It's dark out, and you're home alone. The house is quiet other than the sound of the show you're watching on TV. You see it and hear it at the same time: The front door is suddenly thrown against the door frame.
Your breathing speeds up. Your heart races. Your muscles tighten.
A split second later, you know it's the wind. No one is trying to get into your home.
For a split second, you were so afraid that you reacted as if your life were in danger, your body initiating the fight-or-flight response that is critical to any animal's survival. But really, there was no danger at all. What happened to cause such an intense reaction? What exactly is fear? In this article, we'll examine the psychological and physical properties of fear, find out what causes a fear response and look at some ways you can defeat it.
The brain is a profoundly complex organ. More than 100 billion nerve cells comprise an intricate network of communications that is the starting point of everything we sense, think and do. Some of these communications lead to conscious thought and action, while others produce autonomic responses. The fear response is almost entirely autonomic: We don't consciously trigger it or even know what's going on until it has run its course.
Because cells in the brain are constantly transferring information and triggering responses, there are dozens of areas of the brain at least peripherally involved in fear. But research has discovered that certain parts of the brain play central roles in the process:
When the hypothalamus tells the sympathetic nervous system to kick into gear, the overall effect is that the body speeds up, tenses up and becomes generally very alert. If there's a burglar at the door, you're going to have to take action -- and fast. The sympathetic nervous system sends out impulses to glands and smooth muscles and tells the adrenal medulla to release epinephrine (adrenaline) and norepinephrine (noradrenaline) into the bloodstream. These "stress hormones" cause several changes in the body, including an increase in heart rate and blood pressure.
At the same time, the hypothalamus releases corticotropin-releasing factor (CRF) into the pituitary gland, activating the adrenal-cortical system. The pituitary gland (a major endocrine gland) secretes the hormone ACTH (adrenocorticotropic hormone). ACTH moves through the bloodstream and ultimately arrives at the adrenal cortex, where it activates the release of approximately 30 different hormones that get the body prepared to deal with a threat.
The sudden flood of epinephrine, norepinephrine and dozens of other hormones causes changes in the body that include:
Your breathing speeds up. Your heart races. Your muscles tighten.
A split second later, you know it's the wind. No one is trying to get into your home.
For a split second, you were so afraid that you reacted as if your life were in danger, your body initiating the fight-or-flight response that is critical to any animal's survival. But really, there was no danger at all. What happened to cause such an intense reaction? What exactly is fear? In this article, we'll examine the psychological and physical properties of fear, find out what causes a fear response and look at some ways you can defeat it.
What is Fear?
Fear is a chain reaction in the brain that starts with a stressful stimulus and ends with the release of chemicals that cause a racing heart, fast breathing and energized muscles, among other things, also known as the fight-or-flight response. The stimulus could be a spider, a knife at your throat, an auditorium full of people waiting for you to speak or the sudden thud of your front door against the door frame. The brain is a profoundly complex organ. More than 100 billion nerve cells comprise an intricate network of communications that is the starting point of everything we sense, think and do. Some of these communications lead to conscious thought and action, while others produce autonomic responses. The fear response is almost entirely autonomic: We don't consciously trigger it or even know what's going on until it has run its course.
Because cells in the brain are constantly transferring information and triggering responses, there are dozens of areas of the brain at least peripherally involved in fear. But research has discovered that certain parts of the brain play central roles in the process:
- Thalamus - decides where to send incoming sensory data (from eyes, ears, mouth, skin)
- Sensory cortex - interprets sensory data
- Hippocampus - stores and retrieves conscious memories; processes sets of stimuli to establish context
- Amygdala - decodes emotions; determines possible threat; stores fear memories
- Hypothalamus - activates "fight or flight" response
Fight or Flight
To produce the fight-or-flight response, the hypothalamus activates two systems: the sympathetic nervous system and the adrenal-cortical system. The sympathetic nervous system uses nerve pathways to initiate reactions in the body, and the adrenal-cortical system uses the bloodstream. The combined effects of these two systems are the fight-or-flight response.When the hypothalamus tells the sympathetic nervous system to kick into gear, the overall effect is that the body speeds up, tenses up and becomes generally very alert. If there's a burglar at the door, you're going to have to take action -- and fast. The sympathetic nervous system sends out impulses to glands and smooth muscles and tells the adrenal medulla to release epinephrine (adrenaline) and norepinephrine (noradrenaline) into the bloodstream. These "stress hormones" cause several changes in the body, including an increase in heart rate and blood pressure.
At the same time, the hypothalamus releases corticotropin-releasing factor (CRF) into the pituitary gland, activating the adrenal-cortical system. The pituitary gland (a major endocrine gland) secretes the hormone ACTH (adrenocorticotropic hormone). ACTH moves through the bloodstream and ultimately arrives at the adrenal cortex, where it activates the release of approximately 30 different hormones that get the body prepared to deal with a threat.
The sudden flood of epinephrine, norepinephrine and dozens of other hormones causes changes in the body that include:
- heart rate and blood pressure increase
- pupils dilate to take in as much light as possible
- veins in skin constrict to send more blood to major muscle groups (responsible for the "chill" sometimes associated with fear -- less blood in the skin to keep it warm)
- blood-glucose level increases
- muscles tense up, energized by adrenaline and glucose (responsible for goose bumps -- when tiny muscles attached to each hair on surface of skin tense up, the hairs are forced upright, pulling skin with them)
- smooth muscle relaxes in order to allow more oxygen into the lungs
- nonessential systems (like digestion and immune system) shut down to allow more energy for emergency functions
- trouble focusing on small tasks (brain is directed to focus only on big picture in order to determine where threat is coming from)
0 comments:
Post a Comment