The sympathetic nervous system is your “survival mode.”
Let’s say you’re walking down the street and you see a raging dog. Your natural reaction is to turn and run! This running takes a lot of energy.
At that moment you would want your body to focus its energy on your muscles and respiratory system, rather than your digestion and blood pressure. That is the sympathetic nervous system. This states detects the threat through your five senses and puts your body in survival mode. Your body would then be focusing all of its resources on you running away.
When your sympathetic nervous system is stimulated, your digestion is inhibited.
The parasympathetic nervous system does the opposite. The parasympathetic nervous system is your body’s “recovery mode.” When your body doesn’t detect danger, you can relax and your parasympathetic nervous system is stimulated. This slows down the heart rate, stimulates digestion, as well as liver, bladder, and kidney function. The body begins to restore itself.