Organisation

• Temperature effect on enzymes

  Up to a certain point, increasing temperature increases enzyme action, as molecules have a higher kinetic energy. Above a certain temperature, the shape of the active site is altered and the enzyme becomes denatured, so it can no longer catalyse the reaction. The optimum temperature is around 37
• Heart


  An organ that pumps blood around the body
• Double circulatory system

  1. One pathway carries blood from the heart to the lungs - where the gaseous exchange of oxygen and carbon dioxide takes place

  2. One pathway carries blood from the heart to the tissues
• Purpose of coronary arteries

  Supply the heart muscle with oxygenated blood
• Blood flow through the heart

  1. Blood enters the right atrium via the vena cava, and the left atrium via the pulmonary vein

  2. The atria contract, forcing blood into the ventricles and causing valves to shut

  3. After the ventricles contract, blood in the right ventricle is pumped to the lungs, and blood in the left ventricle is pumped to the body
• Valves in the heart

  Prevent the backflow of blood
• Coronary arteries


  Supply the heart muscle with oxygenated blood
• Blood flow through the heart

  1. Blood enters the right atrium via the vena cava, and the left atrium via the pulmonary vein

  2. The atria contract, forcing blood into the ventricles and causing valves to shut

  3. After the ventricles contract, blood in the right ventricle enters the pulmonary artery (to the lungs) and blood in the left ventricle enters the aorta (to the body)
• The approximate value of the natural resting heart rate is 70 beats per minute
• Heart rate control

  Heart rate is controlled by a group of cells in the right atrium which act as a pacemaker. They release waves of electrical activity which cause the heart muscle to contract.
• Abnormal heart rhythm treatment

  Irregular heart rhythms can be treated using an artificial pacemaker, which sends out electrical signals to correct the heart's rhythm.
• Types of blood vessels

  • Arteries
  • Veins
  • Capillaries
• Arteries

  • Thick muscle layer - adds strength to resist high pressure
  • Thick elastic layer - allows arteries to stretch and recoil - in order to withstand high pressure
• Veins

  • Wide lumen - enables low pressure
  • Valves - prevent backflow of blood
• Capillaries


  • Walls are one cell thick - short diffusion path
  • Permeable walls - substances can diffuse across
  • Narrow lumen - blood moves slowly - more time for diffusion
• Blood flow rate calculation

  Volume of blood / number of minutes
• Location of lungs

  The lungs are located in the thorax (within the chest). They are protected by the ribcage and separated from the rest of the abdomen by the diaphragm.
• Tissues and organs of the gas exchange system

  • Trachea
  • Intercostal muscles
  • Bronchi
  • Bronchioles
  • Alveoli
  • Diaphragm
• Lung ventilation by intercostal muscles

  1. Intercostal muscles contract

  2. Ribcage moves upwards and outwards

  3. Diaphragm flattens and volume of the chest increases

  4. Increased volume results in decreased pressure

  5. Air is drawn into lungs down pressure gradient
• Gas exchange at the alveoli

  1. Oxygen diffuses from the alveoli into the capillary bloodstream down its concentration gradient

  2. Carbon dioxide diffuses from the capillary into the alveoli down its concentration gradient
• Alveoli adaptations for gas exchange

  • Small and arranged in clusters - larger surface area
  • Rich blood supply - maintains concentration gradient
  • Thin alveolar wall - short diffusion pathway
• Breathing rate calculation

  Number of breaths / number of minutes
• Substance that carries blood components

  Plasma
• Substances transported by plasma

  • Red blood cells
  • White blood cells
  • Platelets
  • Carbon dioxide
  • Urea
  • Products of digestion
• Plasma


  A yellow liquid within blood that transports substances around the body
• Purpose of red blood cells

  Transport of oxygen around the body
• Red blood cell adaptations

  • Biconcave shape - increased surface area to volume ratio
  • No nucleus - more room for haemoglobin to bind to oxygen
  • Contain haemoglobin - binds to oxygen
• Purpose of white blood cells

  They form part of the immune system, which protects the body from invading pathogens
• White blood cell adaptations

  • Have a nucleus - contains DNA which codes for proteins
  • Can produce antibodies
  • Can produce antitoxins
  • Can engulf and digest pathogens (phagocytosis)
• Purpose of platelets

  Platelets are small cell fragments which aid the clotting of blood at the site of a wound
• Importance of platelet function

  Platelets aid in the process of blood clotting (conversion of fibrinogen to fibrin). As a result, red blood cells are trapped in the fibrin network, forming a clot which prevents excessive bleeding. Scab formation (after the clot has dried) prevents bacteria from entering the wound.
• Coronary heart disease

  Coronary heart disease occurs when the coronary arteries that supply the heart muscle become blocked with a buildup of fatty material. This restricts the supply of oxygen to the heart, possibly leading to a heart attack or death.
• Stent

  A stent is a metal mesh tube that is inserted into a blocked artery so that it remains open. The stent is inflated using a balloon, which is later removed to allow blood to flow freely.
• Advantages and disadvantages of stents

  • Advantages: Insertion can be carried out without general anaesthetic, Quick recovery time, Lower the risk of a heart attack
  • Disadvantages: Risk of postoperative infection, Risk of blood clots at site of stent
• Statins


  Statins are drugs which reduce the level of LDL (bad) cholesterol which contributes to the development of coronary heart disease.
• Advantages and disadvantages of statins

  • Advantages: Reduce risk of strokes, coronary heart disease and heart attacks, Increase level of HDL (good) cholesterol
  • Disadvantages: Have to be taken continuously, May have side effects, Effect may not be immediate
• Heart bypass surgery


  A surgery where blocked coronary arteries are replaced
• Statins


  Drugs which reduce the level of LDL (bad) cholesterol which contributes to the development of coronary heart disease
• Heart bypass surgery


  A surgery where blocked coronary arteries are replaced with sections of veins taken from other parts of the body
• Types of valves that can replace leaky valves

  • Mechanical - made of metal or polymers
  • Biological - taken from animals (pigs, sometimes humans)