Are you afraid of spiders? Many of us are, and when confronted with one, we’ll have one of two responses - the first is fight- to spring into action and show that spider who runs the jungle. The second is flight- to run away in fear. This human response to perceived threats is aptly named the fight-or-flight response, and is the result of an interaction between our brain and endocrine system, an interaction called the - you ready? - hypothalamic-pituitary-adrenal axis*. For brevity’s sake, we call it the HPA axis.