The nervous system and the endocrine system

Nervous system

- A specialised network of cells in the human body and is our primary internal communication system. It is based on electrical and chemical signals. It has two main functions:
To collect, process and respond to information in the environment
To co-ordinate the working of different organs and cells in the body

- It is divided into two subsystems: Central nervous system and peripheral nervous system

The central nervous system (CNS)

- Made up of the brain and spinal cord. The brain is the centre of all conscious awareness. The brain's outer layer, the cerebral cortex, is only 3mm thick and covers the brain. It is only found in mammals. The brain is highly developed in humans and is what distinguishes our higher mental functions from those of other animals. The brain is divided into two hemispheres

The peripheral nervous system (PNS)

- Transmits messages, via millions of neurons (nerve cells), to and from the central nervous system. It is further subdivided into the:
Autonomic nervous system and the somatic nervous system

Autonomic nervous system (ANS)

- Governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal, and stress response. The system operates involuntarily. It has two main divisions:
the sympathetic and parasympathetic nervous systems

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.

The central nervous system (CNS): Spinal cord

- This 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