The nervous system is the body's control center, comprised of two major parts: the central nervous system (CNS) and the peripheral nervous system (PNS).
Central Nervous System (CNS)
The CNS is the command center, consisting of:
- Brain: The brain controls thought, memory, emotion, and voluntary movement. It's divided into several regions with specialized functions. See this resource for more information on brain structure and function.
- Spinal Cord: The spinal cord acts as a pathway for information between the brain and the rest of the body. It also controls reflexes.
Peripheral Nervous System (PNS)
The PNS extends throughout the body, connecting the CNS to organs, limbs, and skin. It's further divided into:
- Somatic Nervous System: Controls voluntary movements of skeletal muscles.
- Autonomic Nervous System: Controls involuntary functions like heartbeat, digestion, and breathing. This is further subdivided into the sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) nervous systems.
Examples of Nervous System Function
- Reflexes: A quick, involuntary response to a stimulus (e.g., pulling your hand away from a hot stove). This involves the spinal cord primarily, with minimal brain involvement.
- Sensory Perception: The PNS transmits sensory information (sight, sound, touch, taste, smell) to the CNS for processing.
- Motor Control: The CNS sends signals to muscles via the PNS, enabling movement.
The structure of the nervous system is incredibly complex, varying from simple organisms to highly developed brains like those found in humans. Even within a single species, the precise arrangement of neurons can be remarkably consistent, as seen in the nematode Caenorhabditis elegans https://royalsocietypublishing.org/doi/10.1098/rstb.1986.0056. The intricate network of neurons and their connections allows for the sophisticated coordination and control of all bodily functions. Myelin, a fatty substance surrounding many axons, significantly contributes to the efficient transmission of nerve impulses. See this resource on myelin's structure and function.
