Which of the following changes will increase the rate at which a mammalian organism loses body heat to the environment?

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11ecba2d_1316_35ee_a3bf_fdcb61ad07c1_MD0008_00 Heat transfer is the transmission of thermal energy between two objects or systems by processes such as conduction and convection. In conduction, thermal energy passes between two objects (or domains) through molecule-to-molecule contact. During convection, molecules with higher kinetic energy (ie, temperature) move to a domain where molecules have lower kinetic energy. Heat transfer between two objects or regions occurs until the temperature equalizes. The physical dimensions of the transfer interface influence the rate of heat transfer (H) between objects. For example, the rate of heat transfer between two objects connected by a thermal conductor depends on the conductor length (L), conductor area (A), and difference between the temperature of the hotter object (T_H) and the temperature of the cooler object (T_C): 11ecba2d_1316_5cff_a3bf_3bbd37bb557f_MD0008_00 In biological contexts, heat transfer to the environment is facilitated by processes like ventilation (ie, inhalation and exhalation) and the flow of blood through superficial anatomical structures. The regulation of superficial blood flow via vasoconstriction and vasodilation adjusts the quantity of blood flowing near the (typically) cooler ambient air. Therefore, vasoconstriction decreases the rate of conductive heat loss to the environment and vasodilation increases it. Heat transfer to the environment through ventilation occurs through a similar mechanism except that conductive heat transfer to inhaled air is followed by convective heat transfer through exhalation. Therefore, increasing the rate of respiration increases the rate of heat loss to the environment. (Choice A) Vasoconstriction would reduce blood flow to superficial areas and diminish the rate of heat loss to the environment. (Choice B) Replacing ambient air with warmer air would either diminish or reverse the temperature gradient between the organism and the environment, decreasing the rate of heat loss to the environment. (Choice C) Replacing lean muscle mass with superficial fat would increase the thickness of the superficial structures that act as thermal insulators, decreasing the rate of heat loss to the environment. Educational objective: Heat transfer from an organism to the environment can be accomplished by increasing superficial blood flow (enhancing thermal conduction) or by increasing respiration (enhancing conduction and convection).

Which of the Following Changes Will Increase the Rate at Which