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Coordination in animals

involves three main components which are receptors, coordinators and effectors as
illustrated in Figure 2.2.

Receptor Coordinator
Stimulus (Sense organ) (CNS)
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Feedback

Effector
Response
(Muscle or gland)

Figure 2.2: Components of coordination in mammals
Stimulus brain or spinal cord and bring about an
This is a change in the external or internal appropriate response. The effectors include:
environment to which an organism responds. Muscles and glands.
Examples of external stimuli are touch, Response
pain, temperature changes, light, smell and This is any change shown by the organism
sound. Internal stimuli include thirst, hunger responding to stimulus. Response may
and pressure. involve the movement of the whole or part
of the organism’s body. This movement can
Receptors be either towards or away from the stimulus.
These are groups of specialised cells that Examples include the quick removal of the
detect the changes in the environment. leg if pricked by a sharp object, or pulling
Examples of receptors are sense organs, the hand away if it accidentally touches a
including the eye, ear, nose, skin and tongue. hot object.

Coordinator Feedback
This is an organ that receives and interprets The animal decides what to do in response
message from the receptors. Coordinators to the stimuli.
include the brain and the spinal cord. A
coordinator uses messages to link activities Activity 2.1:
in the body. The messages received are
called nerve impulses. Investigating ways in which coordination
is brought about
Effectors Materials
These are the cells, organs or organelles Books of the same size and a table
which receive motor impulses from the

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