Our bodies are ready to protect us from danger as much as possible. The brain is very important in this. The stress response makes sure that our bodies are ready to fight or run away as soon as we sense danger.
In the early stages of evolution, where the stress response comes from, there were often threats to life and limb. In many places, other dangers are now more important. Stress happens, for example, when a person’s sense of self-worth is hurt or when they are afraid of failing or of being separated from important people. Or, sometimes, just when things don’t go the way you want them to. But the stress response is always the same, no matter what causes it. This is true even if you are just thinking about a stressful situation.
Then, different parts of our brain start to work. Like a good team, these areas help us get ready to fight or run away. Some parts of the brain are more “in charge” of processing emotions, while others are more “in charge” of planning and thinking. Still others make sure that the processes that are needed to make the stress hormones come out are started. And before, other parts of the brain analyzed the information from the senses and sent it on.
The brain is the organ that decides which experiences are stressful.
Bruce McEwen, neuroscientist, Rockefeller University, New York
Amygdala, the “fear center” of the brain
The amygdala, a small group of nerve cells in the lower part of the brain that looks like an almond, is a very important part of the brain when it comes to stress and anxiety. It is part of what is known as the Limbic System. This is a group of different brain structures that work together to help the brain process emotions.
Together with other parts of the brain, the amygdala controls how we feel and act when we are in stressful or anxious situations. If it gets signals that something new or dangerous needs more attention, for example, its nerve cells will fire. We are getting smarter and more aware. This happens before we are even aware that we are in danger. At a certain level of nerve activity, the amygdala starts the stress response, which in turn starts the fight-or-flight response.
There are two types of stress reactions.
To trigger the combat and escape reactions, the amygdala uses two methods. The faster way runs through the so-called sympathetic nervous system, which tunes the body to activity. The path over the hypothalamus is a little slower. The hypothalamus is a complex structure in the interbrain that controls the basic functions of our body. For the stress response, he sets in motion a whole cascade of hormones.
The fast way: the sympathetic nervous system
The information “danger” reaches the marrow of the adrenal gland via the nerve strands of the sympathetic nervous system in the spinal cord.There, adrenaline and, to a lesser extent, norepinephrine are released. These hormones are also called catecholamines. For example, they drive up the heartbeat and blood pressure, cause greater tension in the muscles, and cause more blood sugar to be released so that the muscle cells can be better cared for.
The “slow” path over the hypothalamus
At the same time, the amygdala informs the hypothalamus that danger is imminent. The hypothalamus releases hormonal messengers, including the corticotropin-releasing hormone. This hormone acts on the pituitary gland in the brain, also called the pituitary gland. It ensures that it releases another hormone, the adrenocorticotropic hormone, or ACTH for short. It reaches the bark of the adrenal gland with the blood and causes it to release the stress hormone cortisol. Cortisol is a vital glucocorticoid that also has many other functions in the body. If it is present in excess, it can also damage the body.
Together, the hormones and the sympathetic nervous system ensure that our body gets more oxygen and energy to act quickly. Some other hormones, messenger substances, and the body’s own proteins, the so-called cytokines, are also involved in the stress reaction.
What the hormones do
- The breath accelerates.
- The pulse and blood pressure are rising.
- The liver produces more blood sugar.
- The spleen washes out more red blood cells that transport oxygen to the muscles.
- The veins in the muscles widen. This improves blood circulation for the muscles.
- Muscle tone is rising. This often leads to tension. Tremors, foot rockers, and tooth grinding are also related to it.
- The blood clots faster. This protects the body from blood loss.
- The cells produce messenger substances that are important for immune defense.
- Digestion and sexual functions are declining. That saves energy.
Stress and memory
The amygdala does more than just start the stress response. It also helps an important part of the brain that stores memories, the hippocampus, to remember the stressful event well. We learn to be careful around the stressor this way. If we end up in a similar situation again, the stress response happens even more quickly.
Researchers have found that long-term stress can hurt the way cells work in the hippocampus. They are part of the nerve cell and help the body learn new things. If they get smaller, it hurts our ability to remember.
Thinking and stress
The amygdala is also very close to the part of the brain that does “thinking,” especially the forehead lobe, which is a newer part of the brain. It helps you keep your feelings in check. He sits behind his head, as the name suggests. The prefrontal cortex is another name for it. We can change how we feel by analyzing it and thinking logically about it. He is a big part of how we decide whether a stressor is manageable or not and how we act in stressful situations. But long-term stress can change the prefrontal cortex, which makes it harder to make important decisions.
built-in stress brake
We usually get upset again after stress, which is a good thing. This is made easier by a built-in stress brake. If there is enough of the stress hormone cortisol in the blood, the glucocorticoid receptors in the glandular system and brain will notice. Because of this, the adrenal cortex stops making more cortisol. The part of the nervous system that calms the body, called the parasympathetic nervous system, starts to work. We’ll calm down and take it easy.
When the hormones become out of control
If hormones don’t work together as well as they should, things are different. For example, if there aren’t enough receptors, you could notice that there is enough cortisol. or if the ones that are already there don’t work right. Then the hypothalamus, pituitary gland, and adrenal gland become too active. Too much cortisol is produced.
In the worst cases, this can cause mental disorders, loss of brain tissue, and problems with the immune system. Depression and metabolic disorders that make people more likely to get diabetes are also linked to this factor.
Early traumatic experiences affect the stress response.
When a child is under a lot of stress when they are young, it can change how the genes that control the stress response work. This can make stress hormones come out faster and more strongly. Animal tests done by neuroscientists at the Max Planck Institute for Psychiatry in Munich proved this. This effect will always be there. People who have been through a traumatic event, such as a natural disaster, abuse, or violence, may also have similar results if they have certain genetic traits. According to scientists, such people are more likely to experience stress throughout their lives, which could result in depression or anxiety disorders.
