Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 66

As core temperature begins to rise (e.g. following a bout of intense exercise) temperature sensors (thermoreceptors) detect this rise and feed information to the hypothalamus. This region of the brain functions as the thermoregulatory control centre initiating the physiological changes that will lower core temperature towards the set point of 37°C. When the core temperature is high, the hypothalamus increases blood flow to the skin by initiating the vasodilation of blood vessels in the dermis. Since the skin has a large surface area of over 1.5–2 square metres, this allows rapid heat loss through conduction, convection and radiation. If the core temperature remains high then eccrine sweat glands in the skin can be activated. These produce a thin watery sweat that will evaporate at the skin’s surface to allow rapid cooling; however, if water intake is not maintained then prolonged sweating can lead to dehydration (Chapter 1).

If the core temperature cannot be reduced, this can lead to hyperthermia (remember, hyper means high), and this is commonly seen in heatstroke, for example in endurance athletes. Heatstroke is a life-threatening medical emergency since having a persistently high core temperature reduces the activity of the enzymes essential for cellular metabolism and energy release. It is treated initially by cooling the body by whatever means are available; initially this will involve removing layers of clothing and immersing the body in cool water or using ice packs.