In modern times, however, bodily responses to fear can be detrimental, especially since the most important one is a negative one: the brain basically shuts down as the body prepares for action. The cerebral cortex, the brain's center for reasoning and judgment, is the area that becomes impaired when the amygdala senses fear. The ability to think and reason decreases as time goes on, so thinking about the next best move in a crisis can be a hard thing to do. Some people even experience feelings of time slowing down, tunnel vision, or feeling like what is happening is not real. These dissociative symptoms can make it hard to stay grounded and logical in a dangerous situation. Essentially, the body's response to fear or stress can be stressful in itself.
Fear is an emotion we all experience at one time or another, and its effects are important to understand when talking about disasters. As soon as you feel fear, the amygdala (a small almond-shaped organ in the center of your brain) sends signals to your autonomic nervous system (ANS), which then has a wide range of effects. The ANS kicks in, and suddenly, your heart rate increases, your blood pressure goes up, your breathing gets quicker, and stress hormones such as adrenaline and cortisol are released. The blood flows away from the heart and out towards the extremities, preparing the arms and legs for action. These effects served us well millennia ago, in situations where we were faced with beastly animals that thought they had found dinner.