What is Nervous System?

All animals react to changing condition in the environment. In the human body several organs and organ systems perform numerous actions in association with each other. In spite of numerous activities taking place in the body at the same time, the individual behaves as a single unit. How does this happen? How does an individual respond to changes in the environment? All these jobs are done by our nervous system. The nervous system controls and coordinates various functions of the body. In addition to this it makes us aware of the environment. Response to changes in the environment is a function of the nervous system. It helps us to see, hear, feel, think and coordinate our activities.

Autonomic Nervous System

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The nervous system consists of:

  1. Brain
  2. Spinal cord
  3. Nerves

1. Brain:

Brain is the source of what we know about the world. Compared to the brain of other animals, the human brain is the best developed and the most complicated. In an average adult, the brain weighs about 1 kg and 200 grams. It is well protected by a bony skull. Brain consists of three parts. I) brain stem, ii) cerebellum and iii) cerebrum.


The Brain Stem or Medulla: The brain stem is at the bottom of the brain, where it joins the spinal cord. The stem controls the body’s automatic processes, such as heartbeat, breathing, body temperature, blood pressure, digestion, and getting rid of waste.

The Cerebellum: The cerebellum lies at the back of the brain. The cerebellum coordinates movements and controls posture and balance.

The Cerebrum: the cerebrum is the largest part of our brain. It is so large that is must be folded or wrinkled to fit inside the skull. The cerebrum is responsible for our thoughts, emotions and awareness.

2. Spinal Cord:

Spinal cord is a cylindrical cord that runs inside the vertebral column (backbone). It extends vertically downwards from the brain. The backbone surrounds and protects the spinal cord. Thirty-one pairs of nerves branch from the spinal cord, connecting it to every part of the body.

3. Nerves:

A nerve is composed of many fibers enclosed in a sheath (covering). Nerves from a network in the body and connect different parts of the body to brain and spinal cord. They are of two kinds:

  • Sensory nerves: Nerves that conduct messages from different parts of the body like sense organs to the brain are called pain sensory nerves. These nerves conduct sensations like touch, pain, heat, cold, taste, vision and hearing.
  • Motor nerves: Nerves that conduct messages from brain to different parts of the body are called motor nerves. Many of these nerves cause movement of body parts like hands and legs.
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