Nervous system: One of the regulatory systems made of millions of neurons in precise pathways to transmit electro-chemical impulses, and of neuroglial cells that have several functions, including formation of myelin sheaths of neurons. It consists of the brain and spinal cord (central nervous system [CNS]) and the cranial nerves and spinal nerves (peripheral nervous system), which include the nerves of the autonomic nervous system and its ganglia. Receptors detect external and internal changes and transmit impulses along sensory nerves to the CNS. Receptors are found in the skin, muscles and joints, viscera, and the organs of special sense: the eye, the ear, and organs of taste and smell. The CNS uses this sensory information to initiate appropriate responses to changes. A function specific to the brain is the integration, analysis, and storage of information for possible later use; this function is learning and memory.