EFFECT OF ATMOSPHERIC PRESSURE ON THE ENVIROMENT THE BIOSPHERE Variations in atmospheric pressure can present special problems for the respiratory systems of animals because atmospheric pressure affects the exchange of oxygen and carbon dioxide that occurs during animal respiration. Normal atmospheric pressure at sea level is the total pressure that a column of air above the surface of the Earth exerts (760 millimetres of mercury, or 1 atmosphere).
The total pressure is the sum of the pressures that each gas—mainly nitrogen, oxygen, and carbon dioxide—would exert alone (the partial pressure of that gas; see respiration: The gases in the environment). As an animal breathes, oxygen moves from the environment across the respiratory surfaces into the blood; carbon dioxide moves in the reverse direction. This process occurs primarily by passive diffusion; each gas moves from an area of greater to lesser partial pressure, driven by the differential that exists across the respiratory surface.
At higher altitudes, where the atmospheric pressure is lower, the partial pressure of oxygen is also lower. The partial pressure differential of oxygen, therefore, is also lower, and the organism effectively receives less oxygen when it breathes, even though the percentage of oxygen in the air remains constant. This lack of oxygen is why humans carry oxygen when ascending to high altitudes. Humans who live in mountainous regions, however, can become acclimatized to the lowered availability of oxygen, and certain animals such as llamas have adaptations of the blood that allow them to live at high altitudes.
Birds have very efficient lungs, and many apparently have no problems flying to high altitudes, even for extended flight GROWTH Because atmospheric pressure is relatively constant except in the mountains, it probably is of little importance in growth regulation. Increases in pressure in the ocean’s depths may be significant, however, since it is known that increases in hydrostatic pressure interfere with cell division.
Tissues of deep-sea fishes must have become adapted to such pressure effects, which have been little studied thus far. Movements of the terrestrial atmosphere—winds—may affect growth patterns in trees and shrubs, as is evident in the exotic shapes of certain conifers that grow along coastlines exposed to strong prevailing winds. OCCUPATIONAL DISEASE DECOMPRESSION SICKNESS also called BENDS or CAISSON DISEASE can be defined as a physiological effects of the formation of gas bubbles in the body because of rapid transition from a high-pressure environment to one of lower pressure.
Pilots of unpressurized aircraft, underwater divers, and caisson workers are highly susceptible to the sickness because their activities subject them to pressures different from the normal atmospheric pressure experienced on land. At atmospheric pressure the body tissues contain, in solution, small amounts of the gases that are present in the air. When a pilot ascends to a higher altitude, the external pressures upon his body decrease, and these dissolved gases come out of solution.
If the ascent is slow enough, the gases have time to diffuse from the tissues into the bloodstream; the gases then pass to the respiratory tract and are exhaled from the body. Underwater divers breathing compressed air are also faced with the possibility of a form of decompression sickness known as the bends. As they descend into the water, the external pressure increases proportionally to the depth. The compressed air that is breathed is equal in pressure to that of the surrounding water.
The longer a diver stays down and the deeper the dive, the more compressed gas that is absorbed by the body. When the diver ascends, time must be allowed for the additional gases to be expelled slowly or they will form bubbles in the tissues. The major component of air that causes decompression maladies is nitrogen. The oxygen breathed is used up by the cells of the body and the waste product carbon dioxide is continuously exhaled. Nitrogen, on the other hand, merely accumulates in the body until the tissue becomes saturated at the ambient pressure.
When the pressure decreases, the excess nitrogen is released. Nitrogen is much more soluble in fatty tissue than in other types; therefore, tissues with a high fat content (lipids) tend to absorb more nitrogen than do other tissues. The nervous system is composed of about 60 percent lipids. Bubbles forming in the brain, spinal cord, or peripheral nerves can cause paralysis and convulsions (divers’ palsy), difficulties with muscle coordination and sensory abnormalities (divers’ staggers), numbness, nausea, speech defects, and personality changes.
When bubbles accumulate in the joints, pain is usually severe and mobility is restricted. The term bends is derived from this affliction, as the affected person commonly is unable to straighten joints. Small nitrogen bubbles trapped under the skin may cause a red rash and an itching sensation known as divers’ itches. Usually these symptoms pass in 10 to 20 minutes. Excessive coughing and difficulty in breathing, known as the chokes, indicate nitrogen bubbles in the respiratory system.
Other symptoms include chest pain, a burning sensation while breathing, and severe shock. Relief from decompression sickness usually can be achieved only by recompression in a hyperbaric chamber followed by gradual decompression, but this process is not always able to reverse damage to tissues. Chapter 5 conclusion The study of atmospheric pressure is very important in meterolgy because of its effect on the climate.
It helps in the determination of regions of relatively very low pressure(cyclones) and regions of relatively high pressure(anticyclones) that occur over most of earths surface in a variety of sizes ranging from the very large semi- permanent examples described above to smaller,highly mobile systems. Atmospheric pressure and wind are both significant controlling factors of Earth’s weather and climate. Though these two physical variables may at first glance appear to be quite different, they are in fact closely related.
Wind exists because of horizontal and vertical differences (gradients) in pressure, yielding a correspondence that often makes it possible to use the pressure distribution as an alternative representation of atmospheric motions. Partly because of this,the smallest variations in pressure that do exist largely determine the wind and storm patterns of the Earth. It has also been observed that near the Earth’s surface the pressure decreases with height at a rate of about 3. 5 millibars for every 30 metres (100 feet). However, over cold air the decrease in pressure can be much steeper because its density is greater than warmer air.
The pressure at 270,000 metres (10? 6 mb) is comparable to that in the best man-made vacuum ever attained,so it is possible that at heights above 1,500 to 3,000 metres (5,000 to 10,000 feet), the pressure is low enough to produce mountain sickness and severe physiological problems unless careful acclimatization is undertaken. Finally some occupational diseases like decompression sickness,bends associated with underwater divers,caisson workers and pilots of unpressurized aircraft, occur due to the rapid transition from a high pressure environment to a lower one common with these occupations.