topic 4

• counter current gas exchange system means there is a large concentration gradient between the blood and the water, increasing the rate of aerobic repiration for more energy for more swimming
• The process of fish breathing:

  1. Mouth opens
  2. operculum opens
  3. raised mouth floor
  4. decrease in volume and increase in pressure
  5. water leaves
• the gills are covered by thin skin called opercular membrane which prevents water from entering the body cavity
• insects breathe through spiracles (holes) that open to tracheae (tubes)
• insect respiraton:

  O2 diffuses down the trachea, connected to the spiracles. The tracheoles are connected to the which carry the o2 into the muscles and body cells
• In insects, CO2 diffuses out of the cells along the tracheole walls and then back into the air via the spiracle.
• Spiracles have valves so when an insect breathes in or out, it only allows air to flow one way
• Artery: A blood vessel that carries blood away from the heart. it has a medium sized lumen, elastic fibres and smooth muscle
• Vein: A blood vessel that carries blood to the heart. These have a thinner wall than arteries and a very large lumen
• Capillary: A very small blood vessel that connects arteries and veins. This is the site of gas exchange
• The circulatory system consists of the heart, blood vessels (arteries, capillaries and veins) and blood
• LORD: left Oxgenated Right De-oxygenated
• Cardiac cycle: Atria systole

  Atria contracts

  AV valve opens

  blood moves into the ventricles
• Cardiac cycle: ventricular systole

  Ventricles contract

  AV valve closes

  Semilunar valve opens

  blood moves to the body
• Cardiac cycle: cardiac diastole

  Atria and ventricles relax

  Pressure decreases

  Semilunar valve closes
• Pulmonary vein - Lungs to the left atrium
• Aorta - Heart to the body
• Vena cava - Body to the heart
• Pulmonary artery - Heart to the lungs
• Myogenic stimulation: stimulation of skeletal muscle by nerve impulses
• 1. Myogenic stimulation: P wave

  Sinoatrial node - a myogenic wave of electricity washes over the cardiac muscle cells in both atria
• 2. Myogenic stimulation: Q wave

  Electrical signals gather at the atrioventricular node and are held for a short amount of time
• 3. Myogenic stimulation: signal travels down the His R/S wave
• 4. Myogenic stimulation: signals are turned upwards via conducting tissue T wave
• Blood clotting: Blood clots to stop blood loss and to prevent infection.

  A plug is formed and releases clotting factors - THROMBOPLASTIN

  Prothrombin changes to become its active form - THROMBIN

  Soluble fibrinogen forms insoluble fibrin to cover the wound
• Atherosclerosis: A build-up of fatty material in the arteries.

  Endothelium cells are damaged

  Increasing the risk of blood clotting in the artery leading to inflammatory responses causing white blood cells to move to the site of the damage

  White blood cells + Cholesterol + Calcium salts + Fibres build up and harden leading to the forming of plaque

  These then narrow the artery thus increasing blood pressure
• There is a high affinity for O2 in the lungs
• The higher the partial pressure, the more dissolved gas there will be.
• Higher temperature increases diffusion rate as particles have more energy
• Myoglobin: has a higher affinity for oxygen and is only 1 subunit
• Haemoglobin: Has a lower affinity for oxygen than fetal haemoglobin and is made from 4 subunits (alpha beta)
• Fetal heamoglobin: has a higher affinity for oxygen than adult heamoglobin
• Fetal haemoglobin can bind to oxygen at a low affinity, this is because at such low levels the oxygen from the mothers haemoglobin is dissociating meaning that fetal haemoglobin can use it
• Association (loading) of oxygen on the haemoglobin happens in the lungs
• Dissociation (unloading) of oxygen occurs in the tissue cells
• The Bohr effect states that when CO2 concentration increases, Hb will release O2 faster than normal
• Affinity is the degree to which one substance combines with another, haemoglobin has different affinities for oxygen molecules under different conditions.
• When oxygen concentration is high, haemoglobin has a high affinity for oxygen
• When oxygen concentration is low, haemoglobin has a low affinity for oxygen
• Haemoglobin changes its affinity for oxygen by changing its shape when in the presence of certain substances