Over the past few weeks' blogs, I've talked about how stress can affect the function of our bodies, and this week we'll continue along that same line as we explore further how the brain is impacted by stress. Remembering that cortisol is the end product of our body encountering stressors, let's look at how cortisol affects the brain and nervous system.
Brain Chemistry 101:
The nerves that make up your nervous system communicate through biochemicals called neurotransmitters. To date, we've identified over 100 of these, and they have a wide range of impacts on our function. Cortisol has an impact on many of these, and therefore directly impacts how our brains function. Since most of us want a healthy and optimally functioning brain, controlling stress in our lives and helping our bodies minimize the reaction to stressors can have a profound impact on our brain and mental-emotional health.
One of the biggest impacts cortisol has on our nervous system is to increase the amount of norepinephrine (NE). NE is not only a potent neurotransmitter that stimulates our nervous system into a fight or flight mode, but it is also a hormone that does the same thing on a system wide basis. It does things like increase heart rate and blood pressure, open the bronchioles so we can get more air in the lungs, increases blood flow and reflex speed of the muscles, and shunts more blood to the brain. While more blood to the brain is a good thing, it does this at the expense of the digestive system, thereby making it more difficult to process your food. Long term exposure also poses problems for the heart and blood vessels due to the increased heart rate and blood pressure.
With increased exposure to stressors, the brain releases more corticotropic releasing factor (CRH). In addition to the hormonal aspects we discussed in previous blogs, it also has a local impact on the brain, impairing sleep, enhancing vigilance, and decreasing melatonin. Sleep and vigilance are problems for many, and melatonin is a powerful anti-oxidant our body produces that also helps with sleep. Overall, excessive CRH production creates problems with a restful night's sleep.
Another neurotransmitter that is increased with cortisol is glutamate, which is excitatory to the brain, and can be neurotoxic at high levels. N-methyl-D-aspartic acid (NMDA), which is also increased with cortisol, enhances the effects of glutamate, making it more toxic. It is important for reconsolidation of memories, or what I call "ruminatin' and cogitatin'". When NMDA is high, we tend to spend more time thinking of past events, which can not only make it difficult to concentrate on the moment, but also can significantly increase our stress level. In addition, NMDA itself is neurotoxic when elevated.
While cortisol increases NE, CRH, glutamate, and NMDA (all not good in the long term), it also decreases certain other neurotransmitters, including Brain Derived Neuronal Factor (BDNF), gamma amino butyric acid (GABA), serotonin, dopamine, neuropeptide Y, and galanin. BDNF is something you really want a good amount in your brain, since it is one of the important factors that helps nerve cells heal. GABA is an inhibitory neurotransmitter that helps us focus. Serotonin has a huge impact on mood and keeping us happy while dopamine is necessary for movement and motor function. Neuropeptide Y and galanin protect our brains from the effects of CRH and minimize anxiety. All of these neurotransmitters that are decreased with excessive cortisol we want in good amounts for healthy brains.
Another chemical that is suppressed by cortisol is oxytocin. While most noted as a hormone that stimulates labor and milk production after pregnancy, for many years we were clueless as to why it appeared in males. We now know it plays an important role in our social interactions. Oxytocin is released when we are among those whose company we enjoy, and is very important for decreasing anxiety. It also reduces our blood pressure and increases our pain thresholds. It's has been likened to a "love hormone" as well, since it is what seems to be released during the courtship phase of a relationship and after sex.
Beyond neurotrasmitters, cortisol creates functional changes in the brain. It creates significant problems specifically with memory. Part of the issue deals with transitioning short term memories into long term storage, while it also negatively affects our spatial memory function. This is our ability to remember details about stressful situations, and is one reason why the police may find several witnesses that all saw the exact same thing, yet none of them recall the same scene. By having spatial memory suppressed, it makes the brain "fill in the gaps" with what it thinks should have been happening, or with other memories that may be less traumatic.
As a whole, it can be simply stated that either long term or single high event exposure to stress can significantly increase the risk of affect disorders, most notably mood disorders like anxiety and depression, but also things like schizophrenia, bipolar disorder, paranoia, and delusions. In plain English, your brain does not like stress, and it will become damaged if you don't effectively deal with the stressors in your life.
In future blogs, we'll continue to look at how stress affects us, and how we can minimize it's impact.
Look for future blogs that will give more information and insights into improving your health with natural health care. You can also visit my website, like me on Facebook, follow me on Twitter, or listen to my radio show.
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