Exam questions · Biology · The Nervous System
Reflex Arcs and Reaction Times
- 6 exam questions
- 19 marks
- 9 quick checks
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1 State [1 mark]
State what is meant by a reflex action.
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Model answer
A fast, automatic response that does not involve conscious thought.
Mark scheme
- Fast and automatic without thinking — 1 mark
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2 Name [3 marks]
Name the three types of neurone in a reflex arc, in the order that the impulse passes through them.
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Model answer
Sensory neurone, then relay neurone, then motor neurone.
Mark scheme
- Sensory — 1 mark
- Relay — 1 mark
- Motor, in the correct order — 1 mark
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3 Describe [3 marks]
A person touches a hot object and moves their hand away. Describe what the receptor and the effector do in this reflex.
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Model answer
The receptor in the skin detects the heat and starts an electrical impulse, which goes to the sensory neurone. The effector, a muscle in the arm, receives the impulse from the motor neurone and contracts to pull the hand away.
Mark scheme
- Receptor detects the stimulus and starts an impulse — 1 mark
- Effector is a muscle — 1 mark
- It contracts to move the hand away — 1 mark
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4 Explain [3 marks]
Explain why a reflex action is faster than a voluntary action.
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Model answer
In a reflex there are only a few neurones and synapses, so the impulse passes along a short pathway. The impulse travels through the spinal cord and does not have to be processed by the conscious part of the brain. This means there is less delay before the muscle responds.
Mark scheme
- Short pathway / few neurones — 1 mark
- Few synapses, so little delay — 1 mark
- No conscious thought or decision — 1 mark
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5 Calculate [3 marks]
A student catches a ruler five times in a reaction-time test, at 12 cm, 15 cm, 18 cm, 14 cm and 16 cm. Calculate the mean distance. Explain why the student repeated the test.
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Model answer
The total is 12 + 15 + 18 + 14 + 16 = 75 cm, so the mean is 75 divided by 5, which is 15 cm. The test was repeated so that a mean could be calculated, which reduces the effect of random errors and makes the result more reliable.
Mark scheme
- Total of 75 cm — 1 mark
- Mean of 15 cm — 1 mark
- Repeating makes the mean more reliable — 1 mark
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6 Evaluate [6 marks]
A student investigates the effect of caffeine on reaction time using the ruler drop test. Describe how the investigation could be done, and evaluate the method.
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Model answer
The student measures the distance the ruler falls before it is caught, before and after drinking a caffeinated drink. A longer distance means a slower reaction. The variables to control are the same person, the same hand, the same ruler and the same starting position, and the test is repeated and a mean calculated. The method is simple and uses cheap equipment. However, the person dropping the ruler might drop it at different speeds or give clues, and the participant gets better with practice, which can affect the results. Using a computer reaction test would be more precise.
Mark scheme
- Independent variable: caffeine; dependent variable: distance caught — 1 mark
- Describes repeated tests and a mean — 1 mark
- Controls at least two variables — 1 mark
- A strength, such as simple or cheap — 1 mark
- A weakness, such as human error or practice effect — 1 mark
- An improvement, such as a computer test — 1 mark
Quick check
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1
Which of these is an example of a reflex action?
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C: Pulling a hand away from a hot object
Pulling a hand away from something hot is automatic and does not involve conscious thought.
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2
What is the order of the parts in a reflex arc?
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A: Receptor, sensory neurone, relay neurone, motor neurone, effector
The impulse passes from the receptor through sensory, relay and motor neurones to an effector.
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3
Where is the relay neurone in a withdrawal reflex?
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B: In the spinal cord
The relay neurone is in the spinal cord, part of the central nervous system.
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4
Why are reflex actions so fast?
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D: The pathway is short and involves no thinking
The pathway is short, with few synapses and no conscious thought.
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5
What type of effector is used in a withdrawal reflex?
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A: A muscle
A muscle contracts to pull the hand away.
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6
What is the role of the pupil reflex?
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C: To protect the retina from too much light
The pupil gets smaller in bright light so that too much light does not damage the retina.
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7
In the ruler drop test, what does a longer distance mean?
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B: A slower reaction time
A ruler that falls further before being caught shows that the person took longer to react.
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8
A student does the ruler drop test five times and gets 10, 12, 11, 12 and 15 cm. What is the mean distance?
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D: 12 cm
The total is 60 cm, and 60 ÷ 5 = 12 cm.
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9
Why does a person feel pain after their hand has moved away from a hot pan?
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C: The impulse reaches the brain after the reflex has already happened
The reflex pathway goes through the spinal cord, so the muscle responds first. The impulse reaches the brain a moment later, and that is when the pain is felt.