Explore how CO₂-driven pH changes activate chemoreceptors and the medulla, which adjusts diaphragm and intercostal activity to control ventilation in IB Biology HL C3.1.15.
There is a relationship between form and function in the diversity of molecules and of systems.
Explain the causes of a decreased blood pH and its effects on the ventilation rate in humans.
a. increased (cellular) respiration can increase CO2 levels in blood
OR
anaerobic (cellular) respiration produces lactic acid;
b. due to exercise/lack of oxygen;
c. (aqueous) carbon dioxide reacts to form carbonic acid /H+ions (and HCO3−ions) OR
increased CO2 levels in blood cause a decrease in pH / acidosis
OR
lactic acid in blood can release H+ions / can cause a decrease in pH /acidosis;
d. in the presence of carbonic anhydrase (enzyme);
e. chemoreceptors detect levels of carbon dioxide (in the blood)
OR
chemoreceptors monitor (blood) pH/H+(in blood);
f. (chemoreceptors) found in aorta/carotid arteries;
g. (chemosensors/chemoreceptors) send information to respiratory centre in brain OR
to the medulla/brainstem;
h. (medulla) sends nervous impulses to the external intercostal muscles;
i. (medulla) sends nervous impulses to the diaphragm;
j. through intercostal/phrenic nerve;
k. increasing breathing/ventilation rate;
I. increasing volume of the lungs (during inhalation)/ increasing depth of breathing;
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