When we are stressed, it is our endocrine and nervous systems which kick in and play a major role in how our body reacts to the stressor or stressors. Also known as the ‘fight or flight response’, it is this nervous system pathway which is responsible for secreting hormones as a response to the stressors we face.
Behind the diverse range of both physical and mental reactions that people have to stress are a number of hormones which include adrenaline, norepinephrine, cortisol, oestrogen, testosterone and the neurotransmitters dopamine and serotonin. However, adrenaline, norepinephrine and cortisol are the three major hormones which fuel our ‘fight or flight’ responses.
What is adrenaline and what does it do?
Known commonly as the fight or flight hormone, it is produced by the adrenal glands. It is secreted from the adrenal glands when it receives a message from the brain that a stressful situation may occur or has occurred.
Adrenaline, along with norepinephrine (more on that hormone later), is mainly responsible for the immediate reactions, both physically and physiologically, we have and feel when stressed. Can you remember the last stressful situation you found yourself in, such as being late for work or losing your house keys? You probably dealt with the situation and remained focused, but at the same time your muscles would have been tense, your heart rate would have become elevated, you may have been breathing faster and have even started to sweat. These reactions are all caused by adrenaline. Hundreds of years ago, these same responses would have helped us either run away from or stay and defend ourselves in a dangerous situation.
What is norepinephrine and what does it do?
It is a hormone similar to adrenaline, which is also released from the brain and the adrenal glands.
As with adrenaline, the main role of norepinephrine is to make you alert. When you are stressed, you become more aware and more responsive. Norepinephrine is responsible for shifting blood flow away from areas where it might not be so crucial. So vasoconstriction occurs in areas such as the digestive system and the skin while more essential areas, like the muscles, experience vasodilation, therefore allowing the body to flee or deal with the stressful scene. It is thought that norepinephrine acts as a backup for adrenaline.
What is cortisol and what does it do?
It is a steroid hormone and commonly known as the stress hormone. It is also produced by the adrenal glands.
Cortisol takes longer (minutes rather than seconds) than adrenaline and norepinephrine to be released and for us to feel the effect. This is because the release of cortisol is more complex and involves two additional hormones (corticotropin-releasing hormone and adrenocorticotropic hormone) before adrenaline is released.
In short bursts and with the optimal amount of cortisol release, the hormonal effects are hugely beneficial. For example, cortisol helps to maintain fluid balance and blood pressure as well as regulating other, less necessary body functions at the same time, such as digestion. In these situations, the stress response is self-limiting, and once the stress or threat has passed, hormone levels return to normal.
However, there are situations in which we have low-level, continual stress, such as exams, pressures at work and financial issues, which cause the body to produce and release cortisol. It is this that can cause elevated levels and the situation to become chronic, which can lead to serious health issues. The release of too much cortisol can lead to a suppressed immune system and increase in blood pressure and sugar levels, as well as a decreased libido, and has been linked to contributing to obesity.