What happens when you come into a clearing in the woods and see a bear? Your heart thumps, face flushes with increased bloodflow, muscles tense, and breathing quickens. “When danger nears, the hypothalamus (the same part of our brain that regulates body temperature) “flips a switch.” Before we have time to think, our brain speeds ahead of us, ordering the release of appropriate chemicals. Our brain also increases blood flow to the muscles, allowing for quick action. Breathing deepens to elevate oxygen intake. Heart rate and pressure increase to speed oxygen delivery. Many nonvital systems temporarily shut down. Growth, digestion, and the immune system stop functioning so that energy is not wasted on systems not required for immediate survival. But the brain acts differently if the danger is farther away. According to one study, the distance of the threat relates to the area our brain uses to face it. If the angry mother bear appears far away, the part of our brain used for strategy (called the ventromedial prefrontal cortex) activates. But as she draws closer, the focus switches to the fight or flight part of our brain, known as the periaqueductal gray.” God designed the human brain to be marvelously adaptive for every survival situation. We are indeed “fearfully and wonderfully made,” as the Bible says.
The Human Body—Wired for Extremes by Heather M. Brinson Answers in Genesis Sept. 1, 2009