L8A: Respiratory system (gas transport & movement)

• What dictates the movement of dissolved gases?

  Pressure differentials
• What percentage of oxygen is chemically combined to haemoglobin?

  98-99%
• What percentage of oxygen is dissolved in blood?

  1-2%
• What does the amount of oxygen dissolved in plasma depend on?

  Solubility and partial pressure in lungs
• How much oxygen is carried dissolved per 100ml plasma?

  0.3ml
• How can the dissolving capacity of oxygen be increased?

  By administering 100% oxygen at high pressure
• What is haemoglobin's efficiency as an oxygen carrier?

  Highly efficient, carries 98%
• Where is haemoglobin contained?

  Within red blood cells
• How many haemoglobin molecules does each RBC contain?

  270 million
• What are the components of haemoglobin?

  4 haem groups and 4 globin groups
• What is cooperative binding in haemoglobin?

  First oxygen binding increases affinity for more oxygen
• What is haemoglobin with oxygen called?

  Oxyhaemoglobin
• What is haemoglobin without oxygen called?

  Deoxyhaemoglobin
• How much oxygen is carried per 100ml plasma?

  18.8ml
• What factors can alter haemoglobin's affinity for oxygen?

  pH, carbon dioxide concentration, body temperature
• What increases haemoglobin's affinity for oxygen?

  Increased pH and decreased carbon dioxide
• What decreases haemoglobin's affinity for oxygen?

  Decreased pH and increased carbon dioxide
• What is the Bohr effect?

  Increased carbon dioxide lowers pH, increasing oxygen release
• How does anaemia affect oxygen carrying capacity?

  Reduces total number of haemoglobin molecules
• What percentage of carbon dioxide is dissolved as carbon dioxide?

  10%
• What percentage of carbon dioxide is attached to globin in RBC?

  30%
• What percentage of carbon dioxide is in bicarbonate form?

  60%
• What is the reaction for carbon dioxide transport?

  Carbon dioxide + water <> carbonic acid <> hydrogen + bicarbonate
• What role does carbonic anhydrase play in carbon dioxide transport?

  Increases rate of bicarbonate formation
• What happens to carbonic acid when formed?

  Dissociation is instantaneous, generating bicarbonate and hydrogen
• What is the chloride shift?

  Bicarbonate leaves RBC in exchange for chlorine
• How does carbon dioxide move into RBC?

  Binds to haemoglobin or water, forming bicarbonate
• What occurs in the lungs regarding PO2 and PCO2?

  High PO2 and low PCO2 reverses blood conditions
• What happens when oxygen binds to heme in the lungs?

  Releases hydrogen and uncouples carbon dioxide from globin
• What builds up in cells as carbon dioxide and hydrogen diffuse out?

  Chlorine will diffuse out, bicarbonate re-enters
• What components are needed to reverse the bicarbonate reaction?

  Carbon dioxide and water
• What is required for muscles associated with ventilation to contract?

  Continuous stimulation from CNS
• Where do nervous signals for respiration come from?

  Respiratory centre in pons and medulla
• What is the structure of the respiratory centre?

  Two dense bilateral aggregates of neurons
• How many respiratory centres are there?

  Four
• What does the dorsal group of neurons control?

  Signals diaphragm through phrenic nerve for inspiration
• What does the ventral group of neurons control?

  Both inspiration and expiration
• What is the role of the apneustic centre?

  Promotes inspiration
• What does the pneumotaxic centre do?

  Switches off apneustic centre allowing expiration
• What are the apneustic and pneumotaxic centres considered?

  Pacemakers of the respiratory system