In biology, the nervous system is a highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. Invertebrates, it consists of two main parts, called the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS contains the brain and spinal cord. The nervous system is involved in receiving information about the environment around us (sensory functions, sensation) and generating responses to that information (motor functions, responses) and coordinating the two (integration) Sensation. The nervous system in a human is made of the brain, spinal cord, sensory organs and all the neurons that serve as communication channels between the various organs of the body. The peripheral nervous system is made up of nerves that branch off from the spinal cord and extend to all parts of the body.