Difference Between CNS and PNS
The nervous system in humans is divided into two main parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). Both work together to control and coordinate body functions, but they have different roles and structures.
1. Definition
- CNS (Central Nervous System): The part of the nervous system consisting of the brain and spinal cord. It processes information and controls body activities.
- PNS (Peripheral Nervous System): The network of nerves outside the CNS that connects the CNS to organs, limbs, and skin. It transmits messages to and from the CNS.
2. Components
- CNS: Brain and spinal cord.
- PNS: Cranial nerves (from the brain) and spinal nerves (from the spinal cord).
3. Function
- CNS: Processes, integrates, and stores information, and makes decisions for responses.
- PNS: Carries sensory information to the CNS and transmits motor commands from the CNS to muscles and glands.
4. Control
- CNS: Acts as the control center of the body.
- PNS: Acts as the communication lines linking the CNS with the rest of the body.
5. Protection
- CNS: Protected by skull, vertebral column, meninges, and cerebrospinal fluid.
- PNS: Less protected; nerves are often surrounded by connective tissue sheaths but are more exposed.
6. Speed of Response
- CNS: Processes information rapidly and initiates complex responses.
- PNS: Conducts signals to and from the CNS, enabling reflexes and voluntary actions.
Summary Table:
| Feature | CNS (Central Nervous System) | PNS (Peripheral Nervous System) |
|---|---|---|
| Definition | Brain and spinal cord | Nerves outside CNS |
| Components | Brain, spinal cord | Cranial nerves, spinal nerves |
| Function | Processes and integrates information | Transmits signals to and from CNS |
| Control | Control center | Communication lines |
| Protection | Skull, vertebral column, meninges | Connective tissue sheaths only |
| Speed of Response | Rapid processing | Conduction of impulses to/from CNS |
Key Point:
- CNS: The “brain and spinal cord” control center.
- PNS: The “network of nerves” connecting the CNS to the body.