Ans. Coordination Action
A coordination action has five components;
Stimulus -> Receptors -> Coordinator -> Effecter -> Response
i) Stimuli
We can define a stimulus as any change in environment (external and internal), which can provoke a response in organism
Examples
Touch, light etc. are factors that can bring about certain responses in living organisms. These factors are called stimuli.
More examples of stimuli are heat, cold, pressure, sound waves, presence chemicals, microbial infections etc.
ii) Receptors
Stimuli are detected- by special organs, tissues or cells of body. The organ tissue or cells which are specifically built to detect particular type of stimuli , called receptors.
Example
For example sound waves are detected by ears, light is detected by eyes, chemicals in air are detected by nose and so on.
HI) Coordinators
These are the organs that receive information from receptors and messages to particular organs for proper action.
Examples
In nervous coordination, brain and spinal cord are coordinators. They information and send messages through neurons in the form of nerve impulses
In chemical coordination, various endocrine glands play the role of coordinators They receive information in the form of .various chemicals and send messages secreting particular hormones in blood.
iv) Effectors
These are the parts of body which receive messages from coordinators produce particular responses.
Examples
In nervous coordination, neurons carry messages from coordinators (brain < spinal card) to muscles and glands, which act as effectors.
In chemical coordination, particular hormones carry messages from coordinators (endocrine glands) to particular target tissues, which act as effectors. For hormones, nephrons act as effectors. Similarly, bones liver act as effector many hormones.
Response
On receiving the message from coordinators, the effectors perform action.action is called response. Usually, nervous coordination produces immediate short-living responses while chemical coordination produces slowly but living responses. -
Coordination and Control 35
Example
For example, pulling our hand away from something very hot and the movement of the flower of sunflower towards light are responses.