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

Write About What You Know

Write About What You Know Write About What You Know Write About What You Know By Michael For thirty years, the mid-term exam for Dr. McAnellys Biblical Literature class was always the same essay question: Describe the wandering journeys of the Apostle Paul. So a college football fullback and his roommate decided they wouldnt study anything else, thereby leaving them more time for other attractive pursuits. Imagine their surprise when the question instead was, Critique the major themes of Jesus Sermon on the Mount. Now, imagine the fullbacks surprise when his roommate nevertheless began to write furiously for the next hour. The fullback stared at his blank test paper for a long time before giving up and leaving the room, but his curiosity was so strong that he peeked at his roommates essay as he walked past. The first sentence read, Who am I to critique the words of the Lord Jesus? Let me rather describe the wandering journeys of the Apostle Paul. Seasoned authors advise, Write about what you know. In fact, you have to write about what you know. Try to write about what you dont know, about which you havent got a clue, and youll be staring at a blank piece of paper for a long time. Its one of the surest ways to contract writers block. If you succeed in actually getting words onto the page, your readers will be staring at it for a long time, trying to figure out what you just said, if not why you wrote it in the first place. Why would anybody write about what they dont know? Why would people do something like that? Because someone important told them to. Essay tests in school are a good example. Your instructor asks you to write about one of the (several) chapters in the textbook that you never got around to studying. Your job, should you choose to accept it, is to employ your literary skills to make your instructor believe that you read and understood the chapter. Changing the question rarely works. Because what they dont know seems more interesting than what they do know. Young writers frequently make that mistake. When you move into the cloud of unknowing to write your piece, youre increasing your competition. In the mid-60s, without having any personal experience with them, lots of American teenagers were probably writing about monsters and spaceships, though these markets were already fully stocked with experienced grown-up writers. None of them wrote about being a real American teenager except S.E. Hinton. So her book The Outsiders got published and their books didnt. Because they value style over communication. Poets sometimes make this mistake. They write about the universal life force, instead of about a tree. Down-to-earth, brass-tacks writing doesnt seem stylish enough. But uninformed writing is less interesting than informed writing. The details which make writing vivid and readable are missing, like a price tag in a store, or somehow off, like a carton of old milk. Writing about what you know is a cure for writers block. Thats one reason why journaling or blogging is so popular among writers. Something must have happened to you today, unless you were dead. Write about it. It didnt happen to anyone else, unless youre a clone. Nobody has the same brain or biography as you, so nobody has the same perspective as you. If they do, I suggest you get your own perspective. You need your own. Dont try to share with your neighbor. Thats cheating. Want to improve your English in five minutes a day? Get a subscription and start receiving our writing tips and exercises daily! Keep learning! Browse the Writing Basics category, check our popular posts, or choose a related post below:When to Capitalize Animal and Plant NamesComma Before ButAppropriate vs. Apropos vs. Apt