1. 1
   A student learns that the human body keeps internal conditions such as blood glucose concentration and body temperature close to a set point using negative feedback mechanisms involving both the nervous system and hormones.

   (a)

   Homeostasis is the maintenance of a constant internal environment. Which term describes the value around which a variable such as body temperature or blood glucose concentration is regulated?

   [1 mark]

   • AA set point
   • BA gradient
   • CA trophic level
   • DAn allele

   (b)

   If blood glucose concentration rises above the set point, the body responds by lowering it back down. What is this type of control mechanism called?

   [1 mark]

   • APositive feedback
   • BNegative feedback
   • CActive transport
   • DOsmosis

   (c)

   Explain what is meant by negative feedback, using blood glucose concentration as an example.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   After eating a large meal rich in carbohydrates, a person's blood glucose concentration rises sharply. Several hours later, after not eating for some time, their blood glucose concentration begins to fall, and the liver responds to hormonal signals to correct both changes.

   (a)

   After eating a large meal, a person's blood glucose concentration rises. Which organ secretes the hormone that lowers it back towards normal?

   [1 mark]

   • AThe liver
   • BThe adrenal gland
   • CThe kidney
   • DThe pancreas

   (b)

   Several hours after the meal, blood glucose concentration begins to fall, and glucagon is secreted. What effect does glucagon have on the liver?

   [1 mark]

   • AIt stimulates the liver to produce bile
   • BIt stimulates the liver to convert glucose into glycogen for storage
   • CIt stimulates the liver to convert stored glycogen into glucose, releasing it into the blood
   • DIt stimulates the liver to deaminate amino acids

   (c)

   Describe how the liver responds to insulin when blood glucose concentration is too high.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An athlete exercises hard in hot weather, sweating heavily with flushed red skin, and later that evening feels cold, starts to shiver and notices goosebumps as the hairs on their skin stand up.

   (a)

   An athlete exercises hard in hot weather and starts to sweat heavily, with visibly flushed, red skin. Describe how sweating and the widening of blood vessels near the skin surface (vasodilation) help to cool the body down.

   [3 marks]

   (b)

   That evening, the athlete feels cold, begins to shiver and the hairs on their skin stand upright, giving 'goosebumps'. Describe how shivering and the erection of hairs help to maintain body temperature in the cold, and explain the role of vasoconstriction in this response.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A patient is monitored over a 24-hour period, during which their blood glucose concentration and core body temperature are both recorded. Blood glucose rises after meals and falls between meals but always returns towards a set point, while body temperature stays close to 37 degrees Celsius despite the patient moving between a cold room and a warm room.

   (a)

   A patient is monitored over a 24-hour period. Their blood glucose concentration rises after each meal and falls between meals, yet always returns towards a similar set point within a couple of hours. Explain, using the concept of negative feedback and the roles of insulin and glucagon, how the body maintains blood glucose concentration close to this set point throughout the day.

   [6 marks]

   (b)

   During the same 24-hour period, the patient's core body temperature stays close to 37 degrees Celsius even though they move between a cold room and a warm room. Explain, using the concept of negative feedback, how the brain and skin work together to keep body temperature close to this set point in both environments.

   [6 marks]

   Total for question 4: 12 marks

End of questions