What is the Sympathetic Nervous System?

Your nervous system is incredibly complex, with several different divisions all working together to help maintain homeostasis throughout the body. One of those divisions is the sympathetic nervous system. In today’s article, we will go over what the sympathetic nervous system is, how it works, the difference between the sympathetic nervous system and the parasympathetic nervous system, and examples of what the sympathetic nervous system does. 

What Is The Sympathetic Nervous System?

The sympathetic nervous system is a division of the nervous system that works to produce localized adjustments throughout the body. This system is activated under conditions of stress, producing an immediate widespread response known as the fight-or-flight response. 

The purpose of this response is to release large quantities of epinephrine from the adrenal gland, an increase in heart rate, and an increase in cardiac output. 

The sympathetic nervous system acts in concert with the other neural or hormonal responses to stress. Chronic stress can lead to a long-term stimulation of fight-or-flight response, which can lead to long-term health issues. Some of these health issues include hyperglycemia, type 2 diabetes, and hypertension. 

What Is The Role Of The Sympathetic Nervous System?

The sympathetic nervous system (SNS), works alongside the parasympathetic nervous system to maintain homeostasis. This is crucial as the balance of internal physiological mechanisms is essential in all living organisms. The SNS works to require quick responses including:

  • Increased heart rate
  • Dilation of the pupils
  • Dilated muscles
  • Secretion of sweat glands
  • Relaxation of the bladder
  • Increased alertness

Actions such as sweating to cool down the body or regulating the heart rate help the SNS maintain homeostasis. The SNS stimulates organs, which differs from the parasympathetic nervous system, which slows down physiological processes. 

What Are The Main Functions Of The Sympathetic Nervous System?

The SNS will send a flash flood of hormones to boost the body’s alertness and heart rate. During this response, breathing will quicken, fresh oxygen will be delivered to the brain, and glucose is shot into the bloodstream for a quick energy boost. This response happens so quickly that most people don’t realize what’s taking place. For example, you may swerve out of the way of an oncoming car before fully registering that the car is coming toward you. 

The SNS is not responsible for de-stressing the body once you’re out of a high-stress situation. This responsibility falls on the parasympathetic nervous system. This system encourages the body to rest and digest. Blood pressure, breathing rate, and hormone flow will return to normal levels as the body settles into homeostasis. 

Why Is It Called The Sympathetic Nervous System?

The sympathetic nervous system gets its name from “sympathy” as it is a connection between parts. It was first used medically by Galen in the 18th century. Jacob B. Winslow applied the term specifically to nerves in the 18th century. 

What Is An Example Of A Sympathetic Nervous System?

The fight-or-flight response is a perfect example of the sympathetic nervous system. This response was first described by Walter Bradford Cannon, who stated that animals react to threats with a general discharge of the sympathetic nervous system. This process primed the animal for fighting or fleeing. Some of the physical reactions associated with the SNS include:

  • Acceleration of heart and lung action
  • Dilation of blood vessels for muscles
  • Relaxation of bladder
  • Paling or flushing
  • Constriction of blood vessels in many parts of the body
  • Dilation of the pupil
  • Tunnel vision

Researchers believe that, in prehistoric times, the human fight-or-flight response manifested in aggressiveness. In current times, the fight-or-flight response has assumed a wider range of behaviors. 

What Is The Difference Between Parasympathetic And Sympathetic?

The parasympathetic and sympathetic systems work in unison to help maintain homeostasis throughout the body. The sympathetic nervous system, as mentioned earlier, prepares the body for fight and flight response. Meanwhile, the parasympathetic nervous system restores the body to a calm and composed state. 

The SNS releases the hormones epinephrine and norepinephrine that accelerate the heart rate. Meanwhile, the parasympathetic nervous system releases acetylcholine, which slows down the heart rate. The parasympathetic nervous system is known to begin what is called the rest-and-digest response.