Which physiological change is commonly associated with a fever?

Increased heart rate is commonly associated with a fever due to the body’s response to infection or illness. When a fever occurs, it is typically a sign that the immune system is active and working to combat pathogens. This heightened state of immune activity demands more energy and oxygen, which prompts the cardiovascular system to respond by increasing the heart rate. An elevated heart rate helps facilitate the delivery of oxygen and nutrients to various tissues and organs that are engaged in the immune response.

Additionally, the increase in heart rate is also linked to the rise in body temperature that characterizes a fever. As the body temperature rises, metabolic processes are enhanced, requiring better circulation to meet the elevated demands.

In contrast, the other options reflect physiological responses that do not align with the body's reactions during a fever. Vasodilation, while sometimes occurring in the context of fever, is more associated with the initial stages of an inflammatory response rather than a direct hallmark of fever. Decreased respiration rate is not typical during a fever, as increased energy demands usually lead to higher respiratory rates to meet oxygen needs. Lastly, a lowered metabolic rate conflicts with the elevated metabolic processes associated with fever, where the body ramps up its energy expenditure to fight off the infection.