Fear is a series of reactions in the brain triggered by a stressful stimulus and ending with such physical reactions as tense muscles, rapid heartbeat and rushed breathing. This is the well-known fight-or-flight response. Examples of fear stimuli include stage fright, spiders, seeing someone attacking with a knife or the sound of the front door suddenly banging open. Although many areas in the brain are at least partially involved in the fear response, research has shown which parts play major roles:
- Thalamus: determines where to send incoming data from the five senses
- Sensory cortex: interprets the data
- Hippocampus: stores and recovers cognitive memories, processes stimuli to ascertain their context
- Amygdala: interprets emotions, discovers possible threats, stores memories of past fears
- Hypothalamus: activates the fight-or-flight response when necessary
The brain uses two simultaneous processes to create a fear response, the "low road" and the "high road." The low road is reactive; it initiates a fight-or-flight response even before the nature of the stimulus is known. The high road is calmer and more thought-oriented. Here the brain analyzes the stimulus and compares it with other incoming data, such as sights and sounds, as well as memories of similar events; it then determines if the threat is real. The high road takes a bit longer than the low road, which is why an unexpected event like wind blowing the front door open first causes a moment of fear before calm sets in.
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