why and how does our brain trigger flight, fight, or freeze responses to our adrenal glands and body??

Question: why and how does our brain trigger flight, fight, or freeze responses to our adrenal glands and body??
- Keywords:
  adrenaline,
  fight or flight,
  reaction,
  response
Asked by Asiya A on 18 Mar 2025.
- Caroline Roche answered on 18 Mar 2025:
  
  These are survival mechanisms that are triggered when your brain perceives a threat or danger. Fight to confront the threat, flight to escape or freeze to try to avoid detection – they are automatic responses so they can go into affect before you need to think about it.
  A number of things happen within our bodies when it occurs. The bodies alarm system, the amygdala, within the brain is what detects the threat. It sends that information via the brains neural network to the hypothalamus. This kicks in to setup the body’s response, sending signals via the nervous system to the adrenal glands to release adrenaline and cortisol into the body. These then prime the body for action.

Question: why and how does our brain trigger flight, fight, or freeze responses to our adrenal glands and body??