7 Differences Between Sympathetic and Parasympathetic Nervous Systems
The autonomic nervous system (ANS) plays a vital role in regulating many functions that you don’t have to think about, like heart rate, digestion, and gland activity. It’s divided into two key branches: the sympathetic nervous system and the parasympathetic nervous system. While they both serve essential roles in maintaining homeostasis, their functions and effects on the body are vastly different. Here are the seven primary differences between these systems:
Written by
- Redaction Team
- Body, Personal Development
Table of Contents
Primary Function
Sympathetic Nervous System
The sympathetic system is responsible for the “fight or flight” response. It activates the body to respond to stress or danger by:
- Increasing heart rate
- Releasing adrenaline (epinephrine) and norepinephrine
- Redirecting blood flow from non-essential organs to muscles
- Dilating pupils to improve vision
This system prepares the body for action and increases alertness.
Parasympathetic Nervous System
The parasympathetic system promotes a state of rest and recovery, also known as “rest and digest” or “feed and breed.” Its primary functions include:
- Slowing down heart rate
- Stimulating digestion
- Supporting urination and defecation
- Returning the body to a calm and composed state after stress
Neurotransmitters Released
Sympathetic Nervous System
This system primarily uses norepinephrine as its neurotransmitter to activate organs. Additionally, the adrenal glands release epinephrine and norepinephrine into the bloodstream, amplifying the body’s alertness and response.
Parasympathetic Nervous System
The parasympathetic neurons use acetylcholine as their main neurotransmitter. Acetylcholine helps promote relaxation and stimulates functions such as salivation, digestion, and lowering the heart rate.
Nerve Origins in the Body
Sympathetic Nervous System
Sympathetic nerves originate in the thoracic and lumbar regions of the spinal cord. The nerve fibers pass through the sympathetic ganglia, located near the spinal column, to rapidly relay signals to target organs.
Parasympathetic Nervous System
Parasympathetic nerves arise from the cranial nerves (specifically the vagus nerve) and the sacral region of the spinal cord. These nerves travel longer distances to reach their target organs.
Effects on Heart Rate and Blood Pressure
Sympathetic Nervous System
- Increases heart rate to pump more blood to muscles
- Raises blood pressure by constricting blood vessels
Parasympathetic Nervous System
- Decreases heart rate to conserve energy
- Reduces blood pressure, allowing the body to relax
Role in Digestion
Sympathetic Nervous System
The sympathetic system suppresses digestion during stressful situations by:
- Inhibiting saliva production
- Slowing down the movement of the digestive tract
Parasympathetic Nervous System
The parasympathetic system enhances digestion by:
- Stimulating saliva secretion
- Activating smooth muscles in the digestive tract to promote peristalsis
Control of Urination
Sympathetic Nervous System
This system inhibits urination by relaxing the bladder and contracting the sphincter muscles, prioritizing other bodily functions during stress.
Parasympathetic Nervous System
The parasympathetic nervous system restores bladder function by contracting the bladder and relaxing the sphincters, enabling normal urination.
State of the Body
Sympathetic Nervous System
When active, the sympathetic system puts the body’s systems on alert. It redirects resources toward survival functions, preparing the body for immediate action.
Parasympathetic Nervous System
The parasympathetic nervous system helps return the body to a state of calm and recovery, maintaining long-term health by enabling functions like digestion and immune system repair.
Summary Table: Sympathetic vs. Parasympathetic
| Feature | Sympathetic Nervous System | Parasympathetic Nervous System |
|---|---|---|
| Primary Function | Fight or flight | Rest and digest |
| Neurotransmitters | Norepinephrine, epinephrine | Acetylcholine |
| Nerve Origin | Thoracic and lumbar spinal cord | Cranial nerves, sacral spinal cord |
| Heart Rate | Increases | Decreases |
| Digestion | Suppresses | Stimulates |
| Urination | Inhibits | Promotes |
| State of Body | Alert and ready for action | Calm and restorative |
Importance of the Autonomic Nervous System
The autonomic nervous system is critical for survival and well-being. Damage to the nervous system may result in disorders like multiple system atrophy, impacting functions such as heart rate, digestion, and urination. By understanding the differences between the sympathetic and parasympathetic nervous system, it becomes easier to see how the body maintains balance and responds to both stress and relaxation.
More about Body
