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Protect Yourself From Heat Disorders

Why heat disorders occur

Index

The body maintains a balance between heat production and heat loss. Heat disorders can occur when this balance is disrupted. Take a look at the slideshow below for an illustrated guide to the mechanisms involved.

Heat production and heat loss

  • The human body produces heat constantly. (This is called "thermogenesis.")
  • By allowing this heat to escape from the body (heat loss), the body maintains an internal temperature of around 36℃ to 37℃.
  • However, when the body is active, such as during exercise, a lot of heat is produced by the muscles, and body temperature rises.
  • When it is hot out, direct sunlight or reflected heat can result in a rise in body temperature even when the body is not active.
  • When body temperature rises, blood flow at the body's surface (under the skin) increases to make it easier for heat to escape the body.
  • Because blood circulates through the entire body, this temporarily results in an inadequate supply of blood, and blood pressure falls.
  • When this happens, not enough blood gets sent to the brain, resulting in a lack of oxygen reaching the brain, which may cause dizziness or lightheadedness, and loss of consciousness.
  • This is called "heat syncope."
  • Sweating is another way the body allows heat to escape when body temperature rises considerably.
  • If the water that is lost through sweating is not replaced adequately, this can result in dehydration.
  • If the body remains dehydrated, symptoms including generalized malaise, nausea and/or vomiting, and headache may occur.
  • This is called "heat exhaustion."
  • Sweat is made from blood.
  • When sweat evaporates, heat is efficiently lost outside the body, lowering body temperature.
  • Sweat contains electrolytes (ions), and sweating therefore results not only in the loss of water, but also electrolytes.
  • The electrolyte that is most easily lost in sweat is sodium (salt), which is the most common electrolyte in blood.
  • Therefore, if a person drinks only water when sweating, and does not replenish the salt that is being lost, this will result in an inadequate amount of salt in the body.
  • Because salt plays a role in regulating muscle contractions, an insufficiency of salt can result in muscle spasms and cramping.
  • These are called "heat cramps."
  • If this condition persists, the body's mechanisms for regulating body temperature cannot catch up, body temperature will rise, the brain will be affected, and the person may collapse and lose consciousness.
  • This is called "heat stroke," and is extremely dangerous.
  • Replay
First aid for heat disorders
When heat disorders are likely to occur