Cambridge O Level Biology · Syllabus 5090 · Coordination and Control
Hair Erector Muscle
What is Hair Erector Muscle?
A small muscle attached to a hair follicle in the skin. When it contracts, the hair is pulled upright and a layer of air is trapped next to the skin, reducing heat loss. When it relaxes, the hair lies flatter and less insulating air is trapped. The effect is far more important in furry mammals than in humans.
This definition is part of the Coordination and Control chapter in Cambridge O Level Biology.
Questions students ask about Hair Erector Muscle
How does the body cool itself down?
Sweat glands produce more sweat, which spreads over the skin and evaporates, transferring thermal energy away from the body. The arterioles supplying the surface capillaries dilate, so more warm blood flows near the skin and more heat is transferred to the surroundings. The hair erector muscles relax, so the hairs lie flatter and trap less insulating air.
How does the body warm itself up?
Sweating is reduced, so less energy is lost by evaporation. The arterioles supplying the surface capillaries constrict, so less warm blood flows near the skin. Skeletal muscles shiver, which increases respiration in those muscles and releases more energy as heat. The hair erector muscles contract, raising the hairs so that an insulating layer of air is trapped. Fatty tissue beneath the skin insulates at all times.