Reaction Time
Q1.
(a)     Diagram 1 shows the neurones and parts of the body involved in a response to touching a hot object.
Diagram 1
 
A neurone is a nerve cell. Neurones carry impulses around the body.
(i)      Draw a ring around the correct answer to complete each sentence.
 
Neurone A is a	motor neurone.
relay neurone.
sensory neurone.	
 
At point Y there is a tiny gap between two neurones called	an effector.
a receptor.
a synapse.	
(2)
(ii)     The hand touches a hot object. An impulse travels through the nervous system to the muscle (point X). The muscle moves the hand away from the hot object.
What does the muscle do to move the hand away from the hot object?
Tick () one box.
contract		
relax		
stretch		
(1)
(iii)    The action described in part (a) (ii) is a reflex action.
How can you tell that this action is not a conscious action?
Use information from the diagram.
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(1)
(iv)    Reflex actions like this are useful.
Explain why.
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(2)
(b)     Some students investigated the effect of caffeine on a person’s reaction time.
The students used the following steps.
1. One student held a ruler just above a second student’s hand, as shown in Diagram 2.
Diagram 2
 
2. The student let go of the ruler. The second student caught it as soon as possible, as shown in Diagram 3.
Diagram 3
 
3. The students repeated this experiment seven more times.
4. The student catching the ruler then drank a cup of strong coffee.
    Coffee contains caffeine.
5. Fifteen minutes after drinking the coffee the students repeated steps 1 to 3.
Table 1 and Table 2 show the students’ results.
 
Table 1	 	Table 2	
Distance ruler fell
before it was caught
in cm	 	Distance ruler fell
before it was caught
in cm	
Before drinking coffee	 	After drinking coffee	
18	 	8	
21	 	13	
25	 	11	
15	 	17	
19	 	10	
16	 	14	
12	 	13	
21	 	13	
Mean = 18.4	 	Mean = 12.4	
(i)      The students used the reading on the ruler as a measure of the reaction time.
What do the results show about the effect of caffeine on reaction time?
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(1)
(ii)     Look carefully at all the data in Table 1 and Table 2.
Using the data in Table 1 and Table 2, give one reason why a scientist may not accept your conclusion in part (b) (i).
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(1)
(iii)    How could the students improve their investigation?
Suggest two ways.
1. ____________________________________________________________
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2. ____________________________________________________________
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(2)
(Total 10 marks)