart via the veins leading to the vena cava

2. deoxygenated blood enters the heart in the right atrium

3. atrial contraction pushes the deoxygenated blood into the right ventricle, past the atrioventricular valve (tricuspid valve)

4. ventricular contraction pushes the deoxygenated blood into the pulmonary arteries, past the semilunar valve (pulmonary valve)

5. pulmonary arteries lead to the lung for gas exchange to occur

*pulmonary arteries are the only arteries in the body that carry deoxygenated blood

outline the circulation of oxygenated blood

1. oxygenated blood returns to the heart in the left atrium via the pulmonary veins

2. atrial contraction pushes the oxygenated blood into the left ventricle, past the atrioventricular valve (mitral valve)

3. ventricular contraction pushes the oxygenated blood into the aorta, past the semilunar valve (aortic valve)

4. the aorta brings oxygenated blood to the rest of the body

*pulmonary veins are the only veins in the body that carry oxygenated blood

describe the structure and function of the arteries

• carry oxygenated blood away from the heart at high pressure to body tissues

• contain thick walls to withstand high pressure

  • have muscle cells and elastic fibers that assist in maintaining blood pressure and its movement

describe the structure and function of the capillaries

• permeable walls for rapid exchange of gases, nutrients, waste, and diffusion of phagocytes

• narrow so it can penetrate all parts of the tissue

• large total surface area

describe the structure and function of the veins

• collect blood at low pressure from body tissues and return it to the heart

• thinner walls than arteries because they face lower pressure, allows them to be squeezed by muscles

• fewer muscles + elastic fibers than arteries because they face lower pressure

• valves are present to prevent backflow or pooling of blood

cardiomyogenic muscle contraction

myogenic contraction is contraction initiated by the cell itself rather than a nervous stimulus; heart beat doesn’t rely on impulses from the brain to keep contracting

sinoatrial node

sets the pace and initiates the heartbeat by sending the first signal and causes the atria to contract; it can be independent or moderated by the autonomic nervous system

atrioventricular node

triggered by the signal of the SA node, carries out signal for ventricular contraction; between the SA node and VA node there is a delay that allows the switch from diastole to systole

outline the steps of the spread of the electrical signal

outline the events of the cardiac cycle

1. SA node receives signal to fire when the ventricles are 70% full (during late ventricular diastole)

2. AV valves (mitral + tricuspid) open and ventricles are filled to the max (atrial systole)

3. pressure increase in the ventricles closes the AV valves (ventricular systole)

4. AV nodes fire

5. Purkinje fibers carry impulse to all areas of ventricles for simultaneous fire

6. pressure increase causes semilunar valves (pulmonary + aortic) to open

7. blood is pumped from ventricles to pulmonary arteries/aorta (systole sound) (ventricular systole)

8. pressure decrease in the ventricles closes the SA valves (diastole sound)

9. pressure in the ventricle is lower than in the atria so the AV valves open

10. blood volume increases in ventricle (70%)

11. both atria + ventricles are relaxed (diastole)

12. atria receives blood from veins

13. cycle repeats

cardiac cycle summed up

describe and explain the adaptations to carry electrical signal

• branched cells with intercalated discs that prevents separation under strain of pumping blood and signal can be passed quickly

• large interconnected network is created allowing easier propagation