.2 The human nervous system

• The nervous system enables humans to react to their surroundings and to coordinate their behaviour.
• Information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS). The CNS is the brain and spinal cord. The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.
• stimulus - receptor - coordinator - effector - response
• Reflex actions are automatic and rapid; they do not involve the conscious part of the brain.