These responses include release of adrenaline, increased heart rate, changes in breathing, hypervigilance to possible danger, tunnel vision, and a host of other perceptual changes. You feel this as a whoosh of fear or terror. The alarm response is centered in the amygdala, which consists of two walnut-sized structures in your brain. The amygdala can be either on or off: it either triggers the alarm response or it doesn’t.
