Critically discuss how our knowledge of cortisol and stress response informs our understanding of the relationship between psychological stress and biological dysfunction in brain activity.
This essay will discuss how our knowledge of cortisol and stress response informs our understanding of the relationship between psychological stress and biological dysfunction in brain activity.
In its basic form, in order to protect us from external threats, the brain needs to respond to help us to deal with the external threat. This comes down to basic survival needs. In other words, an environmental stressor results in a biological response in the brain and as this essay will discuss, cortisol plays an important role in that biological response. However, it appears that this response hasn’t evolved to determine the difference between a threat to our survival like having to run away from a saber tooth tiger and therefore many psychological stressors we experience due to our interpretation of specific events, such as everyday stressors like deadlines, or dealing with more difficult situations such as a death in the family. In this case the result can be a feeling of chronic stress which then leads to biological dysfunction in brain activity.
Cortisol is one of the main hormones involved in this process. Cortisol is secreted by the hypothalamus-pituitary-adrenal (HPA) axis when stimulated by the pre-frontal cortex and the amygdala, that is essentially a psychological stress gives rise to a biological response (Lupien et al, 2009).
The biological response to response to acute stress is indeed a useful biological response in the brain (as well as outside the brain) to help us to deal with the stressful situation. The increase in secretion of cortisol enhances neural signalling and therefore brain function by increasing the neurotransmitter glutamate and the number of receptors that can receive the required signals which improve memory and thinking required for an appropriate response. (Popoli et al 2012)
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While the acute response is certainly beneficial, the problem is when the problem becomes chronic. That is when we are in a constant state of psychological stress, biological dysfunction in brain activity will occur. In this case, it has been shown that glial cells are unable to recycle excess neurotransmitters such as glutamate which then build up and are unfortunately toxic in the brain. It has also been shown that increased numbers of neurotransmitter receptors result in dendrite shrinkage and normal neurogenesis in the hippocampal region. Neurons are essentially killed off and volume of the frontal lobe and the hippocampus are essentially reduced (Popoli et al., 2012)
Interestingly, it has also been shown that chronic stress has also leads to increased volume of the amygdala. This would seem to indicate that the person then becomes far better at detecting fears and threats. (Lupien et al., 2009). This would perpetuate the person’s ability to perceive situations as more stressful than they really are and therefore elicit more biological brain dysfunction. It appears to be a perpetuating cycle.
As an example, the neurochemistry of someone who is suffering from depression is essentially the same as the neurochemistry of someone who is experiencing an abnormal stress response. It has also been shown that all individuals have a different genetic predisposition to responding to stress and this can be exacerbated by biological dysfunction caused by chronic stress. (Gulyaeva, 2018)
The impact of stress on pre-cortical function causing increased symptoms with other mental illnesses such as schizophrenia, bi-polar and PTSD has also been noted. (Hains & Arnsten, 2008) (Admon et al., 2009) Both of these papers looked at both the predisposition to stress as well as the biological dysfunction caused by chronic stress. People can also be impacted by stress differently at different times throughout their life. (Lupien et al., 2009)
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So it can be seen that chronic psychological stress will cause biological dysfunction in the brain by increasing the amount of cortisol in the brain, and thereby changing the neurochemistry, when it is secreted in excessive amounts. A person’s predisposition to how they interpret psychological stresses will impact how much cortisol is secreted and prolonged excessive amounts will result in long term changes in the brain, making it more prone to the mental disorder.
As a result, it would seem that it is necessary to work with the individual to improve their cognition of certain events. It would make sense that if people can view certain events as being less stressful, then the biological responses and dysfunctions as a result of stress can also be reduced.
- Admon, R., Lubin, G., Stern, O., Rosenberg, K., Sela, L., Ben-Ami, H., & Hendler, T. (2009). Human vulnerability to stress depends on amygdala’s predisposition and hippocampal plasticity. Proceedings of the National Academy of Sciences, 106(33), 14120–14125. https://doi.org/10.1073/pnas.0903183106
- Gulyaeva, N. V. (2018). The Neurochemistry of Stress: the Chemistry of the Stress Response and Stress Vulnerability. Neurochemical Journal, 12(2), 117–120. https://doi.org/10.1134/S1819712418020058
- Hains, A. B., & Arnsten, A. F. T. (2008). Molecular mechanisms of stress-induced prefrontal cortical impairment: Implications for mental illness. Learning & Memory, 15(8), 551–564. https://doi.org/10.1101/lm.921708
- Lupien, S. J., McEwen, B. S., Gunnar, M. R., & Heim, C. (2009). Effects of stress throughout the lifespan on the brain, behaviour and cognition. Nature Reviews Neuroscience, 10(6), 434–445. https://doi.org/10.1038/nrn2639
- Popoli, M., Yan, Z., McEwen, B. S., & Sanacora, G. (2012). The stressed synapse: the impact of stress and glucocorticoids on glutamate transmission. Nature Reviews Neuroscience, 13(1), 22–37. https://doi.org/10.1038/nrn3138
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