The Heart

• How do the lungs and circulatory system work together to allow efficient mass transport?


  • Carbon dioxide is removed quickly to the lungs from respiration
  • Oxygen is brought quickly from the lungs for respiration
  • Cells can carry out respiration continuously due to a constant supply of oxygen
• Adaptations of capillaries


  Walls one cell thick - short diffusion pathway.

  Narrow diameter - slows passage of rbc's and allows more diffusion to occur.

  Contain fenestrations - wbc's squeeze trough pores to combat infection.
• Adaptations of arteries


  • Smooth endothelium - reduces friction for free blood flow.
  • Layers of muscle cells strengthen artery - so withstand high pressure.
  • Muscle cells also allow constriction of the lumen - useful for diverting blood away from certain areas.
  • Elastic tissue stretches and recoils - maintains pressure gradient.
  • Contains collagen - protects blood vessels from damage by overstretching.
• Adaptations of veins


  Large lumen - reduces friction between the blood and the endothelium of the vein.

  Contain valves - prevent back flow of blood.

  Pulse is absent in veins - due to increased distance from the heart.
• what is the right side and left side of the hear separated by?

  septum - wall of muscular tissue to ensure that blood doesn't mix
• draw the heart structure


  ;

  
• right atrium and right ventricle are seperated by the

  tricuspid valve
• left atrium and left ventricle are seperated by

  the bicuspid valve
• structure and function of left ventricle

  thicker muscle than the right ventricle for contraction of blood all the way around the body
• function of av valves

  prevent backflow of blood from ventricles into atria
• function of sl valves

  prevent backflow of blood from arteries into ventricles
• structure and function of atria

  thin walled and elastic so they can stretch and fill with blood
• describe what happens during atrial systole

  the atria contract

  so pressure in atria is greater than ventricles, so av valves open

  blood is forced into ventricles so there is a slight increase in pressure as ventricles fill with blood
• describe what happens during ventricular sysole

  ventricles contract, increasing pressure

  so av valves shut to prevent backflow of blood but semi lunar valves open
• describe what happens during cardiac diastole

  ventricles and atria are relaxed

  semi lunar valves closed as pressure in venticles is lower than arteries

  atria fill with blood so av valves open

  process repeats
• describe how heart rate can be investigated practically

  1.Prepare five different concentrations of caffeine solution and a control solution of distilled water

  2.Add some pond water into the well of a cavity slide and add three drops of distilled water 

  3.Select a large Daphnia and use a pipette to carefully transfer it to the cavity slide

  4. Place the cavity slide onto the stage of a microscope and observe the animal under low power

  5. use a stopwatch and time 20s and count heart rate then x3.

  6. repeat with different caffine concentrations and take an average.
• describe the steps in atherosclerosis

  1. damage to endothelium i.e high blood pressure
  2. immflamatory response - accumulation of wbc's
  3. lipids, platelets cholestrol clump together to form a plaque
  4. atheroma narrows lumen of artery
  5. blood pressure is raised
• describe the blood clotting process

  1. platelets release thromboplastin in response to damage
  2. calcium ions and thromboplastin convert prothrombin to thrombin
  3. thrombin catalyses conversion of soluble fibrinogen into insolube fibrin
  4. fibrin mesh is formed, trapping platelets and rbc's
  5. clot is formed
• how can clots be detrimental to health

  1. clot can block the artery
  2. clots reduce blood flow
  3. therefore reduced oxygen in blood
  4. less respiration of surrounding cells
• what is a stroke

  a sudden loss of brain function in a localised area due to disruption of blood flow in the brain

  a stroke caused by a blood clot is an ischemic stroke
• how does a heart attack occur

  1. blood flow to certain areas of the heart is restricted so less oxyegn in the blood being delivered
  2. less respiration, so less atp released
  3. heart can no longer contract, reducing the force generated by the heart when it beats
  4. cells die, leading to myocardial infarction
• what are risk factors

  factors linked to an increased risk of a disease
• how can diet increase risk of cvd

  • diet high in saturated fat can increase blood cholestrol levels, therefore increasing atheroma formation
  • diet high in salt increases blood pressure
• how can high bp lead to cvd

  • increases risk of damage to artery walls
  • so increased risk of atheroma formation/thrombosis

  could be linked with stress, smoking etc
• how does smoking lead to cvd

  • carbon monoxide combines with heamoglobin, reducing its oxygen carrying capacity
  • decreases respiration in cells of brain and heart
  • nictine increases agglutination of platelets
  • smoking decreases antioxidants in blood, which are protective chemicals.
• how can genetics increase cvd

  • individuals may inherit alleles that make them more prone to high bp or cholestrol, increasing thrombosis risk
• how does age lead to cvd

  as age increases, the blood vessels bcome more fragile and plaque building up over time
• how does biological sex increase cvd

  men are x3 more likely to have cvd

  most likely due to lower levels of oestrogen which increases good levels of cholesterol in blood
• ethical considerations of using invertebrates

  • They cannot give consent to be studied
  • They cannot express pain
  • Some people believe it is more ethical to experiment with invertebrates than vertebrates as they have less sophisticated nervous systems and may not feel pain in the same way 
  • Animals should be handled gently
  • Examination periods should be kept as short as possible
  • Animals should be returned promptly to the holding tank after being examined
• why cant larger organisms rely on diffusion

  • diffusion distances are too great
  • larger organisms have high energy requirements, so delivery of reactants needs to happen quickly