Reaction times

Your nervous system is made of your central nervous system (called the CNS) and the peripheral nervous system. Nerve cells are also called Neurones. A nerve is a group of neurones. Simple reflexes use only 2-3 nerve cells and this system is called the reflex arc and does not require processing by the brain. Simple reflexes like your reaction to move away from pain are very fast.

Reaction time, not to be confused with reflexes, is the time it takes for you to respond to a stimulus. Usually this is a visual or auditory (sound) stimulus. In schools, we use the ruler drop test as it is low cost and does not require a ruler.

The experiment

• The dependent variable is the reaction time. This is measured using a calibrated scale on the ruler which converts distance to time.
• The independent variable can be a range of factors, such as your dominant vs subordinate hand (left vs right), male vs female, drinking caffeine or not.
• There are several variables that need to be controlled. These trials involve humans. Any trials involving humans always need more repeats (ie 10) and you need to consider tiredness, previous practice, gender, age, other stimulants that may have been taken etc.
• The most common errors are that all of the variables are not controlled because you are using humans. The experiment may not be Valid.

Groups of nerve cells called neurones

A synapse. Between this gap, chemicals (called Neurotransmitters) diffuse from one side to the other side to help pass a nerve signal.

Caffeine is a stimulant because it causes an decrease in reaction times (makes you react faster)

Alcohol is a depressant because it slows you reaction times (makes you react slower)