21 November 2011 Respiratory Physiology Announcements: Remaining topics: Respiration and Renal Test # 3 Monday Dec 5th: CV, Resp, & part of Renal Feedback on Hemorrhage Diagrams: TAs and Schedule Chapter questions for CV and Respiration questions are posted.

1QQ 30 for 8:30 What would alveolar minute ventilation be in a person who is breathing 10 breaths per minute and has a typical tidal volume and typical dead space volume? Show your work. Suppose a 25 year old man were unable to produce sufficient levels of surfactant. Would he have difficulty inhaling? Exhaling? Why or why not?

1QQ 30 for 9:30 What would alveolar minute ventilation be in a person who is breathing 20 breaths per minute and has a typical tidal volume and typical dead space volume? Show your work. Why do prematurely born infants have difficulty inhaling but not exhaling?

Where are receptors for negative feedback loop? Gas exchange

Peripheral Chemoreceptors Carotid bodies (not carotid sinuses which are baroreceptors) Aortic bodies (not aortic arch baroreceptors) Central Chemoreceptors in medulla (sensitive to H+ in interstitial fluid of medulla) To ponder: Why should there be three sets of chemoreceptors?

Carbon Dioxide reacts with water! CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3- Carbonic Acid Bicarbonate H+ can’t cross Blood Brain Barrier but CO2 does! Central Chemoreceptors respond to H+ produced by diffusion of CO2 into brain interstitial fluid.

In what forms are O2 and CO2 found in the blood? Gas exchange

Partial Pressures are the same, but total oxygen content differs! Figure 13.27 Bound & Free CO2 and O2 bound to Hb do not contribute to partial pressure (no longer a dissolved gas!) Peripherial chemoreceptors can detect ONLY dissolved gasses!

Figure 13.31 Hb can bind O2, CO2, and H+ 100 40 100 Increases in CO2 and H+ decrease the affinity of Hb for O2

Steep Flat

Shifting the Oxyhemoglobin dissociation curve At 40 Torr, more DPG, higher temperature, and greater acidity (all indicative of increased metabolism) shift dissociation curve down (Hb has a lower affinity for O2) and thus more O2 is unloaded into the tissues. Notice the main affect is on the steep portion of the curve which means that there is little influence on the loading of O2 onto Hb in the lungs

Table 13.09

Figure 13.34 Ventilation is relatively unaffected by PaO2 until it falls below 60. Explain why!

Carbon dioxide transport carbaminohemoglobin Chloride Shift CA = carbonic anhydrase Hb is a Buffer Carbon dioxide transport

40 46 carbaminohemoglobin 40 46

Any deviation from the set point for CO2 Causes immediate changes in ventilation! Why should this be so?

Carbonic Acid Bicarbonate CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3- Carbonic Acid Bicarbonate