What happens in the brain during fight or flight

HostWe have all had that moment where our heart suddenly tries to jump out of our chest. Maybe a dog barks too loud or you trip on the stairs. It feels like your body takes over before you can even think about what's happening. What's the very first thing that happens in the brain when we feel that jolt of fear?

GuestIt happens fast because it has to. There's a tiny part of your brain called the amygdala. It's about the size of an almond and it sits deep inside. You can think of it as a smoke detector that never shuts off. Its only job is to watch for anything that might be a threat. The second it spots something scary, it sends a red alert to the rest of the brain. Hmm, it doesn't wait for you to look at the scene and decide if it's dangerous. It skips the thinking part of your brain entirely so it can save your life. If you had to stop and wonder if that sound in the brush was a lion or just the wind, you might not be around much longer. So, the amygdala just assumes it's a lion every time. It chooses being safe over being right.

HostSo it's kind of like a reflex. But how does that tiny almond-sized spot make my whole body feel like it's vibrating?

GuestWell, once that alarm goes off, it talks to a command center called the hypothalamus. This spot kicks your whole body into gear by dumping chemicals into your blood. You have probably felt the rush of adrenaline. That's the big one. It's like high-speed fuel for your muscles. It tells your heart to pump as fast as it can so your arms and legs have plenty of blood. It makes your lungs open wide to take in more air. It even tells your liver to dump extra sugar into your blood for a quick burst of energy. Think about your skin, too. You might get pale because the brain is pulling blood away from the surface and sending it deep into your muscles. It does this because if you get a scratch while you're running away, you'll bleed less. Your body is basically turning into a survival machine in less than a second.

HostBut if I'm just nervous about a job interview, I don't need my liver to dump sugar or my heart to race. It actually makes it harder to talk. Why can I not tell my brain that I'm safe?

GuestYeah, that's the tricky part. When the amygdala is in charge, it actually turns down the power to the part of your brain that handles logic. We call that part the prefrontal cortex. It lives right behind your forehead and it's the part of you that plans and stays calm. But that part is slow. In a real scare, being slow can be a big problem. So the brain dims the lights on your smart, logical side so it can focus all its power on survival. That's why you might stutter or forget your words when you're really stressed. Your brain has literally sidelined your ability to think clearly because it thinks you're in a fight for your life. Even your spit dries up. You get that dry mouth feeling because your body doesn't want to waste water on digesting your lunch when you're in a life-or-death moment. Every single drop of fluid and every bit of energy is redirected.

HostThat feels like a huge mistake for the world we live in now. Most of the things that stress us out today are things we need our smart brain for. We need to think to solve problems at work or fix a fight with a friend. Is our brain just stuck in the past?

GuestIn a way, yes. Our brains are using gear that was built for a much more dangerous world. Back then, a loud noise usually meant something was coming to eat you. Today, it might just be a loud truck. But the brain hasn't had time to catch up. It treats a mean text or a pile of bills the same way it would treat a wolf. This is why people feel so drained after a stressful day. Your body has been in high gear, ready to run a marathon, but you were just sitting in a chair. All that fuel and energy has nowhere to go, so it just sits there and makes you feel shaky and tense. If those chemicals like cortisol stay in your system for too long, they start to wear you down. It's like leaving a car engine revving in the driveway for hours. Eventually, the parts start to fail.

HostPeople always call it fight or flight, but I have had times where I just feel stuck. Like I can't move or even breathe for a second. Is that the alarm failing?

GuestNot at all. It's actually a third choice called the freeze response. Sometimes the brain decides that the best way to stay safe is to not be noticed at all. If you're totally still, a predator might miss you. Your muscles get tight, but you stay put. There's also a fourth one called fawning, where you try to be as nice as possible to the person who's scaring you to keep things from getting worse. The amygdala is just picking from a menu of survival tricks. It picks whatever it thinks will keep you alive based on what has worked for humans for a long time. Some experts are now looking at how this same system might even play a role in how we bond with others under pressure.

HostThe same alarm that kept us safe from lions is still ringing in our ears today when we hear a dog bark across the street.