The parasympathetic system is the rest and digest, sleep, recuperate from injury, all the cool thing.
The sympathetic system comes entirely from neurons in the thoracic cord in our upper part of the body. The parasympathetic system gets its connections from two places. The cranium so these are coming out through cranial nerves. And then also from the sacral cord and so because of that, this is often called the cranio-sacral system. But let's take an example of how these two systems work in opposition. Let's look at the heart rate. The parasympathetics innervate the heart, and they drive heart rate down. The sympathetics innervate the heart and they drive heart rate up.
Throughout the day, we are in either one of these emotional states : Emotionally driven or resting and digesting. Moment to moment we are changing form one to another. Our sympathetic and parasympathetic states change across our life cycle. Have you noticed how children are always in a playful and jolly state - they are not worrying about their next meal or next paycheck. So young kids are very para-sympathetically dominated. Their job is to grow, their job is to absorb nutrients.They do not hold grudges, their anger lasts for a few minutes and they forget and move on with life. They are most of the time in parasympathetic mode. But as we go from being born to old age, we are moving in a steady direction towards a more sympathetically dominated state. This could be the cause of all the lifestyle diseases in old age. The sympathetic domination is going to drive up heart rate and it's going to drive up blood pressure. We hold on to thoughts, worry a lot and fail to enjoy the moment.
Now there are other conditions, which will bias an individual towards parasympathetic or sympathetic. For instance, very good aerobic athletes are very parasympathetic. In the old days in the Tour-de-France cyclists, they had resting heart rates of about 30 beats per minute. That’s very low. A normal individual at rest might have a heart rate at around 60 to 70. So that's very low. So parasympathetic domination is seen in athletes. When you are asleep, the body is in a relaxed state and there is a very low sympathetic tone. You wake up, a sympathetic tone automatically comes up.
To conclude, I would like to emphasize : Be happy, be forgiving, enjoy every moment and stop worrying. Be a child your entire life, we can't become an athlete overnight, but we can be more active and try to keep our heart rate low, be more relaxed and keep our parasympathetic system active. That could be a our wellness mantra.