Topic 1

• Describe an open circulatory system

  Blood is not contained in blood vessels but circulates in large spaces
• Define a closed circulatory system

  Blood is enclosed within vessels/diffusion of substances only takes place within vessels
• Define a single circulatory system

  "Blood flows through the heart once for each complete circuit of the body
• Blood is pumped at a low blood pressure. Suitable for organisms with a low metabolic rate"
• Define a double circulatory system

  "Blood flows through the heart twice for each complete circuit of the body (i.e simultaneously pumps to lungs and heart)
• Maintains a high blood pressure to meet demands of a high metabolic rate"
• Why cant complex multi cellular organisms rely on diffusion to transport substances around the body?

  They are too large for diffusion to transport substances quickly enough (small SA:V)
• How does blood circulate in an open circulatory system?

  A simple heart pumps blood out into the cavities surrounding the organs. The heart muscle relaxes so the pressure decreases and blood is drawn from the cavity back into the heart through open valves
• Why is a closed circulatory system more efficient?

  The blood is forced through fairly narrow tubes so it travels faster and under pressure.
• What are the benefits of a mass transport system?

  Carries raw material from specialised exchange organs to the body cells to remove metabolic waste
• Why is water a polar molecule? Oxygen is more electronegative than Hydrogen so there is a slight difference in charge between the atoms.
• Why is water a polar molecule?

  Oxygen is more electronegative than Hydrogen so there is a slight difference in charge between the atoms.
• Why does water remain a liquid over a wide range of temperatures?

  Hydrogen bonding holds water molecules together and collectively they make water very stable
• Why is water cohesive?

  the delta positive H is attracted to the delta negative O. This helps water to flow so it is good at transporting substances
• Why is water a good solvent?

  Polar molecules and ionic substances dissolve in water because water is dipolar. The forces of attraction between the delta positive H and the delta negative O are stronger than the ionic bonds so the ions become hydrated and completely surrounded by water molecules
• Describe the structure of capillaries

  Very narrow lumen for short diffusion distance, single layer of cells so it can lie very close to the cells. joins the arteries and venues together, medium pressure, large surface area - Structure of the capillaries
• What is the function of the capillaries?

  Where metabolic exchange occurs so substances are exchanged between cells and the capillaries -
• Describe the stretch and recoil in arteries

  Heart contracts and blood is forced into the arteries. The elastic walls stretch a little to accommodate the blood. The heart relaxes and the elasticity of the walls causes them to recoil a lot behind the blood pushing it forward. This causes a pulsing flow through the arteries
• Describe how blood flows in veins

  Blood flow is assisted by the contraction of skeletal muscles during movement of limbs and breathing. Low pressure in thorax when breathing draws blood back into the heart from veins -
• State the four chambers of the heart

  Left atria/left ventricle/right atria/right ventricle
• State the four vessels entering/exiting the heart

  aorta/vena cava/pulmonary artery/pulmonary vein
• How is the left side of the heart identified?

  Presence of a thicker muscular wall
• What is present inside the heart to prevent backflow?

  AV valves (tricuspid = right, bicuspid = left) and semi-lunar valves.
• Why are the ventricle walls thicker than atria walls?

  Blood needs to be under higher pressure to travel a further distance
• Why are valves important?

  Prevent backflow/allow build up of pressure
• State what happens to the heart during ventricular diastole and atrial systole

  Ventricles are relaxed/atria contract/increases pressure in atria/AV valves open/blood flows into ventricles
• State what happens to the heart during ventricular systole and atrial diastole

  Atria relax/ventricles contract/increase pressure in ventricle/AV valves shut/SL valves open/blood forced into arteries (pressure currently lower in arteries)
• State what happens to the heart during cardiac diastole

  Atria and ventricles relax/higher pressure in arteries causes SL valve to shut/atria begin to fill again/as pressure in ventricles drops, AV valves begin to open
• What valves are open during ventricular systole?

  SL valves
• Why are daphnia a good model organisms?

  Simple nervous system - feel no pain/transparent so can see heart beat/open circulatory system so substances can easily diffuse/invertebrate
• CPAC 1 - Daphnia heart rate: State the IV/DV/CV

  IV: Conc. Of caffeine/DV: Heart rate (min)/CV: volume/time/species/age/light intensity
• What can damage the endothelial lining?

  High blood pressure/smoking
• What is atherosclerosis?

  The hardening of arteries due to build up of plaque which blocks/narrows the arteries
• What happens during the inflammatory response?

  White blood cells leave the blood vessel and move into the artery wall
• How does an atheroma form?

  White blood cells accumulate chemicals especially cholesterol and this deposit builds up
• How does a plague form?

  Calcium salts and fibrous tissue also build up forming a hard swelling called a plaque on the inner artery wall. This build up of fibrous tissue causes the artery wall to lose some elasticity so it hardens.
• How can an atheroma increase the risk of thrombosis in arteries?

  An atheroma can rupture the endothelium of an artery, damaging the wall and leaving a rough surface. This triggers thrombosis at the rupture site
• Where is thromboplastin released from?

  It is a protein released from the damaged blood vessel and from platelets which have stuck to the damaged blood vessel wall
• What do thromboplastin and calcium ions from plasma do?

  The trigger the conversion of prothrombin into thrombin.
• What does thrombin do?

  Catalyses the conversion of fibrinogen into fibrin.