The Heart

• Define the cardiac cycle.

  One full heart beat, normal range in a human is 60-80bpm.
• What does a lower heart rate indicate?


  A better cardiac health overal
• Why is the cardiac cycle a mysogenic movement.

  It is an involuntary action, despite needing to contract and relax the movement requires no energy.
• What are the 3 stages of the cardiac cycle?

  Atrical systole (contraction)

  Ventricle systole (contraction)

  Both then diastole (relax)
• How is the cardiac cycle performed in the body?

  The sinoatrial node stimulates electrical signals. The fibres from the SA node connect both atriums, causing simultaneous contractions.

  The atrioventricular node delays the signals received from the SA node

  Bundles of His then carry the signals to the ventricles through the interventricle system, causing these to contract.
• Why must the signals from the SA node be delayed

  To allow blood to flow into ventricles
• What do the bundles of His branch into and what is their use?

  Purkinji fibres, these carry electrical signals to the bottom of the ventricle. Causing the contraction to start from the bottom an builds up pressure during it. This pressure then forces blood around the heart.
• What is haemogoblin's quaternary structure?

  4 polypeptide chains, each called a goblin

  A haem is contained within each polypeptide chain

  Each haem has iron inside

  Can carry 4 oxygen molecules at a time
• Define partial pressure

  Amount of / concentration of a molecule
• Define affinity

  How much a molecule 'likes' / wants to bind to haemogoblin
• State how O2 binding is reversible

  At the lungs O2 wants to bind to Haemogoblin (associate / loading)

  When at respiring the O2 wants to unbind from Haemogoblin (disocciate / unloading)
• Define how O2 binding happens to Haemogoblin / the O2 association curve.

  The first O2 molecule binding is hard and slow to do

  Once bound causes the haem to slightly change the tertairy structure. (Called co-operative binding), allowing other O2 molecules to bind

  4th O2 takes longer to bind due to less haem space to bind to
• What happens to the association curve of O2 if there is a higher or lower concentration or CO2 is present.

  Higher: Curve shifts to right

  Lower: Curve shifts to the left
• Define the Bohr Affect.

  Addition of CO2 shifts the graph to the right, causing affinity to decrease. Happening in respiring tissue, the pH becomes slightly acidic which changes the tertiary structure of haemogoblin into one with lower affinity.

  Removal of CO2 shifts the graph to the left, causing affinity to increase. Occurring in the lungs, the pH of blood becomes neutral. Tertiary stucture of Haemgoblin changes to one with high affinity.
• What happens to the affinity of Haemogoblin in an organism in higher altitude?

  Affinity increases because amount of O2 available decreases - making it more effecient
• What happens to the affinity of an organism with a high SA:V ratio?

  Affinity decreases, due to easier transport of gases and fewer specialised systems needed.