🗻 Big Picture: Breathing (or ventilation) is the act of moving air into and out of your lungs to exchange carbon dioxide and oxygen. It's regulated by the medulla oblongata which controls the contractions of your diaphragm by sending signals through the autonomic nervous system to control blood carbon dioxide levels. Read on in this study guide to learn more!
What are you so good at that you can do it without even trying? A perfect omelette flip? Playing croquet? Hitting the high note in All I Want For Christmas Is You? We’re sure there’s something, but if not, we have one for you–breathing! It might be a little bit of a stretch because you’re not really doing it, it just sort of happens. At least it seems that way sometimes, but when it comes to our bodies, nothing just happens–something has to make things happen. Let’s find out what that something is below.
You’re probably pretty good at breathing by now (we hope), but we’re going to give you the rundown on how your body does it anyway. When you inhale, a broad muscle beneath your lungs called the Diaphragm contracts. This contraction causes your rib cage to expand and the contents of your abdomen to slide lower into your body, thus increasing the amount of space in your chest cavity.
All of this new space decreases the air pressure in your lungs, while the air pressure outside your body stays the same. Because air likes to move from a higher pressure environment to a lower pressure one, decreasing the pressure in your lungs causes air to rush in.
When the diaphragm releases, the reverse happens–your chest cavity shrinks, the air pressure in your lungs rises, and all of the air moves once again to the lower pressure environment, this time outside your body. See the 3D model above to visualize how your lungs expand and contract.
You might not be telling your diaphragm to contract all the time, but somebody is, and that somebody is your brain. It works with the Autonomic Nervous System which is in charge of all bodily activities that you do automatically, including regulating your heartbeat, digestive process, and of course, breathing (remember, autonomic → automatic).
The autonomic nervous system works by sending nerve signals to the diaphragm from the brain stem, which is constantly monitoring the CO2 levels in your blood. If that level rises too high, the brain tells the autonomic nerves to send more signals to the diaphragm, causing it to contract more frequently, and you to breathe faster. As your breathing increases, extra carbon dioxide is released into the atmosphere.
Eventually your blood CO2 levels will fall too low, at which point your brain stem tells the autonomic nervous system to put on the brakes, causing your breathing to slow the opposite process to occur. Keeping such close tabs on the amount of carbon dioxide in your blood makes sure that your pH stays within a restricted range, outside of which you would not be able to stay alive.
Breathing is important, but it’s not important enough to require your entire brain to make it happen. All of the orders that go to the autonomic nervous system come from the Medulla Oblongata, the main respiratory control center (also known as the respiratory rhythm center).
Adjacent to the control center is a chemosensitive region which is highly sensitive to CO2 and hydrogen ions. When these substances increase, it signals the control center to let it know it needs to change the pace of breathing. Both that region and the medulla are the ones pulling 24 hour shifts to send out the impulses that make your muscles contract and relax, so let’s give them a big thank you for doing most of our breathing for us.
So what have we learned today? We now know that breathing occurs due to contractions of the diaphragm that cause the air pressure in your lungs to go up and down, thus drawing in and releasing air. We know the medulla oblongata and its trusty chemoreceptive sidekick are behind it, paying close attention to your blood CO2 levels and sending signals through the autonomic nervous system to tell your diaphragm how fast or slow it should contract to compensate. Overall, you have a pretty good basic grasp on what breathing is and how it occurs. Well done!
1. What muscle contracts to make you inhale?
2. Why does air flow into your lungs when you breathe in?
When your diaphragm contracts, it increases the space in your chest cavity which lowers the air pressure in your lungs while the external pressure remains the same. Because air likes to move from high pressure environments to low pressure environments, air rushes into your lungs until the diaphragm relaxes again.
3. Where is the respiratory control center?
The medulla oblongata.
4. What is the purpose of the chemosensitive region by the medulla?
It’s purpose is to detect blood levels of CO2 to help the medulla control blood carbon dioxide levels.
5. How does the medulla send signals to the diaphragm?
Through the autonomic nervous system.
6.What functions does the autonomic nervous system control?
All bodily activities that occur automatically, including your heartbeat, digestive process, and breathing.
We hope you enjoyed studying this lesson and learned something cool about Breathing and its Regulation! Join our Discord community to get any questions you may have answered and to engage with other students just like you! Don't forget to download our App to experience our fun VR classrooms - we promise, it makes studying much more fun 😎