How Does Your Body Control Things You Don’t Think About?
Your nervous system handles it without involving conscious thought. Information is constantly moving between your brain and body, so your body can react to what’s happening without waiting for you to notice it first.
If something suddenly startles you, for example, your heart may speed up, your breathing may shift, and your pupils may widen before you’ve really had time to think about what happened. You didn’t tell any of those things to happen.
Your Body Responds Without Waiting for You
Your nervous system is getting information from inside your body all the time, including things you aren’t aware of. It can detect your blood pressure, body temperature, and the levels of oxygen and carbon dioxide in your blood.
Take your heart. It doesn’t beat at exactly the same rate when you’re asleep, sitting at a desk, and moving around. It speeds up or slows down depending on what your body needs, and you don’t have to keep track of any of it.
The autonomic nervous system handles much of this work. It adjusts things like your heart rate, blood pressure, sweating, digestion, and pupil size without you having to think about them. If you’re getting hot, you don’t have to realize it and decide it’s time to sweat. Walk into bright light and your pupils get smaller on their own.
Some Automatic Things Can Still Be Controlled
Breathing is a little different. You can go hours without giving a single breath any thought, even while you’re asleep, but you can also decide right now to hold your breath or take a deep one. So breathing works both ways. Your body normally takes care of it, but you can temporarily take over.
You don’t get that same control over everything. You can’t decide to make your pupils a little smaller or directly tell your digestive system to move food along.
Most of this happens without ever becoming a conscious decision. Sometimes you only notice the result: your heart is suddenly beating faster, you’ve started sweating, or your eyes have already adjusted to the light. Your body didn’t need to get your attention first.