Flashcards · Biology · The Nervous System
Reflex Arcs and Reaction Times
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What is a reflex action?
A fast, automatic response to a stimulus that does not involve conscious thought.
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What is a reflex arc?
The pathway of neurones that carries an impulse in a reflex, from receptor to effector.
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Name the parts of a reflex arc in order.
Receptor, sensory neurone, relay neurone, motor neurone, effector.
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Where is the relay neurone in a spinal reflex?
In the spinal cord, in the central nervous system.
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How many synapses are in a simple reflex arc?
Two: one between the sensory and relay neurone, and one between the relay and motor neurone.
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Why are reflexes quick?
Short pathway, few synapses and no conscious thought.
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Why are reflexes protective?
They move the body away from danger before damage is done.
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Give an example of a reflex action.
Pulling the hand away from a hot object, blinking or the pupil getting smaller in bright light.
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What is a voluntary action?
An action that is controlled by conscious thought.
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Which part of the brain is used in voluntary actions?
The cerebral hemispheres.
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What is reaction time?
The time between a stimulus and a response.
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In the ruler drop test, what does a longer distance mean?
A slower reaction time.
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Why should the ruler drop test be repeated?
To calculate a mean and reduce the effect of random errors.
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Name two variables to control in a reaction time test.
The same person and hand, and the same starting position of the ruler.
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Why might a person's reaction time get faster with repeated tries?
Practice improves the reaction, so results change for a reason other than the variable being tested.
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True or false: a person decides to pull away from a hot plate.
False. It is a reflex, and the impulse passes through the spinal cord without conscious thought.