The Nervous System

The nervous system helps animals to survive by responding to stimuli. Receptor cells detect stimuli and the sensory neurons then carry messages to the central nervous system.

Neurons send fast electrical impulses to other cells along the axon, a long fibre. Axons are coated by an electrically insulating myelin sheath. Neurons pass messages to each other by releasing chemicals called neurotransmitters into the synapse. Poisons and drugs can interfere with this process.

The CNS consists of the brain and spinal cord in vertebrates and it makes decisions about how to respond to a stimulus. Motor neurons carry messages from the CNS to effectors e.g. muscles and glands. The sensory and motor neurons make up the peripheral nervous system.