Two systemic effects of heat on the body are

• A. Vasodilation and an increase in metabolic rate
• B. Hypothermia and shivering
• C. Dilated pupils and decreased heart rate
• D. Sweating and vasoconstriction

Answer: (A)

The main idea here is how the body responds to heat on a systemic level. When core temperature rises, the hypothalamus initiates mechanisms to dissipate heat, primarily by increasing blood flow to the skin and boosting heat-loss processes. Vasodilation of skin vessels is the key systemic change because it brings more warm blood to the surface where it can be cooled by the environment. At the same time, body processes can show a rise in metabolic rate as temperature influences the speed of enzymatic reactions and supports the energy demands of cooling mechanisms like sweating and increased circulation.

The other options mix responses that aren’t driven by heat. Shivering is a reaction to cold, not heat. Dilated pupils and decreased heart rate aren’t typical systemic heat responses. Sweating is a heat-loss mechanism, but vasoconstriction would counter heat loss, not support it. So the combination of vasodilation and an increase in metabolic rate best captures the body’s systemic response to heat.