Difference Between Sympathetic and Parasympathetic Nervous Systems
The autonomic nervous system (ANS) controls involuntary body functions like heartbeat, digestion, and breathing. It is divided into sympathetic and parasympathetic divisions, which often have opposite effects on the organs.
1. Definition
- Sympathetic Nervous System (SNS): Prepares the body for “fight or flight” situations by increasing alertness and energy use.
- Parasympathetic Nervous System (PNS): Prepares the body for “rest and digest” activities by conserving energy and promoting recovery.
2. Function
- SNS: Speeds up heart rate, dilates pupils, inhibits digestion, stimulates release of adrenaline.
- PNS: Slows down heart rate, constricts pupils, stimulates digestion, promotes relaxation.
3. Origin
- SNS: Thoracic and lumbar regions of the spinal cord.
- PNS: Brainstem and sacral region of the spinal cord.
4. Effect on Organs
- SNS: Prepares body for emergencies or stress.
- PNS: Maintains normal body functions at rest.
5. Neurotransmitters
- SNS: Uses norepinephrine and adrenaline.
- PNS: Uses acetylcholine.
Summary Table:
| Feature | Sympathetic Nervous System (SNS) | Parasympathetic Nervous System (PNS) |
|---|---|---|
| Function | “Fight or flight” response | “Rest and digest” response |
| Heart Rate | Increases | Decreases |
| Digestion | Inhibits | Stimulates |
| Pupil | Dilates | Constricts |
| Origin | Thoracic and lumbar spinal cord | Brainstem and sacral spinal cord |
| Neurotransmitter | Norepinephrine, adrenaline | Acetylcholine |
| Overall Effect | Prepares body for stress/emergency | Conserves energy and restores body |
Key Point:
- Sympathetic NS: Activates the body for action and stress.
- Parasympathetic NS: Calms the body and supports recovery and digestion.