The amygdala will release a neurotransmitter compound called glutamate. This is the chemical compound behind fear that often occurs. Then there is a response coming from a part of the brain called periaqueductal gray. This is the part of the brain that regulates two forms of fear reactions such as jumping or creeping. Then, the hypothalamus is responsible for regulating resistance reactions which can then increase heart rate.
Fear also makes the body release glucose which is ready to be channeled into the blood. It is useful to give us strength to run if needed. Reactions Fear that occurs to everyone is different, according to the level of fear. Some just close their eyes or cover their ears, some are running.
actually the emotional response that comes with fear adds awareness and keeps the body and brain focused on threats. When Fears subside, the brain usually releases neurotransmitters and hormones that can make the body's system rest. "Heart rate drops, breathing slows down, creeps begin to subside.