The Mind-Body Cure. Bal Pawa
recovery. Cortisol and adrenaline surge through our blood vessels, and they affect almost every tissue in the body including the brain (ironically, the same organ that triggered their production). Why? The neural pathway carrying information from the ANS overlaps with the neural pathway carrying specific memories with associated emotions from the limbic system. In other words, the brain cannot discern between real physical or emotional threats and perceived emotional ones. When excessive amounts of the chemicals that mobilize the body for an emergency circulate in the body for too long, they reinforce memories with extra strength so the body never forgets them. In effect, the stress hormones cause many changes in the brain. The neural pathway gets hijacked, and subconscious memories can cause a flood of stress hormones even when we are relaxing.
While the prefrontal cortex of our brain has become highly sophisticated, the brainstem, where many of the ANS pathways begin, has not evolved at the same pace and remains primitive. It does not discern the difference between physical threats and thoughts of anger or jealousy. It processes all these negative emotions as danger signals.
Our brain has a more negative bias than a positive one. While some animals that have escaped a near-fatal attack can literally ruffle their feathers and move on, human brains can re-create a stressful event by thought alone. Stress pathways become hardwired. We look for what is missing. We focus on the worst-case scenarios and worry about outcomes that have not happened yet. We forecast the future rather than live in the present. Worse than that, we have a rewind button that automatically replays old tapes of bad memories. This potent combination leads to ongoing surges of stress hormones. Chronic exposure to stress hormones affects the brain, both directly and indirectly.
➤ Direct Effects of Chronic Stress on the Brain
The nervous system uses a system of nerve cells, or neurons, to take up, process, and transmit information through electrical and chemical signals (Figure 2.4). The brain alone contains about 100 million neurons and 100 trillion connections.2 Each of these cells, which is about a tenth the diameter of a human hair, has three parts. The dendrites are treelike branches that receive input from other neurons. The cell body is attached to the dendrites and contains the DNA of the cell. The axons are wires of various lengths that carry electrical impulses at high speeds toward dendrites of other neurons. These impulses—which carry either excitatory (encourages neurons to fire) or inhibitory (discourages neurons from firing) messages—are transmitted across a gap called a synapse.
A neuron looks like a thin tree. It consists of a nucleus, which is embedded within a larger structure known as the cell body. From the cell body, branches called dendrites sprout. The axon resembles a tree trunk, which then splits into root-like structures. At the tips of these roots are the synaptic terminals. The space where the synaptic terminal communicates with another neuron's dendrite is called the synapse.
Science reveals that neurons that “fire together” in a repeated pattern establish permanent neural pathways: they “wire together.” The communication between neurons is carried out by a number of neurotransmitters. Some cause arousal in the brain, others drowsiness; some focus your attention, others are associated with memory and mood. Over time, exposure to chronic levels of stress hormones changes our neural chemistry and the size and shape of parts of the brain.
Chronic stress changes our neural chemistry by altering neurotransmitters such as serotonin and dopamine. Ordinarily, serotonin is an inhibitory neurotransmitter that stabilizes our mood and balances the number of excitatory neurotransmitters being fired into our brain. Dopamine is usually the “feel-good” chemical that can be both an inhibitory and excitatory neurotransmitter. If our dopamine levels are balanced, our body can reduce any symptoms of anxiety, depression, and stress. But when we are anxious and under chronic stress, the brain begins to produce an overabundance of fear-related neurotransmitters, such as adrenaline and norepinephrine, and fewer neurotransmitters associated with happiness and relaxation, such as dopamine and serotonin. To compensate, the brain creates more receptors to handle the extra fear neurotransmitters and fewer serotonin receptors, which it deems less necessary. The result is that we feel anxious more often than we feel relaxed. Some people can live in a perpetual fight-or-flight reaction, while others have such extreme anxiety they develop a panic disorder, which may require medication.
Chronic stress can also directly change the shape and size of certain areas in the brain. In neuroscience, we call this ability of the brain to change in shape and size neuroplasticity, and it can be both positive and negative. Long-term exposure to the stress hormone cortisol appears to cause brain neurons to shrink and interferes with their ability to send and receive information. As a result, the hippocampus becomes smaller—stress actually shrinks our brain! On the one hand, stress affects our ability to retrieve information, pay attention, or stay focused. On the other hand, the amygdala, the center for the fear reaction, becomes enlarged in chronically stressed people. We become more anxious and more fearful, and those neurons then start to wire together. For example, using MRI scans we can see that the shape and size of various brain structures are different in individuals who have post-traumatic stress disorder (PTSD).
➤ Indirect Effects of Chronic Stress on the Brain
Indirectly, stress hormones cause changes in the gut (our second brain) as well as in many other systems in the body. The gut damage from stress is especially relevant to the brain for several reasons. It impacts the production of serotonin, since our gut manufactures between 80 and 85 percent of our body’s serotonin. Gut damage causes local inflammation that eventually finds its way to the brain and other organs. And stress appears to interfere with the way the bacteria in our gut communicate with our brain. Stress hormones also cause lack of sleep, wearing down the normal capacity of the brain to detoxify and repair itself from daily use. Overall, chronic stress exposes the brain to more inflammation.
Another indirect effect of stress on the brain is the poor diet choices made by people under stress. Stressed individuals tend to eat poorly or snack on junk food, drink more alcohol, or even abuse drugs (both prescription and recreational), which exposes the brain to more toxins. Stressed people tend to become sedentary. Lack of regular exercise is also detrimental to the brain, since the increased blood flow during exercise is good for circulation and oxygenation.
Chronic stress also changes electrical brain waves, which we can measure with an electroencephalogram (EEG) machine. When excessive cortisol disrupts the electrical wave patterns, it changes the neurochemicals in the brain, which causes arousal or alertness. Chronic stress can disrupt our sleep-wake cycles and change our normal circadian rhythms. Sleep deprivation is common in people with unresolved stress. Chronic sleep deprivation is a health risk for heart disease and diabetes and negatively affects brain memory and concentration, leading scientists to correlate it with dementia.
Remember, however, that our mind has dominance over the brain and can regulate the ANS to a great degree. To achieve health, we must learn to pump the brakes and turn off the constant flow of gas. We can cultivate a healthy brain by being aware of our beliefs and internal thoughts. By learning to challenge automatic thoughts, we can consciously replace them with intentional ones, which creates new neural thought patterns. New thought patterns lead to different behavioral choices, which first become traits and eventually turn into habits. When these thought patterns include a health mindset and positive beliefs, they are the foundation for long-term physical and emotional health.
HOW TO SHORT-CIRCUIT STRESS HORMONES AND CREATE A HEALTHY BRAIN
To create better neural pathways, we have to voluntarily or consciously put on the brakes to help neutralize the stress response. To do this, we need to remain aware of our automatic thoughts and choices—catching them before they enter our mind and chasing them out if they sneak in. Our ability to choose one thought over another is one of the most powerful tools we have.