Reflex Actions

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Reflex Actions

- Nervous system- lets you take information about the world around you and respond in the right way

- When you touch something hot,or sharp, you pull your hand back before you feel the pain.

-If something comes near your face, you blink. Automatic responses like these are known as REFLEXES 

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How do your reflexes work

-Reflex actions involve three types of neurones:

-Sensory neurones 

-Motor neurones

-Relay neurones-> connect a sensory neurone and a motor neurone. Find relay neurones in the CNS, often in the spinal cord. 

-An electrical impulse passes from the sensory receptor along the sensory neurone to the CNS 

-It then passes along a relay neurone and straight back along a motor neurone 

-From there the impulse arrives at the effector organ (usually a muscle in a reflex)

- We call this a REFLEX ACTION

-The key point in a reflex arc is that the impulse bypasses the conscious areas of your brain

-The result is that the time between the stimulus and the reflex action is a short as possible  

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How synapses work

-Your nerves are not joined up directly to each other 

-There are junctions between them called SYNAPSES 

-The electrical impulses travelling along your neurones have to cross these synapses but they cannot leap the gap 

What would happen if someone touched a hot object;

-When they touch it a receptor in their skin is stimuated 

-An electrical message passes along a sensory neurone to the CNS

-When a impulse from the sensory neurone arrives in the synapse with the relay neurone, a chemical message is released 

-This crosses the synapse to the relay neurone and sets off an electrical impulse that travels along the relay neurone 

-When the impulse reaches the synapse between the relay neurone and motor neurone returning to the arm, another chemical message is released 

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How synapses work 2

-This crosses the synapse and starts an electrical impulse travelling down the motor neurone

-When the impulse reaches the organ (effector), it is stimulated to respond 

-In a reflex action the co-ordinator is a relay neurone either in the spinal cord or in the unconscious areas of the brain 

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