Humans cannot survive for more than a few minutes without oxygen, for more than several days without water, and for more than several weeks without carbohydrates, lipids, proteins, vitamins, and minerals. Although the body can respond to high temperatures by sweating and to low temperatures by shivering and increased fuel consumption, long-term exposure to extreme heat and cold is not compatible with survival. The body requires a precise atmospheric pressure to maintain its gases in solution and to facilitate respiration—the intake of oxygen and the release of carbon dioxide. Humans also require blood pressure high enough to ensure that blood reaches all body tissues but low enough to avoid damage to blood vessels.
nutrient
chemical obtained from foods and beverages that is critical to human survival
pressure
force exerted by a substance in contact with another substance
1. Humans have the most urgent need for a continuous supply of ________.
A) food
B) nitrogen
C) oxygen
D) water
C
2. Which of the following statements about nutrients is true?
A) All classes of nutrients are essential to human survival.
B) Because the body cannot store any micronutrients, they need to be consumed nearly every day.
C) Carbohydrates, lipids, and proteins are micronutrients.
D) Macronutrients are vitamins and minerals.
A
3. C.J. is stuck in her car during a bitterly cold blizzard. Her body responds to the cold by ________.
A) increasing the blood to her hands and feet
B) becoming lethargic to conserve heat
C) breaking down stored energy
D) significantly increasing blood oxygen levels
C
1. When you open a bottle of sparkling water, the carbon dioxide gas in the bottle form bubbles. If the bottle is left open, the water will eventually “go flat.” Explain these phenomena in terms of atmospheric pressure.
In a sealed bottle of sparkling water, carbon dioxide gas is kept dissolved in the water under a very high pressure. When you open the bottle, the pressure of the gas above the liquid changes from artificially high to normal atmospheric pressure. The dissolved carbon dioxide gas expands, and rises in bubbles to the surface. When a bottle of sparkling water is left open, it eventually goes flat because its gases continue to move out of solution until the pressure in the water is approximately equal to atmospheric pressure.
2. On his midsummer trek through the desert, Josh ran out of water. Why is this particularly dangerous?
The primary way that the body responds to high environmental heat is by sweating; however, sweating requires water, which comes from body fluids, including blood plasma. If Josh becomes dehydrated, he will be unable to sweat adequately to cool his body, and he will be at risk for heat stroke as his blood pressure drops too much from the loss of water from the blood plasma.