Stress, a supposedly harmful thing from which all of us suffer multiple times in our lives – and all of us also listen multiple pieces of advice to avoid it in our lives. Still, for most of us it becomes nearly impossible to keep stress away. Why is it so? Why can’t we bypass stress completely? The answer lies in how our brain reacts to stress and in this article we’ll try to understand it.
The Stress Response: How Our Brain Reacts In Stressful Conditions
You might have experienced it already: when something stressful happens, a variety of physical and psychological changes take place in your body even before you think about them.
• Heart beats become faster
• Breathes become heavier
• Beads of sweat start appearing on forehead and other parts of body
• Muscles become tense
• And so on…
Depending on the severity of condition, the number and severity of these symptoms may vary. The more life-threatening the condition you’re facing, the more of these changes take place in your body. But how and why these changes appear has a very amazing process underneath, which can blow your mind. Are you ready to explore it?
Okay, let’s get started. Just like most other things in human body, the stress response begins in brain. You may know already that our eyes and ears both send the image and sounds they see and hear to brain for processing. So whenever an image or sound related to any dangerous event is sent for processing to amygdala (the part of brain responsible for processing of emotions), it interprets them and sends a distress signal to hypothalamus, which is basically the command center of brain.
This command center communicates with whole body through the wiring of nervous system to control a variety of activities like breathing, rate and momentum of heartbeat, blood pressure, constriction of blood vessels and many other activities. To take it a step further, there’re two separate components in nervous system as well:
• Sympathetic Nervous System: This system activates the so called “fight-or-flight” response and provides a burst of energy to our body to combat or run away from the dangerous situation – much like the gas pedal of a car.
• Parasympathetic nervous system:This system acts like a brake and calms down the body after the danger has passed.
So whenever amygdala passes a distress signal to hypothalamus, it activates the sympathetic nervous system by sending signals to adrenal glands through autonomic nervous system. In response, these glands start pumping adrenaline hormone into blood. As adrenaline circulates through blood, a number of psychological and physical changes start taking place. Heart beats become faster as heart starts pumping more blood to muscles and other vital organs for taking required actions faster and harder. As a result of this increased blood flow, pulse rate and blood pressure suddenly go up.
The person also starts breathing heavily as small airways going to lungs spread wider to supply as much oxygen as needed to lungs. Extra oxygen is then sent to brain for increasing alertness, due to which sight, hearing and other sensory perceptions become sharper. In the meantime adrenaline also floods nutrients like sugar (glucose), carbohydrates and fat from temporary storage sites into bloodstream to provide much needed energy for executing the required extraordinary tasks.
Sounds interesting, isn’t it? But here’s an even more interesting things that’ll completely blow your mind: All these things happen in less than a split second that we don’t even become aware of them. The wiring between amygdala and hypothalamus is so strong that hypothalamus sends the distress signal to sympathetic nervous system even before the image processing completes in amygdala.
That’s why we jump out of the path of an overcoming vehicle without even realizing what we’re doing!
Now that was the story for a sudden life-threatening kind of stress, like danger of suffering an accident on road. What if a person continues to sense the danger for a long time (i.e. financial instability, family reasons or the risk of losing job etc.)? Well, in that case an additional part of stress response system comes into play: the HPA axis.
The job of HPA axis not a separate part actually – it’s a complete system made of three different parts. Its job is to keep the sympathetic nervous system activated until the danger situation passes. It basically consists of three parts: the hypothalamus, pituitary gland and adrenal glands. As initial surge of adrenaline subsides, the hypothalamus part of HPA axis releases another corticotropin-releasing hormone (CRH) that travelles to pituitary gland and triggers the release of an additional adrenocorticotropic (ACTH) hormone.
This hormone then travels to adrenal glands, triggering them to release cortisol. The physical and emotional state of a person stays rewed up and alert until this cortisol thing is released into the blood. As soon as danger situation passes, the cortisol levels fall. And then begins the job of parasympathetic nervous system to dampen the state of stress response.