Some students will have difficulty with Figures 36.12 and 36.13. Be certain you yourself understand what is happening before you begin explaining it. If the chemistry is beyond your course objectives, modify your requirements but do not skimp on the basic concept. So often students do not understand what is happening. Keep in mind that everything happens by diffusion.
Every action is a passive movement toward equilibrium.
It is usually a real revelation when students realize that the control of respiration has to do with the carbon dioxide level rather than the oxygen level. Fortunately, this is not a difficult mind-set to alter. There is a great deal you can do with this section on the unhealthy respiratory system. I caution you, however, not to be morbid or preachy. Rather, present facts and encourage your students to look for reasons behind situations.