Physiology – Respiratory System 2 Practice Test

The key idea is how temperature changes shift the hemoglobin-oxygen dissociation curve. A leftward shift means hemoglobin has a higher affinity for oxygen at a given partial pressure of O2, so it holds onto O2 more tightly.

When the body is hypothermic, the cooler temperature increases hemoglobin’s affinity for O2, moving the curve to the left. This favors loading of O2 in the lungs (where PO2 is high) but makes unloading in tissues more difficult. Since metabolic demand is reduced in hypothermia, this reduced release is less problematic.

The other scenarios would push the curve the other way: higher temperature (hyperthermia) lowers O2 affinity, shifting the curve to the right; increased 2,3-DPG or acidosis also decrease Hb’s affinity for O2, causing a rightward shift.