What happens to muscle around arterioles when the temperature drops?

When the temperature drops, the body responds in ways that help to conserve heat and maintain core temperature. In the case of arterioles, the muscle surrounding them, known as smooth muscle, reacts by undergoing vasoconstriction. This process narrows the diameter of the blood vessels, which reduces blood flow to the skin and extremities.

Vasoconstriction serves several purposes: it helps to minimize heat loss from the body's surface by limiting blood flow to those areas, which might otherwise dissipate heat into the cooler environment. By constricting these arterioles, the body prioritizes blood flow to vital organs, ensuring they receive an adequate blood supply even in cold conditions. This mechanism is part of the body's thermoregulatory system, which works to maintain homeostasis in response to temperature changes.

In contrast, the other options would not occur under cold conditions. For instance, vasodilation would increase blood flow to the surface of the skin, promoting heat loss, which is counterproductive when trying to preserve body temperature in cold environments. Therefore, the response of muscle around arterioles in reaction to cold temperatures is accurately described by the occurrence of vasoconstriction.