Lecture 29 Flashcards
Describe why adding hemoglobin helps
O2 has a low solubility in the plasma, so even at regular PO2, there is a low concentration of O2 in the plasma. Adding hemoglobin will increase the O2 carrying capacity of the blood (another “transport/storage” location
How can O2 be transported in the blood? and how does transfer work?
in the blood as free O2, bound to hemoglobin as HbO2
At the lungs, pressure gradient drives O2 into plasma, converted to HbO2. At the cells, pulls O2 out of plasma, causes HbO2 to dissociate
What does P50 represent?
the PO2 at which Hb is 50% saturated. Higher P50 = lower affinity, since you need a higher O2 in order to bind O2 to Hb
How does pH and CO2 change the O2-Hb curve?
pH indicates an increase in CO2, causes further dissociation (higher p50) so that more O2 released to the cells, therefore there is a shift to the right.
How is CO2 transported in the blood?
some as free CO2, more as HbCO2, most as bicarbonate
H2O+CO2 = H2CO3 via carbonic anhydrase, then dissociates to HCO3- and H+, H+ bound by hemoglobin
bicarbonate pulled out of the RBC via a Cl/HCO3- exchanger into the plasma, at the lungs, HCO3 pulled back in to recreate CO2
How is ventilation regulated?
1) Central chemoreceptors
CO2 in the cerebral capillary diffuses across the blood brain barrier. Does CA equation in the cerbrospinal fluid, produces H+. CO2 and H+ act on the chemoreceptor at the medulla, sends signal down neuron to respiratory control centers to increase ventilation.
2) Peripheral chemoreceptors
chemoreceptors in the aortic arch and carotid artery mainly respond to PCO2 and PH but respond to PO2 if it is below 60mmHg. these glomus cells send a signal via the glossopharyngeal nerve (carotid artery) or vagus nerve (aortic body) to the medulla respiratory centers. The chemoreceptors cause K+ leak channels to close, cell depolarizes, causes voltage gated Ca channels to come in, causes release of NT to the nerurons
