O2 and CO2: exam 3 applied phys

what determine whats dissolved in plasma?

PO2 and PCO2 partial pressures create a gradient that goes down its gradient (high to low) along with its solubility

alveolar air of PO2?

150mmHg lowered to 100mmHg
changes little when ventilation increases

alveolar air of PCO2?

40mmHg
changes a lot with small changes in ventilation

main driver of controlling breathing?

PCO2 in regards to H+ in the brain

rate of O2 diffusion goes up with that four factors?

-increased difference between alveolar PO2 and venous PO2
-increasing surface area
-membrane thickness decreases
-solubility increases

what is venous PO2?

40mmHg

what is venous PCO2?

46mmHg

difference between venous and arterial?

venous blood leaves tissues to return to heart and lungs so reflects tissues
arterial blood leaves lungs and is going to tissues

arterial PO2 and PCO2?
venous PO2 and PCO2?

100/40
40/46

what percentage of O2 is poorly soluble in plasma that is keeping us alive?

1.5%

what percentage of O2 is attached to hemoglobin (bound to heme of hb in circulation)?

98.5%

is reduced hb combined with O2? what does it pick up?

no
picks up H+ and CO2 in tissues

at lungs, do we drive toward hb and O2 OR hbO2 (oxyhb)?

oxyhb due to lot of free O2 and hb

at tissues, do we drive toward hb and O2 OR hbO2 (oxyhb)?

lot of oxyhb so hb releases O2

as blood PO2 falls, hb releases more or less O2

more

less than PO2 of 60mmHg does what?

drives respiration

what causes a right shift?

high PCO2, high H+ (low pH), high temperature, or high 2,3 BPG

fake left shift (pathologic not physiologic like right shift)?

CO (carboxyhb)
CO doesn’t load 100% and doesn’t release it at tissues
Heme likes CO 300x more than it likes oxygen

what percentage of CO2 is transported as bicarb (needs carbonic anhydrase to convert CO2 and water to H2CO3 to H+ and bicarb)?

60%

Why doesn’t bicarb combine with H+?

• Bicarb (extracellular) pumped out before being able to recombine

• H+ buffered by hemoglobin (intracellular)

  • H+ binds to HbO2 which causes O2 affinity to drop with hb and releases oxygen

  • Hb can bind to H+ or CO2 which decreases hb affinity for O2

chloride shift?

HCO₃⁻ leaves the red blood cell into the plasma in exchange for Cl⁻ entering

systemic vs pulmonary circulation of O2 and CO2 and hb?

At the tissues:

• CO₂ diffuses into the red blood cell and is carried three ways:

  • as bicarbonate, formed by carbonic anhydrase (CO₂ + H₂O → H⁺ + HCO₃⁻)

  • bound to Hb (carbaminohemoglobin, HbCO₂)

  • dissolved in plasma

• Chloride shift: HCO₃⁻ leaves the RBC for plasma, and Cl⁻ enters.

• Hb buffers the H⁺ (Hb + H⁺ → HbH).

• The H⁺ and CO₂ lower Hb’s affinity for O₂ (Bohr effect), so more O₂ is released.
  
  

At the lungs:

• Everything reverses.

  • HbCO₂ → Hb + CO₂

  • HbH → Hb + H⁺

  • H⁺ + HCO₃⁻ → H₂O + CO₂ (carbonic anhydrase)

• The chloride shift reverses: HCO₃⁻ enters the RBC and Cl⁻ leaves.

• Dissolved CO₂ diffuses out to the alveoli to be exhaled.

• Hb takes up O₂ again.

• Losing H⁺ and CO₂ raises Hb’s affinity for O₂, so it loads fully. This is the Haldane effect, which also helps release CO₂.

The tissues have low O₂ and high CO₂, so O₂ leaves and CO₂ enters. The lungs are the opposite, so O₂ enters and CO₂ leaves. Hb picks up or drops O₂, H⁺ and CO₂ accordingly

what part of the medulla respiratory center is the pacemaker?

Rostral Ventromedial Medulla Pre-Bötzinger Complex

what part of the medulla respiratory center stimulates quiet inspiration (active) and has passive expiration?

Dorsal Respiratory Group (DRG)

what part of the medulla respiratory center stimulates active inspiration and expiration neurons?

ventral respiratory group (VRG)

pons respiratory centers is in charge of

fine tuning

which center of the pons limits duration of inhalation by the DRG?

Pneumotaxic center

which center of the pons prevents inhibition of the DRG?

apneustic center

what directly depresses the central chemoreceptors and the respiratory center itself when <60 mm Hg (not helpful)

low PO2 in arterial blood

what strongly stimulates central chemoreceptors; is the dominant control of ventilation. 

(Levels >70–80 mm Hg directly depress the respiratory center and central chemoreceptors) -death is occurring

high PCO2 in arterial blood (high H+ in brain ECF)

what stimulates peripheral chemoreceptors?

high H+ in arterial blood
low PO2 in arterial blood when it is less than 60mmHg

what makes up the peripheral chemoreceptors?

carotid bodies (carotid sinus/artery) and aortic bodies (aortic arch)

what makes up the central chemoreceptors?

medulla in brain