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1. 1990/I/5b

In an experiment to study the sensitivity of different parts of the skin touch, student X used a felt pen to
mark out an area on a certain part of the skin of student Y as shown in the diagram above. While student Y
was blindfolded, student X used a pin to touch gently every mark on the test region. Student Y would say
'yes' if he felt the touch. The percentage of positive responses (that is, when student Y could feel the touch)
was recorded. The experiment was then repeated on different regions of the skin and the results are
summarized as below :






(i) Which of the tested regions was most sensitive to touch ? (1 mark)
(ii) Why was student Y unable to feel the touch of the pin on some occasions during the experiment ?
(1 mark)
(iii) Describe the nervous pathway that enables student Y to feel the touch and to speak out. (4 marks)
(iv) At one point during the experiment, student X carelessly applied a strong force on the pin and student
Y withdrew his hand immediately.
(1) Name this type of response. (1 mark)
(2) This type of response usually occurs very rapidly. What is the significance of this characteristic ?
(1 mark)
(3) State ANOTHER characteristic of this type of response. (1 mark)







Region of skin Percentage of positive responses
back of hand
palm of hand
fingertip
forearm
50
85
100
75
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2. 1991/I/5ai(1),ii
The diagram below shows the cross section of a human spinal cord and the nervous supply to the arm :

(i) If the hand touches a hot object accidentally, the hand will withdraw from it immediately.
(1) What happens to the effector muscle in this response ? (1 mark)
(ii) Three men (X, Y and Z) were injured in a traffic accident. A doctor found out that their brains were
still functioning normally. He then conducted further test to check if there was any damage to other
parts of their nervous systems.
Man Test(s) conducted with the eyes of the patients
blindfolded
Observations
X Xs finger tip was pricked by a pin X felt the pain but he did not
withdraw his hand
Ys finger tip was pricked by a pin Y could not feel the pain and did not
withdraw his hand
Y
Y was asked to move his hand Y could move his hand
Z Zs finger tip was pricked by a pin Z withdrew his hand but he was
unaware of the touch and the
withdrawal of his hand
Which part of the nervous system was most likely damaged in X, Y and Z respectively ? Explain your
answer in each case. (8 marks)









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3. 1993/I/3ai,iii
Two patterns of response shown by the human body towards stimuli of different nature are outlined below :

(i) Referring to the specific cell types involved, describe the sequence of events that leads to the
withdrawal of the foot. (4 marks)
(iii) With reference to the mechanisms involved, explain why the response in pattern A occurs much
faster than that in pattern B. (2 marks)

4. 1995/I/3b
The diagram below shows the arrangement of some neurones in man:


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(i) Using numbers in the diagram, indicate the pathways of nerve impulses that bring about
(1) the withdrawal reflex of the arm. (1 mark)
(2) the voluntary action of the arm. (1 mark)
(ii) State two differences between reflex actions and voluntary actions. (2 marks)
(iii) For parts A, B and C of the brain, state and explain one role that each plays when a man is riding a
bicycle. (6 marks)

5. 2000/I/2biii
The pupil response to light intensity is a reflex action coordinated by the brain. By means of a flowchart,
show the nervous pathway involved.
(Hint : This nervous pathway is similar to that of a spinal reflex arc.) (3 marks)

6. 2003/I/1av
Which part of the brain controls the breathing rate ? (1 mark)

7. 2003/I/3aii(2-3)with Q
The diagram below shows a section of the human eye :


(ii) (2) State the type of response illustrated by the constriction of B. (1 mark)
(3) The person also puts on his glasses. With regard to the nature of the response, state two ways in
which this action is different from the constriction of B. (2 marks)

8. 2004/I/2c
Irritability is the ability of an organism to respond to an external stimulus. Most cases of irritability work in
the following pattern :

Below are three examples of irritability in humans :
(I) Secretion of saliva when food is ingested
(II) Constriction of pupil under bright light
(III) Running out of the classroom upon hearing the fire alarm
(i) For case I, state the receptor and effector involved. (2 marks)
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(ii) Based on the above pattern, use a flowchart to show the nervous pathway for case II, including the
types of neurones involved. (3 marks)
(iii) (1) Name the region of the brain where the coordinating centre for case III is located. (1 mark)
(2) State two features of the responses controlled by this region. (2 marks)

9. 2006/I/3
The figure below shows a magnetic resonance image of the lateral side of the upper body of a person:

(a) Name structure X and state its function. (2 marks)
(b) What is the importance of structure Z to structure Y? (1 mark)
(c) The diagram below shows the transverse section of structure Y and an outline of the arm:

On the above diagram, draw the reflex arc for the withdrawal reflex of the arm and label the different
components of the reflex arc. (4 marks)








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10. 2008/I/2
The photograph below shows the lateral view of a human brain.

(a) The surface of structure X is highly folded. What is the significance of this feature? (1 mark)
(b) Name structure Y and state one of its functions. (2 marks)
(c) A patient who suffered from a stroke was diagnosed to have part of area A damaged. After the stroke, it
was found that he had difficulty in moving his arm. What is area A? (1 mark)
(d) Area B is located behind area A. What is area B? (1 mark)
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