Florida natives Marsha and Charlie have arrived in Colorado for a week of hiking in the Rocky Mountains. Within an hour of their first hike (at 10,000 ft), Charlie develops a headache and soon...

  1. Florida natives Marsha and Charlie have arrived in Colorado for a week of hiking in the Rocky Mountains. Within an hour of their first hike (at 10,000 ft), Charlie develops a headache and soon begins to complain about dizziness. Briefly describe how these symptoms are related to changes in blood oxygen and carbon dioxide levels. Is the pH of their blood affected by the change in blood gases?

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Marsha and Charlie have a classic case of altitude sickness.  Their bodies are accustomed to living at sea level (Florida).  While in the Rocky Mountains in Colorado, they are probably living at a minimal altitude of 5,000 feet while hitting 10,000 feet on hikes.  At this altitude, the percentage of oxygen to nitrogen in the air is no different than anywhere else, but the density of the air is less at higher altitudes than at lower altitudes..  So their lungs and circulatory system are receiving less oxygen than they are accustomed to.  As a result, most people start to breathe faster to try to compensate for the lack of oxygen.  So the partial pressure of oxygen and carbon dioxide are decreased in their bloodstreams.  The lowering of carbon dioxide probably very slightly decreases the acidity (raises the pH) of their blood since carbon dioxide dissolved in water produces carbonic acid.  This often results in headache, dizziness, and disorientation, thus giving rise to altitude sickness.  The best way to avoid this is to allow your body to acclimate to the new altitude before beginning any strenuous exercise.

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