1. 1
   A gardener grasps a rose stem and a thorn pierces the skin of her fingertip. Her hand is pulled away from the stem before she is aware of any pain. About half a second later she feels a sharp pain in her finger and says "ouch".

   (a)

   In the reflex arc that withdrew the hand, where is the interneuron located?

   [1 mark]

   • AIn the grey matter of the spinal cord
   • BIn the white matter of the spinal cord
   • CIn the cerebellum
   • DIn the skin of the fingertip, next to the pain receptor

   (b)

   What is the effector in this reflex?

   [1 mark]

   • AThe free nerve ending of the sensory neuron in the fingertip
   • BThe motor neuron leaving the spinal cord
   • CSkeletal muscle in the arm
   • DSmooth muscle in the wall of the gut

   (c)

   Explain why her hand was withdrawn before she was aware of the pain.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A man wearing a heart-rate monitor has been lying on a bed for ten minutes. He stands up quickly. Blood pressure in his carotid arteries falls briefly, and within a few seconds his heart rate rises from 62 to 78 beats per minute, after which his blood pressure returns to normal.

   (a)

   Where are the receptors that detected the fall in blood pressure?

   [1 mark]

   • AIn the medulla oblongata
   • BIn the walls of the aorta and carotid arteries
   • CIn the sinoatrial node of the heart
   • DIn the pineal gland

   (b)

   Which part of the brain coordinated the change in heart rate?

   [1 mark]

   • ACerebellum
   • BCerebral hemispheres
   • CPituitary gland
   • DMedulla oblongata

   (c)

   Calculate the percentage increase in heart rate, and suggest how this increase helps to restore blood pressure.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Healthy volunteers at rest breathed air containing different percentages of carbon dioxide for 10 minutes each. At the end of each period their ventilation (volume of air breathed per minute) and the pH of their arterial blood were measured. With 0.04 % carbon dioxide (normal air): ventilation 7.5 dm³ min⁻¹, blood pH 7.40. With 2 % carbon dioxide: 11.0 dm³ min⁻¹, pH 7.38. With 4 % carbon dioxide: 20.5 dm³ min⁻¹, pH 7.35. With 6 % carbon dioxide: 38.0 dm³ min⁻¹, pH 7.31.

   (a)

   Explain why the pH of arterial blood fell as the percentage of carbon dioxide in the inhaled air increased.

   [3 marks]

   (b)

   Analyse the data to explain how the body responds to the increase in inhaled carbon dioxide, and why the change in pH is so small.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A cheetah (Acinonyx jubatus) watches a herd of gazelles, then stalks slowly towards one animal, keeping low in the grass. When it is about 50 m away it accelerates to a sprint of up to 100 km h⁻¹, turning sharply as the gazelle swerves. The chase rarely lasts more than 30 seconds. Just before and during the chase, the cheetah's adrenal glands secrete epinephrine (adrenaline). After a successful hunt, the meat it eats passes slowly along its gut over the next day.

   (a)

   Compare and contrast the ways in which the nervous system and the endocrine system send messages in the cheetah during the hunt, with reference to epinephrine.

   [6 marks]

   (b)

   Discuss the view that the cheetah's ability to catch prey is an emergent property that depends on the integration of its body systems rather than on any single system.

   [6 marks]

   Total for question 4: 12 marks

End of questions