nervous system

•  Nervous System - is a specialised network of cells in the human body and is our primary internal communication system. It is based on electrical and chemical signals whereas the endocrine system is based on hormones. The nervous system has two main functions; to collect, process and respond to information in the environment and to coordinate the working of different organs and cells in the body. The nervous system is divided into two subsystems; the central nervous system and the peripheral nervous system.
• The PNS is subdivided into the:

  Autonomic nervous system (ANS): governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses. It is further divided into the sympathetic branch and the parasympathetic branch of this nervous system.

  Sympathetic branch: is activated during stress (flight or flight).

  Parasympathetic branch: returns the body to its normal resting state (rest and digest).
• Peripheral nervous system (PNS) sends information to the CNS from the outside world, and transmits messages from the CNS to muscles and glands in the body.
• Somatic nervous system (SNS) transmits information from receptor cells in the sense organs to the CNS. It also receives information from the CNS that directs muscles to act.
• CNS: The brain is the centre of all conscious awareness and is divided into two hemispheres.  The brain’s outer layer, the cerebral cortex, is highly developed in humans and is what distinguishes our higher mental functions from those of animals. It picks up stimuli in the environment, which starts the thinking/reacting process.

  The spinal cord is an extension of the brain. It passes messages to and from the brain and connects nerves to the PNS. It is also responsible for reflex actions such as pulling your hand away from a hot plate.