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How does the brainstem work? More specifically, how does it regulate breathing? (question by EW)
The brainstem is pretty complex. If you are wondering where the brainstem is, think of the brain. Which part would you grab like the stem of the flower? That’s the brainstem. It comes down from the brain and goes into the spinal cord. It carries all the information from the brain to the rest of the body and then up from the body to the brain.
As for how breathing is regulated, there are special sensors detecting oxygenation in the blood. They do not measure oxygen directly, which you might think would make the most sense. Instead, they measure how much CO2 there is in the blood (the sign that oxygen has been used). They don’t even measure this directly, but measure pH. CO2 (carbon dioxide) is actually acidic, so these special detectors, known as chemoreceptors, detect the decrease in pH caused by increased levels of CO2 and therefore decreased oxygen. This happens in the carotid body (located in the carotid arteries in your neck) and these send projections back to the medulla oblongata in your brainstem. When the pH is getting too low, the medulla oblongata tells your lungs to work harder, and when pH is getting too high, it tells your lungs to relax.
