The Neurobiology of Stress AKA How Stress Works
Have you ever had that experience where you zoom out and look at the situation you’re feeling stressed about and realize that in the grand scheme of things it probably doesn’t matter that much…? And, even though you can see that, you still feel stressed?
You’re not alone in this, and that is what we plan to cover in this blog. In this blog we will be offering information on what is happening in your brain and nervous system that keeps your body in a reactive, stressed-out state even though you logically realize you don’t need to be so stressed. We hope by sharing this information you can use it as a tool the next time you’re stressed to support your brain and nervous system in coming back to a regulated, balanced state more quickly.
The Stress Response
When faced with a stressor–whether it’s a looming work deadline, an unexpected bill, or a dangerous situation–the limbic system in your brain and your autonomic nervous system instinctually kick in.
This rapid response is often referred to as “a stress response” which can look like fighting, fleeing, freezing, fawning or flopping. All are built-in survival mechanisms that prepare you to get through and survive the threat (the stressor).
The Role of the Amygdala: The Brain’s Smoke Detector
This stress response process is incredibly fast, but it starts with the amygdala. The amygdala is an almond sized structure in the human brain responsible for scanning a person’s internal and external environment for potential threats to safety. When the amygdala detects a stressor and perceives it as a threat, it sends an alert to other parts of the brain.
The Hypothalamus: Command Center of the Stress Response
The amygdala signals the hypothalamus, a small but crucial area at the base of the brain that functions as the command center for your autonomic nervous system. The hypothalamus initiates the stress response by communicating with the sympathetic nervous system (one of the branches of the autonomic nervous system), which controls involuntary bodily functions such as heart rate and respiration.
Activation of the Sympathetic Nervous System: Rapid Physiological Changes
Once the hypothalamus activates the sympathetic nervous system, the body undergoes immediate physiological changes to prepare for action. This process, known as the acute stress response, includes:
Increased heart rate - blood pumps faster to supply muscles with more oxygen
Muscle tension - due to the increased blood flow and oxygen in the muscles tension builds so you have the strength or power needed to confront or get away from the stressor
Faster breathing - more oxygen enters the lungs, providing the body with additional energy
Release of epinephrine (adrenaline) - the adrenal glands release this hormone which increases alertness, sharpens focus and boosts energy
Pupil dilation - vision sharpens and narrows to better assess the environment
All these changes happen within seconds of encountering a stressor, priming your body to react swiftly.
The HPA Axis: Longer-Term Stress
If the stressor persists, the brain activates the hypothalamic-pituitary-adrenal axis (HPA axis), a more prolonged response system that helps sustain the body’s readiness for action.
Hypothalamus Signals the Pituitary Gland
The hypothalamus releases corticotropin-releasing hormone (CRH), which travels to the pituitary gland. In response, the pituitary gland releases adrenocorticotropic hormone (ACTH) into the bloodstream.
ACTH Stimulates the Adrenal Glands
ACTH travels to the adrenal glands, located above the kidneys, prompting them to release cortisol, often referred to as the “stress hormone”. Cortisol has several critical functions during a stressor, including:
Maintaining Energy Supply - By raising glucose levels in the bloodstream, cortisol ensures that muscles and the brain have enough fuel to handle the stressor.
This increase of glucose levels in the bloodstream for prolonged periods of time is what contributes to “cortisol belly”, or weight gain, amongst other physical health issues like chronic inflammation/pain, insulin resistance and diabetes.
Suppressing Non-Essential Functions - Cortisol temporarily dampens systems like digestion, reproduction, and immune response, allowing the body to focus its resources on the immediate threat.
This is why we tend to get sick if we’ve been stressed for an extended period of time, and also why long-term stress leads to gut issues.
Chronic Stress and Its Effects
While this stress response system is designed to protect you in the short-term, problems arise when stress becomes chronic. Chronic stress is when the body remains in a prolonged state of alertness and because it’s stuck in this state damaging effects on mental and physical health occur.
Impact on the Hippocampus
The hippocampus, a brain region essential for learning and memory, is particularly sensitive to cortisol. Chronic stress and elevated cortisol levels can shrink the hippocampus over time, leading to:
Memory problems
Difficulty concentrating
Increased risk of anxiety, depression, PTSD
Overactivation of the Amygdala
Prolonged exposure to stress can cause the amygdala to become hyperactive, making people more sensitive to perceived threats. This heightened state of alert can contribute to feelings of chronic anxiety, hypervigilance, irritability, anger and rage.
Suppression of the Prefrontal Cortex
The prefrontal cortex is responsible for rational decision-making and regulating emotions. Chronic stress can impair the function of this brain region, making it harder to think clearly, regulate emotions, or make thoughtful decisions.
The Parasympathetic Nervous System
Once the stressor is removed, the parasympathetic nervous system is activated, often referred to as the “rest and digest” system. This system works to counteract the effects of the stress response by:
Slowing the heart rate
Decreasing blood pressure
Resuming normal digestion and other bodily functions
The parasympathetic nervous system helps the body return to its baseline state, allowing for recovery and balance after the stressor has passed. In a healthy environment the sympathetic and parasympathetic branches of the autonomic nervous system work in tandem. The sympathetic branch activates in response to an acute stressor, the stressor is faced and resolved and the parasympathetic branch comes in and returns the inner system to homeostasis.
However, in situations of episodic, chronic and/or traumatic stress, the sympathetic branch gets stuck in the “on” position until there is no more energy to sustain the activation of the sympathetic branch and then the inner system shuts down into a collapsed state with little to no energy i.e “conservation mode”. Once some energy is restored in the person’s system, then we, as holistic therapists, often see a bouncing back and forth between an over-activated state and an under-activated state until we are able to lend the brain and nervous system some support with regulation and processing of the unresolved emotions and/or trauma.
Conclusion: Managing Stress for Better Health and Well-Being
The stress response is a powerful tool that we need for survival. But, when it’s activated too often or for too long, it can take a serious toll on the mind, body and soul. By understanding the neurobiology of stress–how the brain and nervous system react to stressors–we can better appreciate the importance of stress management techniques. Practices such as mindfulness, intentional movement, regular exercise, breathwork and regular relaxation can help regulate the body’s stress response, ensuring that it is used when needed but not causing long-term harm to your mind, body and soul.
If you’re curious to know more about different tools and strategies to regulate your stress responses, stay tuned! Our next blog will cover various somatic and holistic strategies that are effective at regulating the brain and nervous system, as well as, methods to heal unresolved pain and wounding that are likely at the root of chronic stress within the body.