The nervous system can be anatomically divided into the central nervous system (CNS), which consists of the brain and the spinal cord, and the peripheral nervous system (PNS), which consists of sensory receptors, the nerves outside the CNS and their associated ganglia, and efferent motor endings.
Functionally, the nervous system can be divided into a sensory component, which detects stimuli and transmits electrical impulses to the CNS, and a motor portion, which transmits impulses from the CNS to the muscles and glands of the body, which then respond by secretion or contraction. The motor portion can be further divided into the somatic and autonomic components. The somatic nervous system is also known as the voluntary system because it allows us to consciously control our skeletal muscles. The autonomic nervous system in contrast subconsciously controls the activity of out smooth muscles, cardiac muscles and glands.
The nervous system fulfills three main functions:
- Sensory Input - via receptors, the nervous system monitors changes in the environment both outside and within the body;
- Integration – the CNS processes the sensory inputs, interprets and integrates them;
- Motor Output – the nervous system triggers a response by stimulating the effector organs; muscles and glands.