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   Place your response to this activity below. You will be marked according to your explanation of the body’s response to the two given situations. You must include references to vasoconstriction, vasodilation, countercurrent heat exchange, and peripheral heat loss.

Thermoregulation is the term used when biological systems attempt to maintain temperature. After watching the previous animations and reading the textbook, prepare a summary table. Outline the body’s thermoregulatory response to

•   an increase in internal temperature due to exertion
•   a colder external temperature than body temperature

Explain how peripheral heat loss, selective vasoconstriction, vasodilation, and countercurrent heat exchange are involved in each circumstance.

    Increased temperature (body)  due to exertion   T (body) > T (environment)
Peripheral heat loss      
Vasoconstriction/vasodilation      
Countercurrent exchange

The hypothalamus, an area of the brain that functions as the body's thermostat, plays an important role during exercise. Normally, your body stays at a core temperature between 97.7 and 99.5 degrees Fahrenheit, but during exercise, your temperature can go even higher --- up to 104 degrees if you don't cool off properly. Your hypothalamus helps with thermoregulation, or adapting to changing temperatures.

How Does Exercise Make You Hot?

Mitochondria, miniscule components of your muscle cells, help your body turn nutrients and oxygen into energy. Every time you contract your muscles during a workout, you produce energy. Being an inefficient machine, your body loses about 75 percent of that energy in the form of heat. Heat from the muscles then moves to the blood, which circulates throughout your body, making your temperature rise.

How Does the Body Cool Down?

As the temperature in your blood rises, it triggers the hypothalamus to try to cool your body. The hypothalamus, in turn, sends signals to increase blood flow to the skin, where the heat can activate your sweat glands. As the sweat evaporates, your body cools.

Why is Hydration Important?

Water constitutes a large part of blood volume. When you don't drink enough water to replace the amount lost through sweat, your blood volume decreases, leading to symptoms of dehydration, like dry mouth and lightheadedness. When exercising, most people lose 1 to 2 liters of water per hour.

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