The Nervous System

Your brain controls just about everything you do including all the activities that are going on inside your body. All such actions have to be properly timed and coordinated, which is done by the nervous system and the hormonal system. The nervous system is an organ system containing a network of specialized cells called neurones that coordinate the actions of an animal/mammal and transmit signals between different parts of the body. The nervous system is divided into two main systems, the central nervous system and the peripheral nervous system.The central nervous system is comprised of the brain and spiral cord, which is located in and protected by the skull and the vertebral column.  The main job is to get the information from the body and send out instructions. The peripheral nervous system is make up of all the nerves which transmits the messages from the brain to the rest of the body. The peripheral nervous system connects the central nervous system to sensory organs. Examples of sensory organs are the human eye, ears, muscles, blood vessels and glands.

Neurones are the basic building blocks of the nervous system. These cells are the information-processing units of the brain responsible for receiving and transmitting information. Each part of the neurone plays a role in the communication of information throughout the body.


A Neurone has three parts; the cell body, the axon and the dendrites The cell body contains a well defined nucleus surrounded by a granular cytoplasm. The cell body is also known as a perikaryon.

Dendrites are branched cytoplasmic projections of the cell body. They are for receiving impulses from the axon of another neurone.

The axon is a long process of neurone cell body. The axon is specialized to carry message and has the ability to contact 1000 other neurones but only if it has enough branches. Axons are covered by a protective layer of a white, insulating sheath called myelin sheath. The myelin sheath shows gaps throughout the length, which are called nodes of ranvier. The end of the axons have swollen bulbs called axon terminals that store certain chemicals called neurotransmitters.

There are three different types of neurones.

 Sensory neurones: carry impulses from sense organs to the central nervous system.

Motor neurones: carry impulses from the central nervous system to muscles or glands of our body.

Interneurones: connect various neurones within the brain and spinal cord. It carries information between the motor and sensory neurones.

The brain is the main component of the nervous system. The brain contains around a thousand billion neurones. The brain is protected by three membranes coverings called:

 Meninges; continue through to the spinal cord.

Dura Mater; which is the fabarus membrane (outer layer).

Arachnoid; thin, delicate, gives web like cushion (middle layer).

Pia Mater; highly vascular, richly supplied with blood (inner layer).

The space between these membranes is filed with the cerebrospinal fluid. It acts like a cushion to protect the brain from shocks. The fluid also fills the spaces inside the brain and the central canal of the spinal cord.