Stress. Cortisol, as it is more scientifically known, is released when we are feeling anxious or under pressure. It is the ultimate marker of the body’s reaction to a challenge and has both biological and physiological symptoms.
A little on the physiology of stress…
There are two main stress response systems in the body: the sympathetic nervous system (SNS) and the as well as your HPA axis (read: hypothalamus, pituitary gland and adrenal glands).
The initial stress reaction and response…
Upon exposure to a stressor, our body judges whether or not is worthy of a stress response. This is done in the brain via two main ways; our sensory input (such as the things we may see, smell, touch, hear) as well as our emotional processing (does this situation or stressor evoke certain memories, thoughts or concerns?). The amygdala, is the area of the brain that is responsible for this emotional processing. It works to interpret our sensory input and if the situation is judged as stressful, the amygdala will send a distress signal to the hypothalamus which will in turn activate it.
Then the SNS kicks in…
The hypothalamus works much like a command centre, signalling to the rest of the body via the autonomic nervous system – AKA it is the primary driver of the overall stress response. The autonomic nervous system controls many involuntary body functions such as heartbeat, blood pressure and breathing and has two components: the sympathetic nervous system and the parasympathetic nervous system (PSNS). The SNS response exerts the rapid effect that we have come to know as ‘fight-or-flight’ mode and it can be likened to the accelerator in a car. In any situation where we are in fight or flight mode, the body releases the hormone epinephrine (adrenaline) in the periphery and acts to increase heartbeat, pushing more blood to the muscles, the heart and other vital organs as well as increasing pulse rate, blood pressure and rate of breathing. Epinephrine also triggers the release of glucose and fats from storage sites in the body, supplying energy at a time of need. Fight-or-flight mode also works in favour of our muscles, making us sweat more in order to dissipate heat in order for more efficient muscle action as well as constricting the blood vessels in our gastrointestinal tract and skin, slowing our digestion and helping make more blood available for muscle action.
During this time, the hypothalamus also releases corticotropin-releasing-hormone (CRH), which travels via the pituitary gland, triggering the release of adrenocorticotropic hormone (ACTH). ACTH travels to the adrenal glands where it prompts the release of cortisol from the adrenal glands, allowing the body to maintain a state of high alert. Cortisol also enables the body to maintain a steady blood glucose level by releasing stored glucose and fatty acids from the liver (for use as energy) so that the we can best cope with a prolonged stressor and return to normal when needed.
Usually, the hypothalamic response between the amygdala and the hypothalamus kicks in so quickly, most often before any visual cues of the pending situation, that the individual has no time to register it is even happening. Hence, for example, that is why people tend to jump out of the way of an oncoming car, before they can even register what is happening.
Once the initial surge of epinephrine subsides, there are two options…
Once the threat subsides, cortisol levels begin to fall and then the PSNS, which can be likened to the brake in a car, kicks in promoting the vegetative-like functions of ‘rest and digest’, calming the body after the danger has passed and bringing it back into a balanced state. Blood pressure and heart rate begin to normalise as well as normal body functions such as digestion and absorption, which were put on hold during fight-or-flight mode. During this time, the body is still on alert for a while, whilst it works to repair itself until everything re-enters into the pre-stress state.
The HPA axis’ primary function is to release glucocorticoids that activate a short-term physiological stress response. However, of stress persists, as such, it becomes chronic, the body adapts to a state of high alert and the communication between the HPA axis and other working systems of the body can become impaired. This makes it harder for the body to cope and therefore, predisposes one to issues such as weight gain, hormonal imbalance, mental health conditions, metabolic conditions, compromised immunity and more. In other words, chronic stress or chronically high levels of stress hormones can manifest in the overall decline in one’s mental and physical fitness and immune health.
Key takeways…
The stress response has two pathways – the autonomic nervous system adn the HPA axis. The autonomic nervous system has two parts: the sympathetic and the parasympathetic.
The autonomic nervous system controls more short-term stress responses though the efficient fighting action of the SNS and the calming action of the PSNS, whilst chronic and more adaptive stress tends to be implicated via the HPA axis (hypothalamic-pituitary-adrenocorticotropic axis).
The hypothalamus is the primary driver of the stress response.
Stress is nor good or bad, it is an innate physiological response. It is how we manage it that is key.
Read this post on how to reduce stress naturally.
References and for more on this topic:
Effects of stress on immune function: the good, the bad, and the beautiful
Hormones, stress and cognition: The effects of glucocorticoids and oxytocin on memory
Chronic stress and the HPA axis
As always, I would love to know your biggest takeaway and tell me what you do for stress management and relief – Tag us on Instagram @optima_health or #optimahealth.
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