What are the effects of heat and cold?

At the end of this unit, you should be able to, for each of heat exhaustion, heat stroke, hypothermia and frostbite:

  1. Explain what it is
  2. List possible causes
  3. Recognise signs and symptoms
  4. Describe appropriate treatment
  5. Demonstrate an appropriate attitude towards the casualty (eg. reassuring, caring, firm)
  6. List possible ways to prevent it

What are the effects of heat and cold?

Most of the time we are able to maintain a constant body temperature even though the temperature around us may change quite a lot. Th e body normally keeps its temperature at between 36oC – 38oC (96.8oF – 100.4oF). It does this by balancing the heat made by or taken into the body and the heat lost by the body. Heat is made by the body by the changing of food into energy and by muscle activity (either through exercise or shivering). Heat is also taken in from the sun, or by taking hot food and drink, or by contact with hot objects. Heat is lost through the breath or body surface (if the environment outside is cooler than the body).

The body balances its temperature by saving or losing heat:

When the outside temperature is hot, the body loses heat by:

  1. Making the blood vessels near the skin bigger, so more heat can pass out
  2. Sweating more
  3. Breathing more quickly and more deeply

When the outside temperature is cold, the body saves heat by:

  1. Making the blood vessels near the skin smaller to keep the heat in
  2. Sweating less
  3. Making the hairs on the body stand up to keep warm air in next to the skin

Heat

Certain situations make it difficult for the body to lose heat. These are:

When the temperature outside is very hot (because it becomes more difficult for the body to lose heat by giving off heat)

When there is high humidity (i.e. moisture in the air) (because the moisture in the air makes it difficult to lose heat by sweating)

During very hard exercise (because doing the exercise makes so much heat). When these situations happen (especially if they happen together), the body may not be able to lose heat fast enough, and two general conditions may develop – heat exhaustion or heat stroke.

Cold

In certain situations, the body may not be able to keep enough heat, or make enough heat. Two conditions may develop – hypothermia and frostbite.