MEDICAL PHYSIOLOGY

Detailed explanation-1: -These flat hairs increase the flow of air next to the skin increasing heat loss by convection. When environmental temperature is above core body temperature, sweating is the only physiological way for humans to lose heat. Arteriolar vasodilation occurs.

Detailed explanation-2: -The hair on the body also affects the regulation of body temperature as erect hair can trap a layer of heat close to the skin.

Detailed explanation-3: -On most days, the hypothalamus reacts to increases in outdoor temperature by sending messages to the blood vessels, telling them to dilate. This sends warm blood, fluids and salts to the skin, setting off the process of evaporation.

Detailed explanation-4: -The arrector pili muscles contract (piloerection) and lift the hair follicles upright. This makes the hairs stand on end, which acts as an insulating layer, trapping heat.

Detailed explanation-5: -When too warm: the hair erector muscle relaxes, lowering the hair. a thin insulating layer of air is trapped above the skin. more heat is lost to the environment.