In a sudden catastrophic event or even in the case of minor stimuli from the environment that we interpret as a threat, and before we become fully aware of what is happening we are oftentimes ‘’abducted’’ by our amygdala, an almond-shaped nucleus located deep in the brain known as the center of fear, which takes the reins, sends a clear message about threats to the hypothalamus and our bodies are taken over by the ‘fight or flight reaction’ – the sympathetic nervous system is activated, the body is assaulted by a storm of adrenaline released from the adrenal glands, heart rate and arterial pressure rise, blood is directed to muscles, glucose and fat are mobilized into the bloodstream and carried by the bloodstream they reach the muscles to supply them with energy, all to enable an instantaneous escape from danger or a struggle for survival. Such a reaction is credited with fantastic urban legends of superhuman endeavors in hopeless situations that are unattainable under normal circumstances, such as lifting impossible burdens to save human life, and is more commonly known simply as stress. When the alarm phase or the first adrenaline wave passes, the hypothalamus mediates the adaptation phase via the hypothalamic-pituitary-adrenal axis – it releases cortisol to keep the body alert until the threat is completely gone. Depending on the nature of the threat and our individual abilities, the adaptation phase may last differently, and the levels of stress hormones circulating in the bloodstream may remain elevated for a long time and affect both physical and mental health, but what trace do they actually leave on our brains?
(Im) perfect storm or damage to the detriment of protection
Changes and demands of the environment are constantly present throughout everyday life. The brain plays a major role in interpreting the nature of these stimuli and accordingly orchestrates the physiological and behavioral adaptation of the human body. Physiological adaptation includes activation of the sympathetic and parasympathetic systems, the hypothalamic-pituitary-adrenal axis, the immune system, and metabolic and molecular processes within all organs in the body, and the body’s ability to achieve stability by activating and deactivating these systems is defined as allostasis. Physiological mechanisms in a healthy individual adapt easily and quickly to the requirements of the environment and are synchronously activated and, if necessary, inhibited. Frequent changes and excessive repetitive strengthenings and weakenings of responses in stressful situations gradually deplete the body and put it in a state of allostatic load, which can lead to excessive production of stress hormones and inability to silence the hypothalamic-pituitary-adrenal axis. The ability to adapt or trigger a stress response can also be altered due to genetic factors or previous life experiences.
In the eye of the storm is the brain, a biological organ whose molecular and neurochemical profile and its tissue architecture itself are constantly changing under the influence of acute and chronic stress.
The neurochemistry of stress and neuroplasticity
The complexity of human behavior depends on the organization of neurons into precise anatomical circuits – within the anatomical units of the brain nerve cells must be capable of reorganization that allows learning, memory and action in accordance with the requirements of the environment. The networks of neurons in the brain of a healthy individual are flexible and resilient, so they are remodeled according to experience and thus enable an appropriate response to similar situations in the future. Due to genetic factors or past experience, an individual’s brain may be less able to remodel and adapt and more prone to inappropriate reactions. Normal aging also involves a potentially reversible loss of resilience.
The discovery of glucocorticoid and mineralocorticoid receptors in the hippocampal formation, a region of the brain responsible for episodic and spatial memory and mood swings, paved the way for further research and understanding of the effects of stress hormones on higher brain function.
The rest of the text, and a lot of other interesting articles, are accessible here, in the summer issue of Medicinar which topic is mental health.
Translated by: Luka Nalo