The autonomic system is made up of two divisions, the sympathetic and parasympathetic systems. They usually work antagonistically in the organs, but in a well integrated manner. It is the balance of the actions of both divisions that maintains a stable internal environment in the body.
The parasympathetic nervous system is a subdivision of the autonomic nervous system (ANS) which regulates bodily functions which are outside of voluntary control, therefore being automatic. The parasympathetic nervous system is also referred to as the ‘rest and digest’ system as it functions to conserves the body’s natural activity, and relaxes the individual once an emergency has passed.
The sympathetic nervous system (SNS) is involved in regulating autonomic processes. The sympathetic nervous system is involved in preparing the body for stress-related activities, and it slows bodily processes that are less important in emergencies such as digestion. These are processes which are not under direct conscious control, occurring automatically without conscious thought. The SNS also works alongside the parasympathetic nervous system to maintain homeostasis – this is the balance of internal physiological mechanisms essential for all living organisms.
| BASIS OF COMPARISON | SYMPATHETIC NERVOUS SYSTEM | PARASYMPATHETIC NERVOUS SYSTEM |
|---|---|---|
| Meaning | Part of autonomic nervous system that regulates the fight-or-flight response of the body. | Part of autonomic nervous system that controls the general homeostasis i.e. rest-and-digest response of the body. |
| Location | Originates in thoracic and lumbar region. | Originates from cranial region of brain stem and sacral region of spinal cord. |
| Function | Mobilises the body for intense physiological action i.e. makes the body alert, tensed up and speeded towards danger. | Restores the body to go in the relax mode by restricting the high energy activities. |
| Response | Quick | Slow |
| Position of Ganglion | Close to the central nervous system (CNS). | Away from CNS, close to effector. |
| Pre-ganglion fibres | Short | long |
| Post-ganglion fibres | long | Short |
| Coverage and effect of body | Covers the larger area of the body with diffused effect at the target zone. | Covers the smaller area of the body with localised impact on the target area. |
| Outflow | Generates a thoracolumbar outflow. | Generates a craniosacral outflow. |
| Nerves | Adrenergic | Cholinergic |
| Neurotransmitters | Secretes Adrenaline or noradrenaline | Secretes acetylcholine. |
| Cardiovascular system | Enhances the blood pumping in the heart, thus increasing the heart rate. | Relaxes the cardiac muscles, decreasing the heart rate. |
| Respiratory system | Dilates the respiratory airway, increases the breathing rate. | Constricts the respiratory tract, decreases the respiration rate |
| Pupillary action | Pupils dilate | Pupils constrict |
| Sensory awareness | Raises the sensory response | Keep the sensory responses in the normal state |
| Glycogen breakdown | Stimulates the glycogen breakdown mechanism | Does not affect glycogen breakdown |
| Digestive system | Decreases the stomach movements and slow down the digestion process | Increases the stomach movement and fasten the digestion machinery |
| Urinary system | Decreases the urinary output | Increases the urinary output |
| Importance | Produces swift, spontaneous and sudden response in danger or excited state. | Maintains the normal homeostasis of the organism’s body |