Nervous System

• In order to survive, organisms must; find favourable external conditions, find food, avoid harm
• changes in the environment (stimuli) are detected by receptor cells
• receptor cells are located in the sense organs (i.e. the eyes and nose) and in the body (i.e. pressure receptors in the blood vessels)
• receptor cells send signals via either the nervous system or the hormonal system to the body's co-ordination centres in the brain or spinal cord
• the co-ordination centres then send signals to the responders, known as the effectors
• effectors can be either muscles or glands
• the human nervous system consists of the central nervous system (the CNS) which includes the brain and spinal cord, and the peripheral nervous system (PNS) which includes all the nerves in the body