Our entire body is “wired”, so to speak. Every organ and muscle is connected to the brain. Our skin has many sensors that are connected to our brain. Our nervous system can be thought of as a communication system, with signals going from our brains to our bodies, and from our bodies to our brains.
For those of us who find maps helpful, this post sets out a very generalized map of our nervous system. The central nervous system (“CNS”) consists of the brain and spinal cord. The brain can be thought of as a central processor, and the spinal cord as a connector between the brain and body.
While the peripheral nervous system (“PNS”) is usually defined as all the nerves outside the central nervous system, it also includes the cranial nerves and the spinal nerves. It has three main divisions: (1) the somatic nervous system (“SoNS”), (2) the autonomic nervous system (“ANS”) which, in turn, is divided into (a) the sympathetic nervous system (“SNS”), and (b) the parasympathetic nervous system (“PSNS”); and (3) the enteric nervous system (“ENS”).
The somatic nervous system deals with all voluntary muscle movements and with processing external sensory information (sight, sound, touch). Its nerves connect to the skin, sensory organs, and all skeletal muscles.
The autonomic nervous system is all about homeostasis (maintaining a steady and normal internal environment), with the sympathetic and parasympathetic nervous systems complementing each other. In the fight-or-flight response, the sympathetic nervous system increases blood flow to support movement. “Rest and digest” describes the parasympathetic functions.
The enteric nervous system is a complex web of nerves inside the walls of the gut, pancreas and gallbladder. While it is connected to both the sympathetic and parasympathetic nervous systems, the enteric nervous system can act independently, as it does to maintain gut wall tension and movement.
To summarize, the nervous system can be categorized as:
- Central Nervous System (“CNS”)
- Brain
- Spinal Cord
- Peripheral Nervous System (“PNS”)
- Somatic Nervous System (“SoNS”)
- Autonomic Nervous System (“ANS”)
- Sympathetic Nervous System (“SNS”)
- Parasympathetic Nervous System (“PSNS”)
- Enteric Nervous System
You might find these links helpful. For the brain: BiologyDictionary.net and thebrain.mcgill.ca . For the CNS and PNS: https://pediaa.com/difference-between-central-and-peripheral-nervous-system/ . For the SoNS and ANS: https://pediaa.com/difference-between-somatic-and-autonomic-nervous-system .
