Turning off stress:
http://ncu9nc.blogspot.com/2018/04/the-parasympathetic-nervous-system-and.html
Turning Off Stress: The Parasympathetic Nervous System And Spiritual Development
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The sympathetic nervous system is involved in producing the body's response to stress. The parasympathetic nervous system is involved in turning off the body's response to stress.
Anything that activates the parasympathetic nervous system suppresses the sympathetic nervous system and helps you to relax.
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Learning to turn off stress is also helpful in spiritual development because when you are stressed, you are more likely to be thinking about yourself and your problems ie. being egocentric. But when you are relaxed, you are less likely to be thinking about yourself and more likely to be in harmony with spiritual values like love, kindness, forgiveness, tolerance etc.
While I agree with that in one way, I feel the way you express this sounds remarkably materialist - which I am pretty sure you aren't!
For example, one reads that one of the amigdala processes fear. Compartmentalising the brain's function in that way can make one think of a machine where different bits have different functions. However, consider how a fear centre might really work - what does it actually do?
Well if I saw a tiger racing towards me, I'd be very fearful.
However if I was in a zoo, and there was a suitable fence, I'd just marvel at the power of the beast.
However, if I knew that there was a dispute about whether the fencing was adequate, I might feel fear once more.
If I wasn't in a zoo, and had a gun, and knew how to use it, I might feel sorrow because I would be safe but have to kill the creature.
What I am getting at, is that the fear centre would have to call on the whole of the rest of the mind in order to even determine if fear was an appropriate response!
This observation seems to generalise - specifying that any portion of the mind/brain - a hormone, a 'component' of the brain, or the parasympathetic nervous system performs some role, inevitably pulls in the rest of the mind!
David