Transport in animals

• Describe 2 features of an open circulatory system ?

  transport medium of haemolymph

  few short vessels
• Give an example of an open circulatory system ?

  insects
• Define a closed circulatory system ?

  blood is fully enclosed within blood vessels at all times
• Single circulatory system = blood passes through the heart once for every circuit of the body
• What is a disadvantage of single circulatory system ?

  blood pressure drops on return, oxygen delivery is slow
• Double circulatory system = blood passes through a 4 chambered heart twice for every full circuit of the body
• give an example of single circulatory system ?


  fish
• Example of double circulatory system ?

  Human
• Advantage to double circulatory system ?

  High pressure maintained so delivery is efficient
• How come tissue fluid is able to form ?

  Due to the small gaps in the capillary walls which enable liquid to be forced out when pressure increases
• Hydrostatic pressure = pressure exerted by a liquid
• oncotic pressure =  osmotic pressure generated by plasma proteins in solution
• Name a plasma protein found in capillaries ?

  albumins
• How does tissue fluid form?

  When hydrostatic pressure is higher than oncotic pressure, there is a net movement out of the capillaries.
• Why is there high hydrostatic pressure at the arteriol end of a capillary ?

  The capillary is smaller in diameter than arteriol, due to decrease in volume pressure has increased
• What molecules are moved out of capillary into tissue fluid ?

  glucose, amino acid, fatty acids, ions and oxygen
• Which molecule remains in the capillary at all times ?

  plasma proteins
• Describe how tissue fluid is reabsorbed ?

  At venuole end oncotic pressure is higher than the hydrostatic pressure. Net movement of fluid into the capillary
• What is lymph ?


  Excess tissue fluid that does not get reabosrbed
• Where does lymph go ?

  Joins the lymphatic system where is eventually re-enters the blood stream
• What molecule will not be present in lymph ?

  plasma proteins
• Why do Atria have thinner walls ?

  They only need to exert a small force as they do not need to pump at high pressure
• Which ventricle walls are thicker and why ?

  Let ventricle, contraction with greater force to pump at higher pressure as blood leaving left ventricle must go around entire body
• What type of muscles are cardiac muscle ?

  myogenic
• myogenic = muscle contract is automatic
• Which artery supplies heart with blood ?

  coronary artery
• Which valve lies between left atrium and ventricle ?

  bicuspid
• Which valve lies between the right atrium and ventricle ?

  tricuspid
• What happens in diastole ?

  atria and ventricles are relaxed

  A.v valves are open

  semi-lunar valves are closed

  blood flows into atria/ventricles
• What happens in Atrial systole ?

  Atria contracts

  Atria volume decreases and blood flows out into the ventricle
• What happens in ventricular systole ?


  ventricles contract

  semi-lunar valves open and A.V valves shut

  blood flows into arteries
• cardiac output = heart rate x stoke volume
• stroke volume = volume of blood pumped out the heart in each beat
• Where is the SAN located ?


  Right atrium
• Where is the AVN located ?

  in the artia near the border of right an left ventricle
• bundle of His = runs through the septum
• Purkyne fibres = branches in the ventricle walls
• Apex of heart = bottom of heart
• What causes atrial systole ?

  SAN releasing a wave of depolarisation across the atria
• Describe the steps in controlling the rate of contraction

  1. SAN releases wave of depolarisation across atria
  2. Impulse reaches AVN, a pause occurs
  3. Wave of depolarisation is sent down the bundle of His and inoto apex of heart
  4. From apex it travels up purkyne fibres and ventricle contracts
  5. Cells repolarise