Nervous System of the Human Body

Nervous system of the body is so called because it refers to the nerves of the human body. The actual nerves consist of cylinder bundles of fibre stretching from the brain right through the central cord and creating a network system inside the entire body. The nervous system is primarily used to transmit signals between different parts of the body and in effect to coordinate voluntary and involuntary actions made.

Image of the Nervous System

Image of the Nervous System

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Components of the Nervous System:

  1. Brain
  2. Spinal Cord
  3. Peripheral Nerves
  4. Sense Organs

The nervous system is also perhaps one of the most complex systems of the body functions. The three main areas to be considered in this particular system are:

1. CNS – Central Nervous System

The CNS is made up of the chief nerve better known as the spinal cord and the brain. The main role it plays is to get information from the body and then to distribute this information by sending out the right instructions to the rest of the body. It is in fact the decision maker and co-ordinator. There are 43 pairs of nerves which branch from the CNS – 31 from the spinal cord and 12 from the brain.

2. PNS – Peripheral Nervous System

The PNS consists of all the nerves and the wiring system altogether except the brain and spinal cord. Furthermore PNS can be subdivided into two more components known as the Somatic Nervous System and the Autonomic Nervous System. The brain uses the PNS system to communicate with the rest of the body.

The CNS and PNS share some nerves.

3. ANS – Autonomic Nervous System

This system shares with the previous two mentioned. It works automatically, dealing with the heart rate and the blood pressure. Much of the time it keeps us regulated in these areas allowing us to not even be aware of the important work carried out.

Other important parts of the Nervous System:


There are basically 2 types of nerves known as Spinal Nerves and the Cranial Nerves:

  1. Spinal Nerves: There are 31 pairs of spinal nerves and they are connected to the spinal cord.
  2. Cranial Nerves: There are 12 pairs of cranial nerves and they are connected to the brain.

Nervous Tissue:

The 2 types of cells which the nervous system mainly consists of are the Neurons and Neuroglia:

1. Neurons:

A communication system using the transmission of electrochemical signals exists between the nerve cells. The 3 basic types of neurons as classified by the direction they send messages are as follows and known as:

  1. Afferent Neurons: Also known as sensory neurons, so called as they transmit sensory signals from sensory receptors such as the skin, eyes, ears, nose and tongue TOWARDS the central nervous system
  2. Efferent Neurons: Also known as motor neurons and they are responsible for transmitting messages AWAY from the central nervous system to places in the body such as the glands and muscles.
  3. Interneurons: These form a complex network system within the main nervous system and are useful when it comes to combining the work of the afferent and efferent neurons. Specifically they receive information from the afferent neurons as well as directing body function via the efferent neurons.

Another way to classify Neurons is by identifying the number of extensions from the body of the neuron’s cell. There are three types:

  1. Bipolar Neurons
  2. Pseudounipolar Cells
  3. Multipolar Neurons

2. Neuroglia:

Another name for these is glial cells which are also helper cells. Their main task is to surround the neurons and protect them by insulating and feeding them.

Furthermore, the specialised parts of the Neuron are known as Dendrites and Axons. The main differences between the two are as follows:

Axons: Have a smooth surface and specialise in taking information AWAY from the cell body.

Dendrites: Have a rough surface and specialise in bringing information BACK to the cell body.

Some facts about the nervous system:

  • Three main properties of the nervous system are Sensitivity, Conductivity and Responsiveness
  • The nervous tissue is very delicate. It needs a regular supply of blood and physical protection.
  • Repair to this part of the body system can be rather slow as well as being the least understood in medical terms and in fact the least understood of all the body systems.
  • This complex system is so vast that if each nerve of a body were to be laid side by side it would stretch around the world two and half times!

Part of the Human Body Series:Skeletal System of the Human Body |  Muscular System of the Human Body |

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