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Exploring the Sympathetic Nervous System

What is the sympathetic nervous system (SNS)?

The sympathetic nervous system (PSNS) is one of two major divisions of the larger autonomic system in your body.


In our sympathetic nervous system, we are in fight or flight mode. I remember it like this: If I saw somebody in an active sympathetic nervous state, I would feel great sympathy for them! They would probably be visibly stressed, possibly running away from danger or perhaps frozen to the spot in fear. Internally, they might be experiencing an elevated heart rate, nausea, shallow breathing, hyper-ventilating, and racing thoughts. They would probably be unable to think about anything except the perceived threat and how they might escape it.


Why does it exist?

It exists to keep us safe and, ultimately, alive.


What happens to us?

Everyone is different, but here's how sympathetic activation might present:

  • Alarm - The brain registers a threat and activates the release of chemicals.

  • These chemicals trigger the heart to start pumping faster, sending blood to the parts of the body you might need to flee or fight (brain, extremities and legs)

  • Adrenal glands release adrenaline and cortisol to keep you on high alert; this then triggers the release of glucose from the liver for fast energy

  • Extra oxygen is released into the bloodstream to assist the body in responding to injury

  • Sight and sound can quickly become sharper; the pupils enlarge to access more light

  • Mouth becomes dry as saliva production is inhibited

  • Physical energy levels are enhanced

  • Perspiration or shivering may occur

  • Bladder relaxes

  • Reproductive system decreases blood flow

  • Airways in your lungs relax to improve oxygen delivery to your lungs

  • Non-essential processes like digestion and rational thought are effectively shut down, but in some cases, the digestive system may seek to purge, which can be inconvenient and highly embarrassing.

Once the perceived danger is dealt with, the body enters the resistance phase:

  • Blood pressure, heart rate and breathing start to regulate

  • The system remains on high alert in case the danger returns

  • With time, the body brings back the digestive system and more rational thinking

  • Exhaustion doesn't always follow, but usually does.

This state of high alert is only designed to be activated by threats, and even then, only until you have escaped the scenario. Sadly for us, evolution has done nothing to teach our brains about the difference between a hungry predator and an unpleasant email exchange. This means two things:

  1. We can become unduly stressed or anxious over minor situations, causing the sympathetic nervous system to take over

  2. This can happen way too often and for such lengthy durations. And this can result in the most severe health conditions and burnout. We just weren't designed to be this stressed out!

Your sympathetic nervous system also activates when your body is under strain, like when you're exercising or are unwell.


The activity also affects your immune system and your body's repair processes. These effects can help your body start repairs on an injury quickly if you get hurt.


Where is the sympathetic nervous system located?

Most signals the sympathetic nervous system sends originate in the spinal cord. The signals leave the spinal cord and activate structures called ganglia. Sympathetic ganglia send the necessary alerts far and wide to different body parts. This could include the heart, lungs, arteries, sweat glands and digestive system.


How can we prevent conditions and problems that affect the sympathetic nervous system?

Prevention can make a big difference with conditions that affect your sympathetic nervous system. Sometimes, we can delay conditions that aren't otherwise preventable. Unfortunately, some conditions, such as those you inherit or have when you're born, aren't avoidable.


The best preventive measures include:

  • Eating a balanced diet. Vitamin deficiencies, especially vitamin B12, can damage the nervous system. You should also avoid overusing vitamins (especially B6, which has toxic effects on the nervous system at high levels).

  • Avoiding abusing drugs and alcohol. Prescription and recreational drug abuse and frequent heavy drinking can have toxic effects and damage the sympathetic nervous system.

  • Staying physically active and maintaining a healthy weight. Type 2 diabetes damages the autonomic nerves over time. That's why preventing it, or at least delaying when it starts, can make a big difference in overall well-being.

  • Wearing safety equipment as needed. Safety equipment can be a big help if you want to prevent nerve damage from injuries, regardless of whether you use the equipment during work or play activities.

  • Managing chronic conditions as recommended. If you have a chronic illness that can damage your nervous system, your healthcare provider can help guide you on how to do that. That guidance can make a big difference in helping you limit the condition's progress or how it affects your life.

What happens if we stay in a state of sympathetic activation for too long?

Symptoms of an overactive or dominant sympathetic nervous system include:

  • Anxiety

  • Panic attacks

  • Nervousness

  • Insomnia

  • Breathlessness

  • Heart palpitations

  • Inability to relax / cannot sit still

  • Jumpy or jittery

  • Poor digestion, fear

  • High blood pressure

  • High cholesterol

Eventually, the over-stimulated nervous system becomes depleted in later stages, which signals the rest of the body to slow down to maintain a 'backup' energy supply if needed for an emergency. This stage is where constant fatigue, lethargy and lack of vitality occur. Usually, many seek some form of artificial stimulation, such as caffeine, salt, energy drinks, sugar (carbohydrates), alcohol (the sugar in alcoholic drinks), drugs and entertainment, which all stimulate a depleted nervous system.


The problem is that these temporary artificial energy boosts are sought more and more often in an attempt to maintain a barely-functioning level of existence. This artificial stimulation 'confuses' the nervous system as it tries to slow the depleted body down to store energy, but the artificial stimulation is actually doing the opposite. This then creates a cascade of events which eventually causes more long-term problems such as underactive thyroid and autoimmune conditions, not to mention adrenal fatigue, which is concurrently created due to the stress and thyroid imbalance.


What can we do when we are in sympathetic activation?

There are many ways to bring the body and mind back to balance; look at my post about Activating the Parasympathetic Nervous System to see some simple, fast ways to calm down.

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