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Explain Control and Co-ordination?

In animals, the nervous system, hormonal system and muscular system are responsible for control and coordination.

The nervous system enables humans to react to their surroundings and coordinate their behaviour.

Cells called receptors detect stimuli (changes in the environment).  These include:

   receptors in the eyes which are sensitive to light
    receptors in the ears which are sensitive to sound
    receptors in the ears which are sensitive to changes in position and enable us to keep our balance
    receptors on the tongue and in the nose which are sensitive to chemicals and enable us to taste and to smell
    receptors in the skin that are sensitive to touch, pressure, pain and to temperature changes.

Information from receptors passes along cells called neurons (nerve cells) to the brain. These are found in bundles of hundreds or thousands of neurons known as nerves.  This information is processed by the brain which coordinates any response.

 Impulses from a receptor pass along a sensory neuron to the central nervous system.  The central nervous system is made up of the brain and the spinal cord.

At a junction (called a synapse) between a sensory neuron and a relay neuron in the central nervous system, a chemical is released which causes an impulse to be sent along a relay neuron.

A chemical is then released at the synapse between a relay neuron and a motor neuron in the central nervous system, causing impulses to be sent along a motor neuron to the organ (the effector) which brings about the response.  The effector is either a muscle or a gland.  Glands respond by releasing chemical substances (e.g. adrenaline).

For example if you touch a hot object with your hand, a pain receptor in your skin is stimulated.  A nerve impulse passes along a sensory neuron to the central nervous system (in this case the spinal cord).  The message crosses a synapse to a relay neuron and then crosses a second synapse to a motor neuron.  The motor neuron carries the impulse to a muscle in the arm (the effector).  The muscle will then contract to move your hand away from the hot object.  This action is called the response. This chain of events can be summarised as follows:

Stimulus  Receptor  Coordinator  Effector  Response

The coordinator is the central nervous system (brain or spinal cord)


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