Fig. 1 shows a mountain rescue volunteer after carrying equipment uphill on a cold island. Sensors in the skin and in the blood detect a fall in body temper...
Question 1 Report
Fig. 1 shows a mountain rescue volunteer after carrying equipment uphill on a cold island. Sensors in the skin and in the blood detect a fall in body temperature. The thermoregulatory centre in the brain coordinates several responses. Blood vessels near the skin become narrower, skeletal muscles contract repeatedly and hairs on the skin may rise. These changes reduce heat loss or increase heat production so that enzyme activity in body cells remains close to normal.
(a) Identify the brain region that coordinates body temperature. [1]
(b) Identify the response shown by the blood vessel at A. [1]
(c) Explain how response A reduces heat transfer from the body surface. [3]
(d) Explain how the response labelled B helps increase body temperature. [2]
(e) Use Fig. 1 to describe the negative feedback sequence when body temperature falls below its normal value. [4]
(f) Calculate the decrease in body temperature if the volunteer’s temperature changes from 37.0 degrees C to 35.6 degrees C. [2]
(g) Suggest one reason why the volunteer should be given warm, sugary water only if they are fully conscious. [1]
Answer Details
(a) Hypothalamus [1] (b) Vasoconstriction [1] (c) Arterioles / blood vessels near the skin narrow [1]; less warm blood flows close to the skin surface [1]; less heat is lost to the surroundings by radiation / convection [1] (d) Muscles contract repeatedly [1]; respiration in muscle cells releases energy as heat [1] (e) Temperature receptors detect a decrease below normal [1]; impulses are sent to the hypothalamus [1]; hypothalamus sends impulses to effectors such as blood vessels and muscles [1]; responses raise temperature towards normal and then reduce/stop [1] (f) 37.0 - 35.6 [1] = 1.4 degrees C [1] (g) An unconscious person may be unable to swallow and could choke / inhale the water [1]
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