• Jane Litsey

Demystifying the nervous system - part 2

How do the sympathetic and parasympathetic nervous system relate to the two highest priorities of any animal - survival and reproduction? If you think of which of the above two is the most important it becomes clear that if you don’t survive you cannot reproduce. So on some level, the nervous system evolved to value survival over reproduction.

So what threatens survival? If we look evolutionarily, threats included a deficiency of inputs like lack of food and essential nutrients, lack of warmth, lack of water, etc. – Or the threat was an attack from high levels predators or a neighboring group member.

What is the response of most animals to threat? The survival instinct historically was to move away from or attack the environment that was threatening survival. Move away from the predator, move away from the food desert, move away from the dry-waterless environment, move away from the darkness. Or attack the high-level predator or neighboring group member. The system that responds to threat is the sympathetic nervous system. It evolved to move the organism away from danger or attack the immediate threat to maintain survival.

You have felt the sympathetic nervous system when you are about to speak in front of a group and your palms begin sweating, your heart starts beating faster, your breathing speeds up and you notice tension in your body.

So how did we historically turn off the sympathetic nervous system? We found safety. In the form of a new food source, a new water source, sunlight, or we won the fight/outran the predator.

We could finally stop moving and relax when our life was no longer in danger. The side of the nervous system that activates with safety is called the parasympathetic nervous system. It turns on when our organism is digesting, resting, or relaxing. It is the state where the organisms feels safe and has its needs met.

You have felt the parasympathetic nervous system when you feel a sense of calm, peace or deep relaxation.

Because these movements were so important to survival of the organism and the promulgation of the species, the sympathetic and parasympathetic nervous system do not require conscious thought or action. They happen quickly and automatically - like a reflex – which is why together they are known as the autonomic (automatic) nervous system.

Are you with me still? Do we have any questions so far? I hope you are enjoying learning about yourself :)


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