How Stress Affects The Body

We talk about ‘stress’ as a broad term. Most know what it means as a general state, but aren’t necessarily aware of all the biological processes that it triggers – or their implications on our health.

Here’s a quick look at what goes on in our body when it’s under stress, along with how its effects can influence our health over time.


When a threat is detected
Our brains are incredibly effective at recognising danger. At the first instance of a perceived threat, the brain’s hypothalamus signals the pituitary gland to secrete a hormone called ACTH (adrenocorticotrophic hormone).

ACTH enters the bloodstream and activates the adrenal glands (small glands found on top of our kidneys), which signals them to release adrenaline, noradrenaline and cortisol directly into our blood stream.

Together, these hormones prime our body to escape or fight. They do this by –


Suppressing ‘non-essential’ functions
In the context of an immediate threat, certain functions like our digestion, immune function and the formation of new bones aren’t essential.

Physiological functions like these are suppressed, to focus our energy towards the ones that help us run away or beat the threat. Adrenaline and noradrenaline cause the blood vessels in our digestive tract to constrict, reducing the flow of blood to it and, consequently, limiting its function. This is the reason that we feel “butterflies in our stomach” when we are nervous.

Cortisol suppresses our immune system and even blocks the body’s absorption of vitamin D and calcium, to slow down the formation of bone tissue.


Making fuel available, for energy
Adrenaline shuts down the production of ‘insulin’, a hormone secreted by the pancreas that otherwise helps our cells take up the glucose from our blood.

Without insulin, our blood’s circulating levels of glucose are higher, giving our muscle cells ready access to energy, for any quick movements.

Similarly, cortisol helps break down our body’s stored fat into free fatty acids, to make them available for use as fuel as well.


Increasing our heart rate and blood pressure
In doing so, these hormones help the blood’s circulating levels of fuel move faster towards our muscle cells.


Priming our muscles for energy, speed and strength
Both adrenaline and noradrenaline help dilate the blood vessels in major muscle groups (like our legs), to allow blood to flood into the muscles and provide them with fuel. They also increase the tension in the muscles, keeping them in a semi-contracted state for increased speed and strength.


Increasing tunnel vision
To enhance focus on the immediate threat in front of us, these hormones help dilate our pupils and decrease our peripheral vision.


Increase our blood’s clotting ability
Cortisol can help our blood increase its clotting ability, which helps prevents severe blood loss in the event of injury.

While these effects may seem less than helpful in the context of urban lives, they were (and still can be) incredibly helpful when we’re in imminent danger.

The ability to focus on the threat and having muscles that are fueled, semi-contracted and primed to speedily run away were evolutionary benefits that helped us survive, even if other functions such as digestion and immunity were temporarily suppressed.

The problem, however, is that our bodies can have a hard time differentiating between the stress of a predator and the stress that we face today- such as meeting deadlines. Constant exposure to work stress, for example, isn’t a threat to survival but will still trigger the same response in our bodies.

Having chronically elevated levels of these stress hormones then leads to prolonged effects, which isn’t great for our health.

For instance, a decrease in our body’s insulin secretion, can increase the risk of diabetes. The chronic suppression of our immune system can make us susceptible to infections. Reduced blood flow to the digestive tract leads to digestive issues.

These and all the other effects of stress make it important for us to control our body’s response to it. Simple ways to do this include:


Exercise is perceived as a stressor, but our body has the mechanisms to adapt to it. That’s how we get stronger and fitter over time. As this happens, our body also gets better at handling other forms of stress.


Yoga and breathing exercises
Yoga has been shown to decrease our body’s levels of cortisol, which helps limit its effects in our body.

An interesting study has shown that deep, diaphragmatic breathing (breathing “from your stomach”) at a rate of 4 deep breaths per minute can reduce cortisol levels. Controlled breathing can help us regulate our stress response and performing breathing exercises on a regular basis can alleviate chronic stress.


Getting adequate sleep can help reduce our stress levels

Cortisol and sleep are intrinsically linked. Independent of its role in the stress response, cortisol also plays a role in our sleep cycle.

Our body begins to produce small amounts of cortisol 2-3 hours after we fall asleep and continues to do so for the remainder of our sleep, reaching peak cortisol levels 60 minutes after we wake up. The levels then dip through the day, to the point where they’re back to being low, in order for us to fall back to sleep.

Inadequate sleep has been shown to increase our cortisol levels the following evening, making it harder to fall asleep, and disrupting our balance of stress hormones. This can contribute to chronically elevated levels of cortisol.

Sleep deprivation is also a major driver of stress; given that stress makes it more difficult to sleep, this can lead to a vicious cycle.

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