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Control and Coordination


Animals and Plants show movement with change in environment. Any change in our environment is associated with movement that may be voluntary or involuntary. This movement is a result of coordination and control between different organs and upon analysis of the environment.

In multi-cellular organisms this coordination is done by specialized tissues.

Coordination System in Animals - Nervous System

The control and coordination in animals is done by nervous and muscle tissue.

All information from our environment is detected by special tips of some nerve cells or receptors which are located on our sense organs such as tongue (gustatory), nose (olfactory), optical nerve, auditory nerve etc.

How does information travel?

Information is received by dendrites in the nerve cell. A chemical reactions sets off an impulse This impulse travels from cell body to axon These chemicals cross the gap called 'Synapse' and are passed to the next Neuron

A similar synapses finally allows delivery of such impulses from neurons to other cells,

such as muscles cells or gland.

Because nervous system has to transfer information from one part of body to another, our body has very large network of neurons.

Reflex Actions

Reflex Action is sudden action in response to something in the environment. We do something without thinking about it, or without feeling in control of our reactions.

Thinking involves creation of electrical impulses and is a complex activity that takes place in the brain. It involves complicated interaction of many neurons and impulses from various parts of the body and takes place in front part of the brain. This process may take a lot of time and can lead to delay in our actions in response to sudden changes around us.

Reflex Arc:

To reduce this time, the nerves that detect heat were to be connected to the nerves that move muscles in a simpler way. Such a connection is commonly called a reflex arc.

Simple organisms do not have complex and specialized organs for coordination and

they rely on reflex action to show movement with change in environment.

The closest point for all nerves to meet is at Spinal Cord.

Human Brain

Thinking is a complex process and requires a wide network or nervous system that generates electrical impulses to changes in environment. These signals are passed onto muscles which change their shape due to changing configuration of chemicals and proteins in them.

The Brain and the Spinal Cord constitute the central nervous system. They receive information from all parts of the body and process it for further action.

The peripheral nervous system consists of cranial nerves originating from brain

(Cranium) and spinal nerves originating from Spinal Cord.

They help in communication between central nervous system and the peripheral

nervous system.

Since this network is a sensitive and complex system, it requires protection.

  • The Brain is protected by bony structure called skull which is filled with a liquid gel like component that helps in absorption of shocks.

  • The Spinal Cord is protected by Vertebral column of Backbone

Coordination System in Plants

Plants do not have a nervous system or muscles for control and coordination. The control and coordination in plants is due to presence of electrical impulses.

Plant cells change shape by changing the amount of water in them, resulting in swelling or shrinking, and therefore in changing shapes.

Two types of movement:

  1. Dependent on Growth

  2. External Stimulus

Movement Due To Growth

The tendrils in pea plant curl up as they grow. They are sensitive to touch and wound themselves around any support they find.

The part away from contact grows faster resulting in turning of the tendrils.

The movement could be due to various external factors. The movement of plants could be in the direction of stimulus or away from it depending upon the chemicals and hormones present.

Movements Due To Stimulus

1. Light - Phototropic Movement

(Part away from light grows faster due

to presence of chemicals in that area)

2. Gravity - Geotropic Movement

3. Water - Hydrotropic Movement

4. Chemicals - Chemotropic Movement

The pollen tubes grow towards the ovules due to presence of chemicals that results in such a growth.

What are Tropism? And types of Tropism


For fast response to change in external environment, the transfer of signals should also be fast. While electrical impulses are good at transfer of signals, there are some limitations that make it slow.

Limitations of Electrical Impulses

  • They reach only the cells that are connected to nervous tissue and not each and every cell.

  • It takes some time for regeneration of electrical impulses.

To resolve this, the animal or plant body releases chemicals that diffuse in the body and help in transmission of information. Cells in the body are able to recognize the chemical and the information it carries and can now change accordingly. These chemical compounds that carry information to various cells in a body are called Hormones.

Hormones In Plants




Responsible for Growth of shoot (Found at Tip of Leaves)


Responsible for Growth of Stem


Responsible For Cell Division (Found in Fruits and Seeds)

Abscisic Acid

Inhibits Growth - Causes Wilting of Leaves (Droopy Leaves)

Hormones In Animals

Name of Gland

Hormone Produced




Regulates Metabolism of carbohydrates, proteins and Fats.


Growth Hormone

Stimulate growth in all organs - Responsible for dwarfism or gigantism.



Regulates Blood Sugar Level



Development of male sex organs and characteristics such as change in tone, pubic hair etc.



Development of female sex organs and characteristics such as regulation of menstrual cycle etc.



Increasing Heart beat thus increasing flow of oxygen. Diverts blood from skin and digestive system to skeletal muscles to provide strength. Breathing Rate Increases due to fast contraction and relaxation of diaphragm and rib muscles.

Some Important Points:

  • Hormones in animals are a part of Endocrine System. They have to be release in accurate quantities and this is regulated by the brain.

  • Hypothalamus in brain is responsible of releasing of hormones from pituitary gland that helps in growth.

  • Iodine is required for production of thyroxine - Low iodine causes Goiter (Swollen Necks)

  • Adrenal Glands are located above kidneys


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