The word "exert" in line 15 is closest in meaning toĢ4. The words "exposed to" in line 6 are closest in meaning toĢ3. (d) The symptoms of nitrogen bubbles in the bloodstreamĢ2. (b) The effects of pressure on gases in the human body
To avoid this event, a diver must ascend slowly, never at a rate exceeding the rise of the exhaled air bubbles, and must exhale during ascent.Ģ1. This change in volume may cause the lungs to distend and even rupture. (25) pressure at the surface is only half of what it was at 10 meters. During ascent from a depth of 10 meters, the volume of air in the lungs will double because the air
They can cause severe pains, particularly around the joints.Īnother complication may result if the breath is held during ascent. (20) If the return to the surface is too rapid, nitrogen in the tissues and blood cannot diffuse out rapidly enough and nitrogen bubbles are formed. The reverse occurs when the diver surfaces the nitrogen pressure in the lungs falls and the nitrogen diffuses from the tissues into the blood, and from the blood into the lungs. Nitrogen then diffuses from the lungs to the blood, and from the blood to body tissues. As a scuba diver descends, the pressure of nitrogen in the lungs increases. (15) nitrogen, because under these pressures helium does not exert a similar narcotic effect. Deep dives are less dangerous if helium is substituted for Nitrogen narcosis apparently results from a direct effect on the brain of the large amounts of nitrogen dissolved in the blood. At a depth of 5 atmospheres, nitrogen causes symptoms resembling alcohol intoxication, known as nitrogen narcosis. (10) composes 80 percent of the air we breathe, usually causes a balmy feeling of Therefore all of the gases in the air breathed by a scuba diver at 40 meters are present at five times their usual pressure. The pressure of the gases being breathed must equal the external pressure applied to the body otherwise breathing is very difficult. (5) by 1 atmosphere for every 10 meters of depth in seawater, so that at 30 meters in seawater a diver is exposed to a pressure of about 4 atmospheres. The pressure exerted on the human body increases For example, gas pressures increase rapidly during a dive made with scuba gear because the breathing equipment allows divers to stay Under certain circumstances, the human body must cope with gases at greater-than-normal atmospheric pressure.
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