The Brain on High Alert
Fear puts our brains on high alert—it puts us on guard. In psychology, the word for this high-alert state is hypervigilance.
Because the fearful brain is so preoccupied with protecting us from danger, it takes on an even stronger better-safe-than-sorry attitude than it normally would. The fearful brain would always rather err on the side of caution.
The problem is that when fear causes the brain to err on the side of caution, it becomes far more likely that neutral inputs will be mistaken for dangerous ones.
How Pain Works
All pain comes from the brain. If you touch a hot stove, sensory input will travel from your hand to your brain (Hot!), where your brain will interpret that sensory input (Danger!), and send a pain signal in response (Ouch!). Pain is the brain's way of alerting you to danger—in other words, pain is a danger signal.
Whenever you feel pain in the body, it's because specific nerve fibers in your brain have been activated. When you burn your hand, it feels like the pain is coming from your hand, but the sensation is actually coming from the part of your brain that makes you feel pain in your hand.
If a brain surgeon tickled that same part of your brain in just the right way, even in the absence of anything actually happening to your hand, you'd feel pain in your hand.
Even if someone has lost their hand to amputation, stimulating that same part of the brain will cause them to feel the very same hand pain. This is what we mean when we say that all pain comes from the brain.