Welcome back to Part 2 of “Stress - The Mind-Body Connection”. In Part 1, we discovered the science and psychology behind the mind-body disconnect, how hormones affect our perception of the world, how stress produces visible changes in the brain as well as enhanced emotionality, and much more. If you have not read part one, check it out here.
In this article, we’ll explore how stress can actually rewire the brain’s neural architecture, allostasis and the whole-body response to stress, as well as 5 molecules that are required to help rebuild the brain. Let's dive into Part 2 now.
Stress Remodels the Neural Architecture of the Brain
Alterations in the brain are known as “cognitive deficits”. Cognitive deficits can make a person more susceptible to neurological dysfunction. People can become acutely sensitive to stimuli, such as fearful facial expressions due to the amygdalar hyper-responsivity.
As well as the bidirectional relationship of the environment and the mind, the spheres of the brain also correspond with each other. Chronic or severe stress can result in behavioral abnormalities, which can manifest as cognitive impairments.
In one study, animal models were exposed to stress to examine their stress response. They were exposed to physical stress, such as immobilization and restraint stress. Other forms of stress that they were exposed to include predator odor, maternal separation, social defeat and being on a bright, exposed elevated platform. McEwen and colleagues found that 21 days of stress, 6 hours per day, was enough to produce substantial dendritic remodeling in the hippocampal CA3 pyramidal neurons.
The body continually adapts to its environment. The brain is the center for regulating cytoskeleton, epigenetic and nongenomic mechanisms. Stress can remodel the neural architecture of the brain. We now know that gene expression is continually mediated by epigenetic mechanisms to adapt to the environment. Brain-derived neurotrophic factor (BDNF) and endocannabinoids, along with excitatory amino acids and glucocorticoids mediate the response and corresponding changes in the body.
Allostasis and The Whole-Body Response
Allostasis is a process by which the body achieves stability or homeostasis - this process is adaptive and is connected to the whole body. The HPA axis, the autonomic nervous system, the metabolic system, and the pro and anti-inflammatory modulators of the immune system are all involved in the stress response, showing a clear full-body response in the presence of a stressor. If there’s too much stress, then the body can fail to regulate these mechanisms, which, in turn, burns the body out. This is known as “Allostatic Overload”.
Homeostasis is maintained in the body through adapting to stressors via mediators. These mediators include cortisol, adrenalin, the autonomic nervous system, the metabolic system, and the immune system. Allostasis and “Allostatic Overload” are precise biological concepts that describe how the body adapts to stressors.
When someone is stressed, or suffering from a high allostatic load, they might smoke, drink alcohol, eat poorly or sleep less. This, in turn, can result in further physical manifestations of disease.
The Three Main Types of Stress/ Allostatic Load
Three main types of stress the body can undergo are:
1. Good Stress
Good stress is an essential part of life. Good stress is characterized by a brief increase in heart rate and mild hormone rate elevation, the type of stress that helps you get motivated.
2. Tolerable Stress
Tolerable stress is serious, temporary stress. This kind of stress is made tolerable by supportive relationships.
3. Toxic Stress
Toxic stress is the prolonged activation of the stress response, in the absence of supportive relationships. Research at Harvard University shows that toxic stress can alter the developmental processes in children, producing damaging effects on learning, behavior, and health throughout their life.
Adverse Childhood Experiences (ACEs)
Adverse childhood experiences (ACEs) can severely alter the neural architecture of the brain and make a person more susceptible to stress in the future. meaning that tolerable stress can quickly turn into toxic stress. Just one traumatic event (or ACE) can produce long-lasting abnormalities. The same goes for adult trauma, however, in general adults are not as sensitive to adverse experiences. Critical transitional periods of childhood development are notoriously sensitive to stressful experiences and can alter the course of a person’s life.
The way that a person perceives a situation can alter due to ACEs. For example, if a child is neglected or abused, and as such, the bond with their caregiver is weakened. They can experience a lack of social interaction, feel excluded and have an inability to cooperate in social experiences as adults.
Stress Alters The Brain’s Structure and Function
Although the whole body gets involved when there’s a stressful experience, the brain is the main target. Glucocorticoids are excitatory amino acid neurotransmitters that alter the synapse density. Stress, therefore, alters the brain's structure and function.
Molecules Necessary for Brain Remodeling
We now know that the brain can rebuild itself, offering a positive therapeutic advancement for people with neurological impairment. To do so, the correct internal, external and environmental conditions must be present. The adult brain can create new stem cells that can proliferate under the correct circumstances.
There are 5 main groups of molecules that are required for remodeling the brain, as outlined below:
- Brain-Derived Neurotrophic Factor (BDNF) - Facilitates plasticity and growth. Too much BDNF can enhance chronic stress.
- Serine Protease Tissue-Plasminogen Activator (tPA) - Release is regulated by the amygdala, tPA is responsible for stress-induced spine loss in the hippocampus and MeA. Activates secretion of CRF. Required for mitigating stress-induced spine loss.
- Corticotropin-Releasing Factor - secreted by the hippocampus, downregulates spine's RhoA signaling.
- Lipocalin-2 - Protein that downregulates mushroom spines, increases neuronal excitability and anxiety.
- Endocannabinoids - Induced via glucocorticoids, regulates emotions and HPA. Regulated by fatty acid aminohydrolase (FAAH).
Stress-Induced Spine Loss
The serine protease tissue-plasminogen activator (tPA) plays a key role in spine plasticity. In one study researchers compared the impact of chronic restraint stress on the spine density and medial amygdala (MeA) remodeling. Chronic stress was found to cause a significant reduction in spine density. This process exposes a clear connection between the mind and the body via the spine.
The Gut-Brain Connection
The gut-brain connection again shows a clear bidirectional link between the body and the mind. Whereby anxious feelings can be linked to both the stomach and the mind. The gut is sensitive to emotion and as such can get upset due to feelings of anger, anxiety, sadness or euphoria.
Thinking about food will trigger the release of stomach acid in preparation for the food arriving, which makes sense why cooking videos make us hungry. On the flip side, a troubled gastrointestinal tract can produce a troubled mind.
Psychology and physiology combine to produce illness or wellness. Harvard University reviewed 13 studies whereby psychological treatments were given to patients with digestive symptoms and found that these patients recovered better than patients who only received conventional treatments for the gut.
Contrary to previous thinking, the mind and body have a strong non-linear bidirectional relationship. The seemingly disconnected emotional feelings and thoughts can be monitored in the gut, hormones, and the brain. The whole body takes part in the stress response, making it an important factor in life to manage in all situations.
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