Reflexes

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Human actions can either be conscious or unconscious. Conscious actions use the brain to process information and determine an appropriate response.

Unconscious actions (reflexes) require no thought. Blinking, knee jerk and pupil dilation or contraction are all forms of reflexes.

Reflexes require little to no thought and are known as automatic responses, and may only require two or three neurons

A reflex is a rapid unconscious response to a stimulus.

The reflex arc consists of a receptor neuron sending a message to the Co-ordinating centre (spinal cord) then the signal continues to an effector (body part which responds i.e. muscle). This is shown in the animation to the left.

Once the signal gets to the spinal cord it is split, one signal will go to the affecter while another goes to the brain, alerting you of pain.

Activity

Test your reflexes:

In pairs have one person hold a ruler and another person place their index finger and thumb 7 cm from the top. Without warning drop the ruler. You should find that it is near impossible for the other person to catch the ruler.
Again try and catch the ruler, but this time have the person trying to catch the ruler at the bottom. Measure how long it takes for them to catch the ruler by the amount of cm past.

Break the students up into groups: Musicians, athletes, gamers and other.

Which groups do you expect to have the fastest reactions and why?

Neurons talking

Have all the students stand in a circle and placing one hand on each others shoulder.
Start by squeezing one persons shoulder, that person will squeeze the next persons shoulder and so on until they complete a circle.
Time how long it takes to complete the circle.
Do this 3 times and get an average time.
Next get them to let go of the shoulder and grab the persons ankle.
Again squeeze the persons ankle to start
Time how long it takes to complete the circle.
Do this 3 times and get an average time.

What did you notice?

Why might one be faster than the other?

Is this a reflex?