In your daily life, you’ve probably been suddenly startled by a loud bang or an unexpected movement. Your heart rate increases, your breathing quickens, and you feel a surge of energy rush through your body. This is your fight-or-flight response in action, an ancient response that makes you ready to react to impending danger in a split second. But what actually causes this intense and immediate reaction? What makes your body prepare for action in the blink of an eye? To understand this, we need to delve deeper into the science behind this response and the crucial role that a specific hormone plays in it.
Which hormone plays the biggest role?
The answer lies in a hormone called cortisol. Cortisol is a hormone produced in the adrenal cortex, a part of the adrenal glands. When we experience stress, a part of our brain called the hypothalamus sends a signal to another gland in the brain called the pituitary gland. This pituitary gland then releases another hormone called adrenocorticotropic hormone (ACTH), which tells the adrenal glands to make and release cortisol into our blood.
Cortisol has several important functions:
- Regulating metabolism : Cortisol helps maintain our blood sugar levels by stimulating the production of glucose in the liver.
- Suppressing the immune system : Cortisol reduces inflammation and can suppress immune system activity.
- Influence blood pressure : Cortisol helps maintain healthy blood pressure.
- Stress Response : Cortisol plays a key role in our response to stress by preparing our body for action.
The fight or flight response
The fight or flight response is an automatic survival mechanism found in all mammals. This response was first described in detail by Walter Cannon in the early 20th century. When we perceive a threat, our body goes into action through a series of physiological changes to prepare us to fight or flee.
When our brain detects a threat, especially through the amygdala which is responsible for emotional processing, it sends an alarm signal to the hypothalamus. This then activates the HPA axis by releasing corticotropin-releasing hormone (CRH), which stimulates the pituitary gland to release ACTH. ACTH stimulates the adrenal glands to produce cortisol and adrenaline. Adrenaline provides quick responses such as increased heart rate and blood pressure, while cortisol provides long-lasting energy.
These released hormones cause several changes in the body. Heart rate and blood pressure increase so that blood is pumped faster to our muscles and vital organs. Our breathing speeds up to bring more oxygen to our muscles. In addition, glucose and fatty acids are released for immediate energy. During these processes, non-essential functions, such as digestion and growth, are suppressed to save energy for the response to the danger.
Evolutionary origin and necessity
The fight or flight response evolved as a crucial mechanism for survival. In prehistoric times, this response was essential to respond to life-threatening situations such as predator attacks. The ability to quickly decide to fight or flee greatly increased our chances of survival.
In early humans, hunter-gatherers living in dangerous environments, the fight-or-flight response was vital to life. Imagine an early human hearing a lion roar in the undergrowth. The immediate response, controlled by the amygdala, prepares the body for a quick escape or defense. The heart rate increases, muscles tense, and glucose is released to provide energy. Without this response, our ancestors would not have been able to react quickly enough to survive.
Why does the reaction persist today?
Although our modern society is very different from that of our ancestors, the fight or flight response is still active in our bodies. Today, we are faced with various stressors such as work pressure, financial worries, social relationships and health problems. Although these stressors are rarely life-threatening, our bodies still respond in the same way.
Interestingly, research on modern-day indigenous populations, who live lifestyles more similar to those of our early ancestors, has shown that these people still exhibit the same fight-or-flight responses in response to threats in their environment. This highlights how deeply ingrained and universal this response is in human biology.
Impact on modern stress and sleep
Modern stressors:
In today’s society, the fight or flight response can be problematic when activated too often or for too long. Chronic stress can lead to constantly elevated cortisol levels, which has negative effects on our health, such as:
- A weakened immune system
- An increased risk of cardiovascular disease
- Weight gain and metabolic problems
- Anxiety and depression
Cortisol and sleep:
Cortisol follows a circadian rhythm, meaning that its levels in our bodies vary throughout the day. Levels peak in the early morning to help us wake up and decline in the evening to help us sleep. Chronic stress can disrupt this rhythm. Elevated cortisol levels during the day can lead to insomnia and poor sleep quality. People who experience persistent stress may find that they have trouble falling asleep or staying asleep, leading to a vicious cycle of fatigue and increased stress.
Conclusion
Cortisol and the fight or flight response play a vital role in how we deal with stress and have deep roots in our evolutionary history. While this response was originally designed to help us survive life-threatening situations, it remains active in our bodies today. Understanding the basics of cortisol and the fight or flight response can help us better understand how to deal with modern stressors and their impact on our health and sleep. By learning how these ancient mechanisms work today, we can develop strategies to better manage stress and thus improve our health and sleep.
Pharmacist Dirk
Founder Metis Supplements
