The Effects Of Altitude On Human Physiology
Uploaded by Admin on Jan 22, 1999
Changes in altitude have a profound effect on the human body. The body attempts to maintain a state of homeostasis or balance to ensure the optimal operating environment for its complex chemical systems. Any change from this homeostasis is a change away from the optimal operating environment. The body attempts to correct this imbalance. One such imbalance is the effect of increasing altitude on the body's ability to provide adequate oxygen to be utilized in cellular respiration. With an increase in elevation, a typical occurrence when climbing mountains, the body is forced to respond in various ways to the changes in external environment. Foremost of these changes is the diminished ability to obtain oxygen from the atmosphere. If the adaptive responses to this stressor are inadequate the performance of body systems may decline dramatically. If prolonged the results can be serious or even fatal. In looking at the effect of altitude on body functioning we first must understand what occurs in the external environment at higher elevations and then observe the important changes that occur in the internal environment of the body in response.
HIGH ALTITUDE
In discussing altitude change and its effect on the body mountaineers generally define altitude according to the scale of high (8,000 - 12,000 feet), very high (12,000 - 18,000 feet), and extremely high (18,000+ feet), (Hubble, 1995). A common misperception of the change in external environment with increased altitude is that there is decreased oxygen. This is not correct as the concentration of oxygen at sea level is about 21% and stays relatively unchanged until over 50,000 feet (Johnson, 1988).
What is really happening is that the atmospheric pressure is decreasing and subsequently the amount of oxygen available in a single breath of air is significantly less. At sea level the barometric pressure averages 760 mmHg while at 12,000 feet it is only 483 mmHg. This decrease in total atmospheric pressure means that there are 40% fewer oxygen molecules per breath at this altitude compared to sea level (Princeton, 1995).
HUMAN RESPIRATORY SYSTEM
The human respiratory system is responsible for bringing oxygen into the body and transferring it to the cells where it can be utilized for cellular activities. It also removes carbon dioxide from the body. The respiratory system draws air initially either through the mouth or nasal passages. Both of these passages join behind the hard palate to form the pharynx. At the base of the pharynx...