The human nervous system is complex and highly organized. To understand the functions properly, this lesson needs to be learned step by step. First of all, let us see the terms we need to learn before studying coordination in humans.

What is a stimulus

A change that takes place in the external environment is known as a stimulus. Vision, Sound, Smell, Taste, and Touch are the commonly seen stimuli.

What are sensory organs

Sensory organs are also known as receptors. They sense stimuli. In other words, sensory organs can identify the changes that take place in the external environment. Eyes, Ears, Nose, Tongue, and Skin are the sensory organs that sense stimuli in the external environment.

What is the response – How it is done?

A response is a reaction to a stimulus. It can be mediated by either a muscle or a gland in the human body. Muscle and glands act as effectors. Therefore, we can say that responses are carried out by the effectors.

Let’s see it with an example. Here in this fight eyes see the threat and muscles of the body respond to it with a defense movement. So in this situation, muscles are the effectors.

Here when the dog is chasing the child, the adrenal glands secrete adrenalin to act quickly in the “fight or flight” situation. The adrenal gland acts as the effector in this situation.

What is irritability?

It is the ability to respond to all sorts of stimuli coming from the both external and internal environment.

What is coordination – in simple terms

Coordination in simple words is the proper communication. This proper communication bridges the receptors (sensory organs) and the effectors (muscles or glands).

During coordination messages received from the sensory organs are communicated to the relevant effectors in the human body.

Let’s see a different more complex definition of coordination.

Types of coordination in the human body

Coordination in the human body is done by the nervous system and the endocrine system. The nervous system carries out the nervous coordination whereas the endocrine system carries out chemical coordination.

The nervous system carries out its actions by nerve impulses and neurotransmitters.

The endocrine system carries out chemical coordination by secreting hormones into blood circulation.

This article focuses on nervous coordination.

Neurons – types involved in the coordination

The nervous system consists of billions of neurons. These neurons transmit impulses by a change in their electro-chemical nature.

Neurons can be simply categorized into three;

  • Motor neurons
  • Sensory neurons
  • Interneurons

The neuron is the structural unit of the nervous system.

The central nervous system – classification

The nervous system can be classified as the central nervous system and peripheral nervous system. The central nervous system contains the brain and the spinal cord. The peripheral nervous system is made of 12 pairs of cranial nerves and 31 pairs of spinal nerves.

The brain of the central nervous system contains three parts. They are the cerebrum, cerebellum, and medulla oblongata.

Billions of neurons altogether make the human brain. The human brain is approximately 1/50th of the body weight. The brain is located inside the skull, which provides protection to it.

A cross-section of the brain shows two distinct regions. They are the white matter and the grey matter.

  • Grey matter makes the peripheral region of the brain and it contains cell bodies of the neurons of the brain.
  • White matter makes the inner region of the brain and it contains the myelin sheaths of the neurons of the brain.

This shows a diagrammatic representation of the three main parts of the brain. They are

  • Cerebrum
  • Cerebellum
  • Medulla Oblongata

Cerebrum – features, and functions

The cerebrum has two hemispheres. They are the left hemisphere and the right hemisphere. The cerebrum makes the most amount of the brain and it is highly developed.

The cerebrum has a relatively higher surface area. That is made possible by the convolutions on the surface.

The brain has a lot of distinct functions that make us humans. An interesting fact is that the left hemisphere of the brain controls the right half of the body whereas the right hemisphere of the human brain controls the left side of the body.

The main functions of the cerebrum are;

  • Perceive senses from the sensory organs
  • Identify and interpret the sensory information
  • Store information
  • Higher mental activities (intelligence, learning, thinking)
  • Control voluntary muscle action

Cerebellum – features, and functions

The cerebellum also has two hemispheres, the left hemisphere, and the right hemisphere. The cerebellum is found inferior to the cerebrum.

The cerebellum is also divided into two regions just like the cerebrum. The grey matter forms the outer region and the white matter forms the inner region.

The functions of the cerebellum are mostly related to fine movements and coordination of voluntary muscle contraction. Cerebellum maintains the body balance, controls voluntary muscle activity, and maintains body movements.

Medulla Oblongata – features and functions

This is a bulge-like structure located anterior and inferior to the cerebrum.

The function of the medulla oblongata is to regulate most of the important involuntary functions that are essential for the human body. Some of them are;

  • Regulating heart rate
  • Regulating respiratory rate
  • Control reflexes like vomiting, coughing, and swallowing

Spinal cord

The spinal cord is a tubular structure that runs through the vertebral column. The vertebral column is made of several vertebrae. They provide protection to the spinal cord.

The spinal cord starts inferiorly from the medulla oblongata. In its course in the vertebral column, the spinal cord gives rise to the pairs of spinal nerves that run bilaterally and symmetrically.

Regions in the spinal cord also contain grey matter and white matter.

But this is different from the arrangement in the brain.

In the spinal cord, the white matter lies in the peripheral region, and grey matter lies in the inner region.


Meninges cover the brain and the spinal cord. They provide protection to the central nervous system. Meninges are made of three layers;

  • Outermost layer – Dura
  • Middle layer – Arachnoid
  • Innermost layer – Pia

CSF – The cerebrospinal fluid

This is a special fluid found in the central nervous system for its protection. It is found between meningeal layers (between the pia and the arachnoid layers which is known as the subarachnoid space) and the spaces of the brain. (Ventricles of the human brain – two of them are known as the left and right lateral ventricles, the third ventricle, and the fourth ventricle)

CSF protects the central nervous system by acting as a shock absorber, providing immunity against infective organisms, and regulating the temperature fluctuations in the body.

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Chaleepa Mallawa

Chaleepa is working as a doctor based in Sri Lanka. He has interest in content creation based on health, science, tech and motivation.