Respiratory System - CO2 and Regulation

Question 1

Co2 transport in blood

Answer 1

• CO2 carried from tissue into plasma and then diffuse into rbc and then to lung and released
  
  • CO2 from metabolism, etc. so goes from skeletal muscle to blood to rbc
• in rbc: Co2 combines w/water to form H2Co3 and that becomes bicarbonate and H+
  
  • to keep it going we take bicarbonate out of cell and bring in Cl- called chloride shift since antiporter
• most of our Co2 is transported as bicarbonate in the plasma - main rxn
• Hb can interact w/hydrogen ions and hydrogenate Hb and release more O2 (thats why have shift in O2 curve when acidic)
• CO2 promotes release of more O2 by makes carbamino Hb
  
  • when O2 low and Co2 are high we can promote bicaronate and other rxns

Question 2

In lung w/Co2

Answer 2

• in lung O2 is high and CO2 is low and getting to equilbrium, so these rxns in rbc reverse
  
  • take bicarbonate back in and drive rxn in reverse to make Co2 and water and blow off Co2
  • HCO3 + H+ –> H2Co3 –> H2O + CO2
  • O2 + HHb –> H+ + HbO2
  • O2 + HbCO2 –> HbO2 + CO2
  • one direction in tissue and other in lung
  • Haldane effect - higher levels of O2 bumps Co2 off hemoglobin

Question 3

Regulation that is autonomic via medulla

Answer 3

• respiration is autonomic and set up by the medulla
  
  • influenced by blood chemistry, blood pressure and exercise
• pneumotaxic center has some influence on medulla to refine basic rhythm
• medulla is right above spinal cord and is respiratory center - sets basic breathing rhythm
• chemoreceptors are at medulla
• spinal cord w/spinal motor neurons to control muscles

Question 4

Chemoreceptors monitor CO2

Answer 4

• chemoreceptors - give info to medulla which carries stuff out
  
  • “peripheral” on aortic and carotid bodies can also respond (not as sensitive as central)
    
    • more responsible for sensitivity to change in O2
  • “central” in medulla ( ventral side) are sensitive to > in pCo2 and < pH
• arterial pO2 is 100 and pCo2 is 40
• chemoreceptors generate compensatory response
  
  • if see > Co2 then > respiratory rate and respiratory volu w/> alveolar ventilation
    
    • increase RMV and rate and depth
    • not ventilating lungs properly
• “hypercapnia” type of hyperventilation to blow off CO2
• if see change in O2 then need to < O2 to about 40 to get a response then need to > RMV
  
  • therefore see that chemoreceptors are more responsive to change in CO2 than O2
• Co2 production in tissues is linked to change in pH so monitoring Co2 helps regulate pH due to metabolism b4 issues

Question 5

Blood Pressure

Answer 5

• regulate via baroreceptors (detect pressure changes) in carotid arteries (go to head)
• < in bp means O2 delivery could be compromised so baroreceptors send signal to medulla –> medulla increases respiratory rate (RMV) which is the compensatory response
• in fear, > RMV because override chemoreceptors

Question 6

Exercise

Answer 6

• increase RMV by increase rate and depth
• why? look at pO2 and pCO2 on venous circulation (coming back from muscles) vs. arterial side (supply approp O2 to tissue)
• arterial: 100 of pO2; 40 pCo2
• venous: decrease pO2 and increase pCo2 since doing exercise so muscles more Co2 and use more o2
• chemoreceptors are on arterial side where stuff looks normal, so changes not due to blood gases
• cerebellum medulla - higher brain centers that are involved in motor coordination drive this >
  
  • horses have RMVs coordinated w/each of mvmts