The correct answer is sympathetic nervous system.
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The sympathetic nervous system is a component of the autonomic nervous system, together with the parasympathetic system. Their functions are opposite but coordinate to maintain homeostasis. The sympathetic system has a role to control the body's response during perceived threat (fight and flight reactions). According to this, it dilates the pupils, contracts the muscles, increases heart rate...</span>
Gravity, if it isn't and answer please comment back and tell me
It's mutualism cause both are getting something out of it