B1.2 THE NERVOUS SYSTEM (1/2) The human nervous system consists of the central nervous system (brain, spinal chord) and the peripheral nervous system (neurones that carry information to/from CNS). The information flow from a stimulus to a response goes as follows: Stimulus > Receptor > Sensory neurone > Relay neurone > Motor neurone > Effector > ResponseWhere two neurones meet there is a tiny gap called a synapse. Information crosses this gap using neurotransmitters, rather than using electrical impulses. One neurone releases neurotransmitters into the synapse. These diffuse across the gap and make the other neurone transmit an electrical impulse. A summary of information flow, from receptor to effector. Receptors are a group of specialised cells, able to detect a change in environment (stimulus) and produce electrical impulses in response. Sense organs include the skin (touch, temperature), tongue (chemicals), nose (chemicals), eyes, ears. Effectors produce a response to the detected stimulus, such as: a muscle contracting to move an arm; muscle squeezing saliva from the salivary gland; a gland releasing a hormone into the blood.