Control and Coordination

Lesson

Part 1 — how your body senses a change, sends a message and responds in a fraction of a second.

In this lesson you will

Explain why multicellular organisms need control and coordination
Draw and label a neuron and describe how an impulse crosses a synapse
Distinguish voluntary, involuntary and reflex actions and trace a reflex arc
State the functions of the forebrain, midbrain, hindbrain and spinal cord, and how they are protected

Concept

Why living things need coordination

A stimulus is a change in the surroundings, such as heat, light, sound or touch. Living things respond to stimuli in a controlled way. Control and coordination make sure the right body parts act together, at the right time, in the right amount.

Table of stimuli and the coordinated responses they cause, with the reason each response helps
Stimulus	Response	Why it matters
Hot tava touched	Hand pulled back at once	Prevents a burn
Smell of food	Mouth waters	Prepares for digestion
Bright sunlight	Pupils become smaller	Protects the retina
Ball thrown at you	Hands move to catch it	Needs many muscles to work together

Concept

Receptors: the body’s sensors

Receptors are specialised cells, usually in sense organs, that detect a stimulus and start a message. Each kind of receptor responds to one kind of stimulus.

Table of receptors, the sense organ each is found in and the stimulus each detects
Receptor	Found in	Detects
Photoreceptors	Eye (retina)	Light
Phonoreceptors	Inner ear	Sound
Olfactory receptors	Nose	Smell
Gustatory receptors	Tongue (taste buds)	Taste
Touch and heat receptors	Skin	Touch, pressure, heat, cold, pain

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