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Shows such as 'I Survived' and various news stories showcase human survival instincts as well as how human beings are able to adapt and survive in what seems to be impossible situations. The human body has built-in mechanisms and responses that help humans adapt to various situations to help keep the body going and alive. Most human beings will never be subjected to extreme situations, such as extreme temperatures or weeks without food, but those that are will learn that the body is able to survive. It is important and interesting to learn how the body responds to extreme situations and how it adapts and goes into “survival mode."
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Sense of Taste
Humans, naturally, do not like bitter flavors or foods. Many plants that happen to be toxic have a bitter taste. On the other end of the spectrum, the sugary foods that are sweet and enjoyed by most humans are often used by the body to supply energy (via glucose). Therefore, the sense of taste seems to be on par with what is safe for the body. Sweet things, while not always the healthiest choice can provide energy, are safe and generally taste good. Bitter things could be toxic and humans instinctively do not like the taste. Humans are hard-wired to reject edible things they believe could be harmful based on their sense of taste.
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Fight or Flight
Fight or flight is a response by the human body when it perceives danger or a threat. When this reaction, or response, is occurring, the body releases certain hormones, such as cortisol and adrenalin. This changes a variety of autonomic nervous system functions, such as slowing down digestion, speeding up the heart rate and shunting the flow of blood to the body's major muscle groups. This provides the body with a major burst of strength and energy. Once the danger or threat is gone, the body is designed to go back to functioning normally.
Adrenalin influences the body in a variety of ways and plays a major role in fight or flight. During this response, this hormone is released by the adrenal glands and it then enters the blood stream. The body then responds by opening the lungs' airways, narrowing blood vessels to increase blood flow and increasing blood pressure. All of these actions and responses enable the body to either run or fight when faced with a perceived threat.
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Our Brain in the Wilderness
The brain is touted as the most important tool when it comes to survival. If a person's mind is not focused on survival, their chance of making it out of the wilderness alive, decreases. This, of course, sounds far simpler than it really is. The stress of being in a life or death situation can cloud a person's judgment and make it difficult for them to remember important survival knowledge. Stress is inevitable, but a person can choose how to deal with it. Panicking will certainly make the situation worse. It is important to take a few minutes to breathe and think about the situation. Think about the tools at your disposal, where you are, who you are with, etc. In a nutshell, do an evaluation.
While it is difficult, survival experts regularly preach maintaining a positive mental attitude. This allows people to keep their stress levels lower so that they are able to think more clearly. Less stress also means that the body will take less of a beating because stress also has a negative physical impact. It is important to keep stress down and a positive attitude to keep both the body and the mind healthy, strong and clear when in survival mode.
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The human body is able to thermoregulate to stay alive in extreme temperatures. If humans are in very hot or very cold environments, they can experience either hyperthermia (increased body temperature) or hypothermia (decreased body temperature). Both are dangerous, especially when prolonged. When the body is very hot, processes such as sweating occur to help cool the body, but a person can only sweat so much. When the body is very cold, the body will send blood to the core and start to shiver to stay alive, but this cannot go on forever. In very cold temperatures, frostbite is also a major concern.
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Starvation and Dehydration
There are dozens of myths concerning how long the human body can go without food and water and most are simply not true. Having the facts is critical to survival. Many factors come into play when determining how long a person can go without good. From a medical perspective when thinking about an average healthy adult, most doctors will agree that as long as the person has water, they can live as long as eight weeks without food. Some will not make it the full eight weeks and some will survive longer. Of course, those with medical conditions, the elderly and children would likely not make it close to eight weeks. Another factor is body fat. Those with extra body fat generally survive longer than their leaner counterparts. After a few days without food, a person may notice weakness, chronic diarrhea, bad decision-making, immune deficiency, confusion, irritability and decreased sex drive. When starvation is in the advanced stages, a person may start to experience convulsions, irregular heartbeat, hallucinations and muscle spasms.
Water is far more vital. In an environment with very hot temperatures, a person can start to become dehydrated in as little as an hour. The human body uses water for a variety of functions and it needs to be replaced. It is not known exactly how long a person can go without water and of course, several factors play a role, such as temperature. It is known, however, that a person trying to survive needs a viable fresh water source. Even a day or two without water can be very dangerous for a person trying to survive. Signs of mild dehydration may include no saliva, less urine and urine with a strong color and odor. Moderate dehydration may cause lesser urine, sunken and dry eyes, dry mouth and rapid heartbeat. Severe dehydration may cause irritability and lethargy, no urine and vomiting and diarrhea. Shock is the final stage.
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From an experimental sense, a person is able to go for 264 hours without sleep. This is equal to about 11 days. This was a world record that was set for a science experiment; so of course, this may not be true for all people. The person who set this record was a healthy 17-year-old high school boy. Other research, performed more carefully, has indicated 10 days. However, the longer a person is awake the more they will experience a decrease in concentration, perception and motivation. All of these are vital for survival.
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Living through Extremes
Human survival instincts are more than just hunger pangs and feeling thirsty. The entire body has mechanisms that go into action when it senses danger and uncertainty. By staying calm and paying attention to these mechanisms, humans have gone through the most extreme situations known to man and lived to tell about it.
- Genetic Science Learning Center. (2011). The Fight or Flight Response: http://learn.genetics.utah.edu/content/begin/cells/cellcom/
- Gillin, J.C. (2002). How Long Can Humans Stay Awake?: http://www.scientificamerican.com/article.cfm?id=how-long-can-humans-stay
- Taflinger, R.F. (1996). The Biological Basis of Human Behavior: http://public.wsu.edu/~taflinge/biology.html
- Janiszewski, P. PhD. (2011). The Science of Starvation: How Long Can Humans Survive Without Food or Water?: http://blogs.plos.org/obesitypanacea/2011/05/13/the-science-of-starvation-how-long-can-humans-survive-without-food-or-water/