what causes people to get squeamish ?

why do certain people (as myself) feel a certain feeling a intense
weakness when hearing about or seeing things like blood, human
anatomy, and cuts and gashes? why does it cause me to feel weak?
one thing i noticed i feel when i start to feel squeamish is i feel a funny
feeling in my feet, hands, & legs. i’m not sure what it is but they feel extremely weak and rich. why is this ?