Your body works best when its internal temperature stays close to 37°C, or 98.6°F. This steady balance is called homeostasis, and it helps enzymes, cells, and organs function properly. The main control center is the hypothalamus in the brain, which acts like a thermostat by detecting temperature changes and starting responses to cool or warm the body.
These responses are usually automatic, so they happen without you having to think about them.
When the body gets too warm, sweat glands release sweat and blood vessels near the skin widen to let heat escape. When the body gets too cold, muscles shiver to make heat and blood vessels near the skin narrow to reduce heat loss. Clothing, hydration, activity level, and the environment all affect how hard the body must work to maintain temperature.
Healthy habits such as drinking water, dressing for the weather, and taking breaks in extreme heat or cold help support temperature regulation.
Key Facts
- Normal core body temperature is about 37°C or 98.6°F, though small changes are normal.
- The hypothalamus senses body temperature and sends signals to organs, muscles, sweat glands, and blood vessels.
- Sweating cools the body because evaporating water carries heat away from the skin.
- Vasodilation means skin blood vessels widen, increasing heat loss to the environment.
- Vasoconstriction means skin blood vessels narrow, reducing heat loss from the body.
- Heat transfer can be summarized as heat lost = heat from skin and sweat evaporation minus heat gained from activity and environment.
Vocabulary
- Homeostasis
- Homeostasis is the process of keeping internal body conditions stable despite changes outside the body.
- Hypothalamus
- The hypothalamus is a part of the brain that helps control body temperature, hunger, thirst, and other automatic functions.
- Sweating
- Sweating is the release of fluid from sweat glands that cools the body as it evaporates from the skin.
- Shivering
- Shivering is rapid muscle movement that produces heat when the body is too cold.
- Vasodilation
- Vasodilation is the widening of blood vessels, which can bring more warm blood near the skin so heat can leave the body.
Common Mistakes to Avoid
- Thinking sweat cools the body just by appearing on the skin is wrong because the main cooling happens when sweat evaporates.
- Assuming body temperature must always be exactly 37°C is wrong because normal temperature can vary slightly with time of day, activity, and measurement method.
- Confusing vasodilation and vasoconstriction is wrong because vasodilation releases more heat while vasoconstriction helps conserve heat.
- Ignoring hydration during hot weather is wrong because sweating uses body water, and dehydration makes cooling less effective.
Practice Questions
- 1 A student has a body temperature of 39°C during intense exercise. How many degrees Celsius above the average 37°C body temperature is this?
- 2 During a workout, a person loses 0.8 L of water through sweat. If they drink 0.5 L of water afterward, what is the remaining fluid loss in liters?
- 3 Explain why a person may have warm, flushed skin in a hot room but pale, cool skin in a cold room. Use blood vessel changes in your answer.