#1015 How do our hearts and lungs work automatically?

How do our hearts and lungs work automatically? We have an autonomic nervous system that makes organs like the heart and the lungs function automatically.

If you want to pick up a cup of tea, your brain has to go through several steps to accomplish the act. It has to make the decision to pick up the cup, it has to analyze the visual information to work out where the cup is, it has to command all of the relevant muscles to move to reach for the cup, grip the cup, lift the cup, then constantly monitor the signals from the muscles so that the cup is kept steady enough not to spill, then instruct the mouth to open, then drink and swallow, then return the cup to the desk. All of these steps require signals to and from the brain. The whole time you are drinking from your cup, your heart keeps beating and your diaphragm keeps your lungs filling and emptying.

There are two systems in our bodies. There is the one we can control and the one we can’t control. We can make our muscles move faster, but we can’t consciously make our hearts beat faster. We can move our eyes, but we can’t consciously lower our blood pressure. We can turn our heads, but we can’t slow down our digestion. We can sniff, but we can’t make ourselves stop sweating. Of each example I just gave, the first examples are the somatic nervous system. These are all of the systems in the body that you can control. The second examples are the autonomic nervous system, which are the things we cannot control.

The autonomous nervous system is split into two different types. There is the sympathetic nervous system and the parasympathetic nervous system. They both work autonomously. The difference is the sympathetic nervous system is concerned with fight or flight, while the parasympathetic system is concerned with rest and digest. They both control mainly the same organs, but in a different way. The parasympathetic system keeps the body running day by day. It makes the body rest and relax, it digests food and slows down the heart rate. The sympathetic system goes into action when we are under a stress response and it speeds up the heart, breathing rate, and blood pressure. We need both systems to be well balanced to be healthy. These systems work all the time, whether we are awake or asleep, and they keep the body in a state of homeostasis.

So, how do the heart and lungs work without the brain being involved. Well, you can breathe consciously, and many a meditation app will get you to do just that. However, generally, you don’t need to think about breathing. You can consciously hold your breath until you pass out, but once you are unconscious, you will start breathing again, automatically. You can also slow down your heart rate, if you can force yourself to relax, but that is more of a side effect of calming down than consciously changing your heart rate. Both of these processes happen without conscious thought, but that doesn’t mean the brain isn’t involved. The autonomous nervous system is connected to the hypothalamus and regulated by it. We can’t change our heart beat, but the hypothalamus can. It reacts to stimuli that are coming in from all over the body. If your blood pressure is too high or too low, the hypothalamus will receive that information and instruct the heart to speed up or slow down, via the sympathetic or the parasympathetic nervous systems. If your body sends signals that there is too much CO2, or not enough CO2, the hypothalamus will instruct the lungs to speed up or slow down. This happens autonomously in that there is no decision making involved. It is an automatic process where if A happens the hypothalamus triggers B.

The heart is connected to the autonomous nervous system, but it has its own regulator. The heart has a group of cells called pacemaker cells. Their job is to create the electrical signal that crosses the heart and makes the muscles contract, about once every second. When the sympathetic and parasympathetic systems are in balance, your heart beats at an average of 60 times a second, without you having to think about it. However, if you start exercising, the hypothalamus receives feedback from different parts of the body to say that not enough energy and oxygen are getting through. This information causes the hypothalamus to release a signal down the sympathetic nervous system to make the pacemaker cells go faster. Once exercise has stopped and there is enough oxygen and energy, the hypothalamus will send a signal down the parasympathetic nervous system telling the pacemaker cells to slow down again. The heart and lungs don’t work without the brain, but they do work without the conscious part of the brain. And this is what I learned today.

Photo by Monstera Production: https://www.pexels.com/photo/paper-hearts-of-different-size-pinned-on-pink-surface-5874612/

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