Home News BIOLOGY FORM THREE TOPIC 3: COORDINATION,

BIOLOGY FORM THREE TOPIC 3: COORDINATION,

TOPIC 3: COORDINATION

In
this topic you will learn about concept of coordination, nervous
coordination inhumans, sense organs, drugs and drug abuse in relation to
nervous coordination, andcoordination in plants.
The Concept of Coordination in Organisms
Explain the concept of coordination in organisms
Coordination
is the working together of the various organs of an organism in a
systematic manner so as to produce a proper response to the stimuli.
Without coordination the body becomes disorderly and it may fail to
function properly.
The Ways in Which Coordination is Brought About
Outline the ways in which coordination is brought about
The
coordination in simple multicellular animals takes place through
nervous systemonly. The control and coordination in higher animals
called vertebrates (including humanbeings) takes place through nervous
system as well as hormonal system called endocrinesystem. Coordination
in plants is under the control of hormones.
All
the living organisms (plants and animals) respond and react to changes
in the environment around them. The changes in the environment to which
the organisms respond and react are called stimuli (singular: stimulus).
The living organisms show response to stimuli such as light, heat,
cold, sound, smell, taste, touch, pressure, pain,water, and force of
gravity, etc. The ability to perceive, interpret and respond to stimuli
is called irritability or sensitivity.
There
are two types of stimuli: external and internal. External stimuli are
associated with the surrounding environment such as wind temperature,
light, pressure, touch, water and gravity. Internal stimuli occur within
the organism, for example, a decrease or an increase in the amount of
water and glucose in the blood.
When
an organism detects a stimulus, it initiates a response. A response is a
behavioural,physiological or muscular activity initiated by a stimulus.
For example, if a man touches a very hot utensil accidentally, he
quickly pulls his hand away from the hot utensil. Here,heat is the
stimulus and the man reacts (responds) by moving his hand away from the
hot utensil. Similarly, when the sun is bright, we close our eyes. In
this case, light is the stimulus and we react by closing our eyes.
Likewise, when the amount of water in the blood drops, the pituitary
gland secretes an anti-diuretic hormone (ADH) which stimulates the
reabsorption of water in the kidneys.
Multicellular
organisms detect stimuli through sense organs called receptors. A
receptor is a sense organ (e.g. eye) or sensory nerve ending (e.g. in
the skin or internal organ) which receives stimuli and sets nervous
impulses. Impulses are electrical transmissions or chemical stimuli that
are sent from the receptor to the coordinating system in the organism.
The organs that respond to the stimuli are called effectors. A
coordinator is an organ (e.g. the brain and spinal cord) that receives
messages from the receptors,translates them and sends the information
back to an effector for action. An effector is a muscle or gland which
receives impulses from nerves, brain or spinal cord and responds to
them. Response is the end-action, such as a muscle contracting to cause
the movement of the arm. The diagram below illustrates the five
components of coordination in mammals.
SHARE