47 Going Up!-Mid

Going Up! FOCUS Question How does high altitude affect the human body?

Sea-Level Survivors Most people on Earth live at or near sea. level—the level. of the surface of the sea The human body is able to handle the conditions at sea level. The pressure inside our body is balanced with the outside air pressure pushing in on us. Our lungs and red blood cells work well due to the plentiful oxygen in the air near sea level. Things are different up in the atmosphere. If you were suddenly placed atop Mount Everest—the highest place on Earth—you would feel a drop in air pressure. With less air pushing in on you, your face and hands might swell. Oxygen molecules at that altitude are farther apart, so breathing would become more difficult.

Air Pressure What is air pressure, and how does it change with altitude? Earth's atmosphere is made up of billions upon billions of air molecules, including the oxygen molecules that we breathe. All these molecules stack up and press down on Earth's surface. Air pressure is a measurement of the weight of all those molecules. Moving up from sea level, fewer and fewer air molecules are in the column of air above you. Therefore, the air pressure goes down. With less pressure, air molecules spread out and move farther apart. The greater the altitude the lower the air pressure.

High-Altitude Side Effects For most people, exposure to high altitude causes problems. Their feet and hands swell. People breathe faster and more deeply to get more oxygen into their lungs. Because they are not getting enough oxygen, people may feel tired. It may also be harder to fall asleep and hard to wake up. Since there is less moisture in the air at high altitude, it is easy to become dehydrated. At high altitude, people exhale, sweat, and urinate more So their bodies lose even more moisture. Finally, people may suffer from altitude sickness. This means they may vomit, get headaches, or feel as though they have the flu. So how do people safely climb to high altitudes? Math Moment Using the diagram answer this question: At what altitude is the air pressure about half the air pressure at sea level?

Climbing Into Thin Air Climbing mountains can be safe and fun! It's important to bring lots of water while hiking in the mountains. People lose twice the moisture at 1,828 meters (6,000 ft.) as they do at sea level. Many climbers also carry bottled oxygen with them when hiking at very high altitude. They spend just a short time at the top of a tall mountain to avoid getting sick. Gradually adjusting to altitude can also help climbers. Each time a person climbs to a higher altitude, he or she rests for at least a day. The body has time to adjust to the new conditions. This process is called acclimatization. Given time, the body can even make more red blood cells than usual to help carry oxygen.

High-Altitude Humans Some people have an easier time at high altitude. Their bodies have special adaptations to the lower air pressure. People in Tibet have been living in high mountains longer than any group of people on Earth. They have larger lungs than people at sea level. Larger lungs help them take in more oxygen. Some people in East Africa also live at high altitude. Their bodies make more red blood cells to carry more oxygen throughout their body. With larger lungs, they can also take in more air with each breath than people who live at sea level. Do You Know? In part because they live at high altitude, some East African people are amazing long- distance runners Lelisa Desisa is from Ethiopia. He won the Boston Marathon in 2015.