THE EFFECTS OF ALTITUDE ON HUMAN PHYSIOLOGY Essays - Oxygen

THE EFFECTS OF ALTITUDE ON HUMAN PHYSIOLOGY Essays - Oxygen THE EFFECTS OF ALTITUDE ON HUMAN PHYSIOLOGY 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 are two openings. One, the esophagus, leads to the digestive system while the other, the glottis, leads to the lungs. The epiglottis covers the glottis when swallowing so that food does not enter the lungs. When the epiglottis is not covering the opening to the lungs air may pass freely into and out of the trachea. The trachea sometimes called the "windpipe" branches into two bronchi which in turn lead to a lung. Once in the lung the bronchi branch many times into smaller bronchioles which eventually terminate in small sacs called alveoli. It is in the alveoli that the actual transfer of oxygen to the blood takes place. The alveoli are shaped like inflated sacs and exchange gas through a membrane. The passage of oxygen into the blood and carbon dioxide out of the blood is dependent on three major factors: 1) the partial pressure of the gases, 2) the area of the pulmonary surface, and 3) the thickness of the membrane (Gerking, 1969). The membranes in the alveoli provide a large surface area for the free exchange of gases. The typical thickness of the pulmonary membrane is less than the thickness of a red blood cell. The pulmonary surface and the thickness of the alveolar membranes are not directly affected by a change in altitude. The partial pressure of oxygen, however, is directly related to altitude and affects gas transfer in the alveoli. GAS TRANSFER To understand gas transfer it is important to first understand something about the behavior of gases. Each gas in our atmosphere exerts its own pressure and acts independently of the others. Hence the term partial pressure refers to the contribution of each gas to the entire pressure of the atmosphere. The average pressure of the atmosphere at sea level is approximately 760 mmHg. This means that the pressure is great enough to support a column of mercury (Hg) 760 mm high. To figure the partial pressure of oxygen you start with the percentage of oxygen present in the atmosphere which is about 20%. Thus oxygen will constitute 20% of the total atmospheric pressure

How Often Is NO CHANGE the Right Answer on ACT English

How Often Is NO CHANGE the Right Answer on ACT English SAT / ACT Prep Online Guides and Tips On the ACT English section, in the majority of questions, the first answer choice is â€Å"NO CHANGE." The â€Å"NO CHANGE† answer choice indicatesthat the underlined word or phrase is correct. Sometimes, students are hesitant to select â€Å"NO CHANGE† because they think that there should be an error. In this article, I’ll explore the frequency of correct â€Å"NO CHANGE† answers to give you an idea of how often the â€Å"NO CHANGE† answer will be the right one. Furthermore, I’ll let you know how to use this information. For this article, I analyzedthe answers from four published official ACT tests. Basic ACT English Format There are 75 total questions on the ACT English section, each of which has four answer choices. If the correct answers are distributed evenly among the answer choices, â€Å"NO CHANGE† should be right 25% of the time it appears as an option. Let's look at the answers from the four different tests I used. Test-by-Test Breakdown of "NO CHANGE" Frequency Test #1 # of questions w/ "NO CHANGE" option # of correct "NO CHANGE" answers % of "NO CHANGE" answers correct 56 21 37.5% Test #2 # of questions w/ "NO CHANGE" option # of correct "NO CHANGE" answers % of "NO CHANGE" answers correct 64 17 26.6% Test #3 # of questions w/ "NO CHANGE" option # of correct "NO CHANGE" answers % of "NO CHANGE" answers correct 50 17 34 Test #4 # of questions w/ "NO CHANGE" option # of correct "NO CHANGE" answers % of "NO CHANGE" answers correct 59 17 28.8% Frequency of NO CHANGE on All Tests Test # Frequency of "NO CHANGE" correct % of "NO CHANGE" 1 21 37.5 2 17 26.6 3 17 34 4 17 28.8 Analysis: Each test had a percentage of â€Å"NO CHANGE† answers that was higher than expected. The % of NO CHANGE answers ranged from 26.6% to 37.5%. So how can knowing this information benefit you when you take the ACT? How Should You Use This Information? Only use this as a rough guide. The % of â€Å"NO CHANGE† answers varies from test to test. Keep in mind that in ACT English the simplest answer is often the best answer. NO CHANGE may be correct more often than expected because the incorrect answers make unnecessary additions to the underlined phrase. â€Å"NO CHANGE† should always be correct between around 25 and 40 percent of the time. If the percentage of your â€Å"NO CHANGE† answers is not in this range, you have most likely made mistakes and need to review the questions you’re unsure about more closely. Surprisingly, the percentage of No Change is at least 1/4 and often more. So guessing randomly actually is NOT necessarily the best thing to do - when in doubt, try guessing NO CHANGEas it's more likely to be correct! What's Next? As I previously mentioned, in ACT English, the most concise answer is usually the best answer. Learn more about this rule in my article on wordiness on the ACT. If you want a more general guide, read about all the grammar rules covered on the ACT. For those of you primarily studying for the ACT online, I highly recommend checking out this post on the best ACT prep websites. Want to improve your ACT score by 4 points? Check out our best-in-class online ACT prep program. We guarantee your money back if you don't improve your ACT score by 4 points or more. Our program is entirely online, and it customizes what you study to your strengths and weaknesses. If you liked this English lesson, you'll love our program.Along with more detailed lessons, you'll get thousands ofpractice problems organized by individual skills so you learn most effectively. We'll also give you a step-by-step program to follow so you'll never be confused about what to study next. Check out our 5-day free trial:

America in Vladimir Nabokov's Lolita Research Paper

America in Vladimir Nabokov's Lolita - Research Paper Example So much of the consumer society must have been a shock to him, after the deprivations of wartime in Europe, and yet he identified very strongly with many features of his new home. Sweeney quotes Nabokov saying to a journalist in 1966 â€Å"I am as American as April in Arizona† (1994, p. 325) and links this curious alliterative statement with the period when Nabokov and his family lived in Arizona in the Spring of 1953: â€Å"On sunny afternoons that April (and all day long during one rainy week) Nabokov worked at telling one story in particular: Lolita, his most acute observation of America’s beauties and vulgarities, the most cunning, incisive and poetic American novel of this century. (Sweeney, 1994, p. 328). Lolita is set in working class provincial America, and its characters speak the idiom of that milieu. The object of his desire is a world weary twelve year old and Humbert indulges her love of vulgar and transient aspects of American culture: â€Å"Mentally, I found her a disgustingly conventional little girl. Sweet hot jazz, square dancing, gooey fudge sundaes, musicals, movie magazines and so forth.† (Nabokov and Appel, 1991, p. 148)The character of Humbert is portrayed as an immigrant of French origins, and in this character Nabokov plays out part of himself, quoting the narrative style of the realist novelist Flaubert in French with the phrase â€Å"Nous connà »mes† and contrasting this learned reference with the tacky motels that they visit (Nabokov and Appel, 1991, pp. 145-146). He sees the tackiness that is on offer as something faintly ridiculous, but uses it as a means to ingratiate himself with Lolita: â€Å"we had to buy its Indian curios, dolls, copper je welry, cactus candy. The words ‘novelties’ and ‘souvenirs’ simply entranced her by their trochaic lilt† (Nabokov and Appel, p. 148). Humbert merges his own intellectual delight in the language with Lolita’s love of trivia. Through her he learns to both love and hate