Ever wonder why you breathe faster when you're reading a suspenseful novel? Or why you sweat while checking the basement for that "strange noise"?
It's all due your sympathetic nervous system! When you feel a threat, your body does amazing things to prepare you to be able to engage in battle ("fight") or run away ("flee"). Your endocrine glands release neurotransmitters such as adrenaline, noradrenaline, and cortisol into your system, causing:
1. your pupils to dilate and your senses to heighten so you can easily scan the scene and recognize danger.
2. your heart to beat faster, the blood vessels to constrict in your extremities, and you to breathe faster so you get more blood and oxygen to your core muscles and they can act quickly.
3. your metabolism to speed up so it absorbs every bit of sugar and fatty acids to use as energy.
4. your perception of pain to decrease so even if you get injured you can continue to fight or flee.
5. you to begin to sweat so your body doesn't overheat in action.
6. your body hairs to stand on end so that you appear larger and more intimidating to enemies.
However, when there is not an actual threat of danger, like when you're watching a scary movie, your body can react like there is a real threat. These natural reactions can then present themselves as a loud heartbeat, hyperventilation, a tightening in your chest, icy hands or feet, cold sweats, goosebumps, or an upset stomach. You also can feel jumpy, sensitive to little sounds, and "paranoid".
But don't worry, it's just your body doing its job! It you needed to run away from a bear, for example, you would be pleased that your body can work in this extraordinary way! Some people actually like the way the adrenaline feels pumping through their systems. :)