Biologists organized the human body into different organ systems. You have a digestive system that breaks down and processes foods, a circulatory system that distributes blood to and from your organs, and a respiratory system that brings oxygen into your body and carbon dioxide out. Neuroscientists are most interested in the nervous system, which is the network of organs, nerves, and supportive systems that send and receive neural signals to and from various parts of the body. The nervous system links our experiences in the outside world with our actions and attitudes. It's main job is communication. If you think about it, your nervous system has a lot of work to do even when you're not doing a lot of work. Think of all the systems it has to regulate when you're just hanging out. It's even more complicated when there are lots of sensations around. One part of your nervous system is called the autonomic nervous system. This system controls your body internally. It carries information about the inside of your body to the central nervous system which is your brain and your spinal cord. The autonomic nervous system is responsible for the action of your organs, like your heart, and for regulating hormones. This system plays an essential role in keeping the body's internal environment imbalance, it also controls your temperature and blood sugar. It's a really complicated job. But everything isn't always a calm walk. Sometimes, your autonomic nervous system has to help recharge you or to get you ready for danger. It does this through two systems, the parasympathetic nervous system which calms you down and the sympathetic nervous system which regulates the fight, flight, or freeze response. The parasympathetic nervous system is the housekeeping division. It works on recovery from activities, it activates the stomach for digestion, slows the heart rate, and decreases blood pressure. If you're meditating or relaxing, you're activating your parasympathetic nervous system. But, what if you're not in a relaxing moment? What if you sense danger? What are your options? Well, one is to fight the danger and the other is to run away. The fight or flight response is a typical reaction shared by all animals in danger or in stressful situations. When your brain identifies stress, it prepares your body for vigorous activity and gets your body ready to handle the stress. Some people call this process the fight or flight response because two of the most obvious reactions to immediate dangers are to fight them or to run away from them. But there's a problem, because sometimes there's no one to fight and no place to run. In many cases, people just freeze because of this, some people now call it the fight, flee, or freeze response. Let's walk through how this works. Imagine you're in a scary place and you hear a noise, all the sudden your body fires up and your hands become cold and clammy. Your heart races, your blood pressure shoots up, well you can thank your sympathetic nervous system for that. When your stress response gears up, it activates certain physiological actions in your body's sympathetic nervous system to get you ready to fight the dangerous activity, flee from it, or freeze to avoid detection. It designed to mobilize your body as much as possible and help you survive. Here are just some of the things that are going on. You breathe more quickly to get oxygen moving around your body. Your heart rate increases to circulate the oxygen and at the same time, blood is diverted away from your digestive organs and the bladder relaxes. This might explain why we feel the need to go to the bathroom during stressful situations and why our stomach tends to feel queasy during these situations. Blood is diverted to the major muscle groups so we can fight or flee easier. Because blood is going to those major muscle groups it's pulled away from the extremities, which is why our hands feel cold during stress. So you're ready to face the challenge, run away from the challenge, or stay as still as possible.
