Fig. 1 shows a section through human skin during a cold morning. A student cycles to school when the air temperature is 5 degrees C. Temperature receptors s...
Question 1 Report
Fig. 1 shows a section through human skin during a cold morning. A student cycles to school when the air temperature is 5 degrees C. Temperature receptors send impulses to the brain, which coordinates responses in the skin and muscles. The skin contains hairs, sweat glands and blood vessels. In cold conditions, homeostasis reduces the rate at which thermal energy is transferred from the blood to the environment. The student's hands may look pale and their arm hairs stand up. If body temperature falls too far, muscles can contract rapidly without producing useful movement. This releases energy from respiration as heat. The diagram is a simplified section and does not show every type of cell.
(a) Describe the change in skin blood vessels in Fig. 1 when the student becomes cold. [1]
(b) Suggest how this change reduces heat loss from the blood. [2]
(c) What is the name of rapid involuntary muscle contraction that warms the body? [1]
(d) Use knowledge of respiration to describe how this contraction raises body temperature. [2]
(e) Describe how the position of hairs can reduce heat loss. [2]
(f) Which organ coordinates these temperature responses? [1]
Answer Details
(a) Skin blood vessels constrict, becoming narrower. [1 mark]
(b) Less blood flows near the skin surface, so less thermal energy is transferred from the blood to the surroundings. [2 marks]
(c) Rapid involuntary muscle contraction is shivering. [1 mark]
(d) During shivering, muscle cells respire more. Energy released by respiration is transferred as heat, raising body temperature. [2 marks]
(e) Hairs stand upright and trap a layer of air near the skin. Air is an insulator, reducing heat loss. [2 marks]
(f) These responses are coordinated by the brain, specifically the hypothalamus. [1 mark]
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