Respiratory 2

• LOs:

  
• What does respiration refer to?

  Processes involved in exchange of O2 & CO2 between cells & external environment (O2 required for metabolism)
• What do regulatory mechanisms ensure?

  • Ventilation of lungs is matched with its blood supply (perfusion)
  • O2 supply & CO2 removal vary appropriately with activity

  E.g, during exercise more waste product made (blood pH more acidic) so respiratory system maintains acid base balance- hyperventilation increases breathing rate so more CO2 removed

  (example of homeostasis)
• What is hypoventilation?

  Slowing breathing- retains CO2 to make blood pH more acidic
• What does the pulmonary vein carry?

  Oxygenated blood to the heart
• Cardio-respiratory system diagram:

  
• What happens in the alveoli?

  Gas exchange

  Each alveolus has capillary network around it

  CO2 & O2 passively diffuse across
• Structure of lungs?

  • Trachea split into 2 bronchi
  • Bronchi split into bronchioles (have alveoli on their ends)
• What is breathing under the control of?

  Autonomic nervous system
• What happens during inspiration?

  Breathing in

  Diaphragm contracts

  Negative pressure caused so air moves into lungs down pressure gradient
• What is emphysema?

  Disease- affects efficiency of ventilation
• What does cellular respiration involve?

  Production of ATP in cells
• What does physiological respiration involve?

  Gas exchange
• When does alveolar dead space occur?

  Ventilation exceeds profusion (blood flow to alveoli) - insufficient gas exchange

  Caused by conditions that reduce blood flow to those parts of the lungs

  E.g, chronic lung diseases
• What is a collapsed alveolus?

  Alveolus deflated or closed

  Caused by blockages in airway by mucus or foreign object or tumour so air can't reach alveolus

  Shape changes but is still connected to blood

  PaO2 decreases
• Explain the sigmoid shape of hb and O2:

  For every O2 that binds to hb it increases affinity for next oxygen to bind

  Harder to bind at start but becomes easier due to cooperative binding

  Curve plateaus at end as hb fully saturated
• What can affect cooperative binding?

  • Temperature
  • pH
  • Carbon dioxide
• When might the curve shift to the right?

  High CO2 and low pH or high temperature
• When might the curve shift to the left?

  Low CO2

  high pH or low temperature
• How is CO2 transported?

  CO2 enters RBC

  Combines with water (catalysed by carbonic anhydrase)

  Forms carbonic acid

  Dissociates into H+ and bicarbonate

  H+ binds to hb to form deoxyhb (maintains pH balance)

  bicarbonate diffuses into blood plasma

  chloride ion enters RBC to maintain electrical neutrality
• What happens during respiratory acidosis?

  pH of blood drops (POCO2 increases)

  pH more acidic
• Where are chemoreceptors?

  Central chemoreceptors (brain-medulla oblongata)

  Detect changes in CO2 and pH in CSF

  Peripheral chemoreceptors (carotid)

  Detect changes in CO2 and pH
• What happens if CO2 levels too high?

  Central chemoreceptors trigger faster breathing

  Oxygen levels too low- peripheral chemoreceptors send signals to brain to breathe more
• What drives healthy people to breathe?

  CO2
• What drives people with COPD to breathe?

  O2