How can the sight of blood cause someone to pass out?

Question

I understand that loss of blood pressure and oxygen to the brain can cause one to pass out, but how can the sight of something like blood cause it?

In: Biology

Answer 1

Vagus nerve over-stimulation: the nerve responsible for fight or flight sometimes over-does the response in people with true phobias. This causes a massive surge in blood flooding the body to ensure all your muscles and organs are ready for “go” that the brain gets left out. Loss of blood to the brain = loss of consciousness