What are the hormones of stress?
For our survival, the body sets up stress mechanisms which are a set of reactions our body resorts to when faced with a threatening or new situation. The stress perceived by our brain then triggers safeguard reactions with the production of hormones. It is this “function” that has enabled us to survive over the millennia by escaping dangers and then gradually adapting to new environments, changes and evolution.
Stressors today are different from those experienced by prehistoric man. Nowadays a reaction of stress is rarely triggered by an encounter with a wild beast (though it may happen too…) but by social and / or professional situations which are more or less felt as stressful agents: a verbal threat, an exam, a competition, financial problems, family problems, an accident, noise, etc. The threats or stimuli have changed but our basic reactions remain the same, we produce exactly the same hormones whatever the stress.
The effects of stress on our brain
Faced with stimuli, our whole organism urges the brain, body and organs to mobilize everything it needs to respond to the threat.
The stimuli first reach the areas of the brain involved in the management of emotions, namely the amygdala, then the hippocampus and the prefrontal cortex.
The amygdala is the part of our brain that is close to the hippocampus. It is the entry route for information received by our five senses and it will guide our reactions. It has many functions.
- It therefore plays an important role in the functions relating to decision-making, pleasure, memory.
- The amygdala allows the detection and processing of emotional information; it enables us to feel our own emotions but also perceive those of others. Whether positive or negative, the amygdala will then identify the emotions concerned and associate them with behavioral and physiological responses. The amygdala functions like the “alarm” system of our body.
Under stress, the amygdala increases significantly in size. This dysfunction has important consequences such as irritability, hypervigilance or agitation linked to a state of anxiety.
The hippocampus is a brain structure that participates in essential functions such as regulating the mood, acquiring knowledge, memory, concentration, and more generally it helps the individual adapt to his environment.
Much neuroscience work shows that exposure to chronic stress affects the hippocampus. Indeed, it seems that the longer the episodes of stress, the more the hippocampus decreases, which can lead to memory problems.
The prefrontal cortex
It is a brain structure located behind the forehead, and the center of decision-making, the key that regulates our composure. Unlike the amygdala and the hippocampus which belong to the limbic system and which dominate our behavior which is related to our emotions, the prefrontal cortex is in charge of our capacity of adaptation. It is the seat of intelligence, of initiative, of decision-making.
Some specific research has shown that in people under chronic stress the volume of gray matter, present in particular in the prefrontal cortex, tends to decrease. A decrease in blood flow and glucose metabolism at the prefrontal level has also been observed in persons subject to chronic stress. This can lead to inability to control emotions, make decisions, or adapt their attitudes to suit various situations.
All of these stimuli will then release several hormones and neurotransmitters.
Neurotransmitters and hormones involved in stress
- A hormone is a chemical molecule produced by a specific gland or tissue, which travels through the bloodstream and acts at a distance to ensure the transmission of messages between organs.
- Neurotransmitters are hormonal chemical signals that relay signals from one area of the brain to another. They therefore transmit the nerve impulse (the potential for action) between neurons. There are inhibitory or excitatory neurotransmitters.
The neurotransmitter GABA is an inhibitor that regulates anxiety by decreasing the activity of the neurons on which it binds. It is the main inhibitory neurotransmitter in the nervous system.
Other neurotransmitters also act on the alarm system:
- serotonin regulates temperature, sleep, mood, appetite and pain
- glutamate is a memory stimulant
- noradrenaline activates attention, emotions, dreams, sleep or even learning
- acetylcholine is involved in wakefulness, attention, anger, aggression, sexuality and thirst. It triggers muscle contraction and stimulates the secretion of hormones
- dopamine, involved in the control of movement and posture, also regulates the mood
Behind the wide range of physical and mental responses to stress are a number of hormones.
- noradrenaline, the precursor to adrenaline, is released by the adrenal glands into the bloodstream after receiving a message from the brain that a stressful situation has arisen. It promotes the contraction of blood vessels and therefore helps to increase blood pressure and heart rate. It allows us to react to a dangerous situation and also focus all our attention on it.
- cortisol, secreted by the adrenal glands, regulates blood pressure, heart and immune function, and provides the brain with sufficient energy to prepare it for stress. This hormone is released shortly after adrenaline.
- adrenocorticotrophin (ACTH) is secreted by the pituitary gland, which is active under the influence of a hormone released by the hypothalamus. ACTH then circulates in the blood and causes the release of cortisol in the adrenal glands.
- oxytocin, the hormone of social bond and attachment, regulator of anxiety, is produced mainly by the hypothalamus (it also plays a neurotransmitter role) and passes into the blood at the level of the pituitary gland to be distributed to organs.
- the antidiuretic hormone vasopressin, increases water permeability and therefore decreases the volume of urine, regulates blood pressure as a vasoconstrictor, plays a role in anxiety.
The adaptation reaction to a stressful situation
The role of these neurotransmitters and hormones is to enable the body to free up the necessary resources in the face of the perceived threat. This biological reaction takes place through several stages.
- 1.The shock stage. During this stage, all our senses are mobilized and send to the brain all that is perceived. During this stage, can be spotted certain physical manifestations such as goosebumps, a knotted stomach, shaking, sweating, or even feeling dizzy.
- 2. The energy mobilization stage. Our sympathetic nervous system is activated. The body takes action to flee or fight. The adrenal glands release adrenaline and cortisol, which results in almost immediate physiological changes:
- Respiratory: increase in frequency to provide more oxygen.
- Muscle: increased oxygenation and therefore energy to run faster or hit harder, muscle tension.
- Cardiac: increased rate, to deliver more oxygen.
- Cutaneous: hairs that stand on end, red cheeks, vasoconstriction to reduce bleeding, sweat is produced to cool the body.
- Blood: reduced clotting time to decrease bleeding, increased blood sugar to increase energy intake. Dilation of the blood vessels to supply more blood to large muscle groups. The liver releases stored glucose to increase the amount of energy.
- Cerebral: hyper-oxygenation to increase our level of vigilance.
- Pupils dilate to improve vision.
- 3. The stage of consumption of energy reserves. If the stress continues, the body begins to use existing energy stores, releasing it as an extra boost with the release of more sugar for the brain and fat for the muscles.
Cortisol is mainly produced during this stage. In addition to the extra discharge of energy, cortisol alleviates the pain and gives the person the ability to continue to fight or flee.
- 4. The stage of draining energy reserves. When your body has been exposed to large doses of stress, it has been able to respond to it by producing many hormones. Not all of them are good for your body and therefore they must be evacuated. This is mainly the case with Cortisol. It’s time to activate the other part of our nervous system, the parasympathetic system, that of rest and recovery.