Survival Needs Of The Body

Learning Objectives

By the end of this section, you will be able to:

Discuss the role of oxygen and nutrients in maintaining human survival
Explain why extreme heat and extreme common cold threaten human being survival
Explain how the pressure level exerted past gases and fluids influences human survival

Humans have been acclimating to life on World for at least the past 200,000 years. Earth and its temper have provided usa with air to breathe, water to potable, and food to eat, but these are not the but requirements for survival. Although you may rarely recall about information technology, you lot also cannot live outside of a sure range of temperature and pressure that the surface of our planet and its temper provides. The side by side sections explore these four requirements of life.

Oxygen

Atmospheric air is only about twenty percent oxygen, but that oxygen is a key component of the chemical reactions that keep the body alive, including the reactions that produce ATP. Brain cells are especially sensitive to lack of oxygen because of their requirement for a loftier-and-steady production of ATP. Brain impairment is likely within five minutes without oxygen, and death is likely inside ten minutes.

Nutrients

A nutrient is a substance in foods and beverages that is essential to homo survival. The iii bones classes of nutrients are water, the energy-yielding and trunk-building nutrients, and the micronutrients (vitamins and minerals).

The virtually critical nutrient is water. Depending on the ecology temperature and our land of wellness, we may be able to survive for only a few days without h2o. The trunk's functional chemicals are dissolved and transported in water, and the chemical reactions of life take identify in water. Moreover, water is the largest component of cells, claret, and the fluid between cells, and water makes upward nearly 70 pct of an adult's body mass. Water also helps regulate our internal temperature and cushions, protects, and lubricates joints and many other body structures.

The energy-yielding nutrients are primarily carbohydrates and lipids, while proteins mainly supply the amino acids that are the building blocks of the torso itself. You ingest these in plant and animal foods and beverages, and the digestive organisation breaks them down into molecules small plenty to be absorbed. The breakdown products of carbohydrates and lipids can and then be used in the metabolic processes that convert them to ATP. Although you might feel equally if y'all are starving afterwards missing a unmarried meal, yous can survive without consuming the energy-yielding nutrients for at least several weeks.

Water and the energy-yielding nutrients are as well referred to as macronutrients because the trunk needs them in large amounts. In contrast, micronutrients are vitamins and minerals. These elements and compounds participate in many essential chemical reactions and processes, such as nerve impulses, and some, such every bit calcium, also contribute to the body's structure. Your body can store some of the micronutrients in its tissues, and draw on those reserves if you fail to consume them in your diet for a few days or weeks. Some others micronutrients, such equally vitamin C and about of the B vitamins, are water-soluble and cannot be stored, and then you demand to consume them every day or two.

Narrow Range of Temperature

Yous have probably seen news stories about athletes who died of heat stroke, or hikers who died of exposure to cold. Such deaths occur because the chemic reactions upon which the body depends can but take place within a narrow range of body temperature, from just below to just above 37°C (98.6°F). When body temperature rises well above or drops well below normal, certain proteins (enzymes) that facilitate chemical reactions lose their normal structure and their ability to function and the chemical reactions of metabolism cannot keep.

That said, the body can respond effectively to short-term exposure to heat (Figure 1.viii) or cold. One of the body's responses to heat is, of course, sweating. As sweat evaporates from skin, it removes some thermal energy from the body, cooling it. Adequate water (from the extracellular fluid in the body) is necessary to produce sweat, so adequate fluid intake is essential to balance that loss during the sweat response. Not surprisingly, the sweat response is much less effective in a humid environment because the air is already saturated with water. Thus, the sweat on the skin's surface is not able to evaporate, and internal body temperature tin get dangerously high.

This photo shows two white-clad men riding camels through a sparse desert. Two canvas tents are visible in the background.

Figure 1.8 Extreme Heat Humans acclimate to some degree to repeated exposure to high temperatures. (credit: McKay Savage/flickr)

The body can also respond finer to short-term exposure to common cold. One response to cold is shivering, which is random muscle move that generates oestrus. Another response is increased breakdown of stored energy to generate oestrus. When that energy reserve is depleted, however, and the core temperature begins to drop significantly, reddish blood cells will lose their ability to give up oxygen, denying the brain of this disquisitional component of ATP production. This lack of oxygen can cause confusion, lethargy, and somewhen loss of consciousness and death. The torso responds to cold past reducing blood apportionment to the extremities, the easily and anxiety, in social club to foreclose claret from cooling in that location and then that the torso's core can stay warm. Even when core body temperature remains stable, notwithstanding, tissues exposed to severe cold, peculiarly the fingers and toes, can develop frostbite when claret flow to the extremities has been much reduced. This grade of tissue damage tin can exist permanent and lead to gangrene, requiring amputation of the afflicted region.

Everyday Connection

Controlled Hypothermia

Equally you have learned, the body continuously engages in coordinated physiological processes to maintain a stable temperature. In some cases, however, overriding this system tin can exist useful, or even life-saving. Hypothermia is the clinical term for an abnormally depression body temperature (hypo- = "below" or "under"). Controlled hypothermia is clinically induced hypothermia performed in order to reduce the metabolic rate of an organ or of a person's entire body.

Controlled hypothermia frequently is used, for example, during open-heart surgery because it decreases the metabolic needs of the encephalon, center, and other organs, reducing the risk of damage to them. When controlled hypothermia is used clinically, the patient is given medication to prevent shivering. The body is then cooled to 25–32°C (79–89°F). The heart is stopped and an external centre-lung pump maintains circulation to the patient's trunk. The center is cooled farther and is maintained at a temperature below 15°C (60°F) for the duration of the surgery. This very common cold temperature helps the heart muscle to tolerate its lack of claret supply during the surgery.

Some emergency department physicians use controlled hypothermia to reduce damage to the heart in patients who have suffered a cardiac arrest. In the emergency department, the physician induces coma and lowers the patient'due south torso temperature to approximately 91 degrees. This condition, which is maintained for 24 hours, slows the patient's metabolic rate. Because the patient's organs crave less blood to function, the middle's workload is reduced.

Narrow Range of Atmospheric Pressure

Pressure is a force exerted by a substance that is in contact with another substance. Atmospheric pressure level is pressure exerted by the mixture of gases (primarily nitrogen and oxygen) in the Earth's temper. Although you may not perceive information technology, atmospheric pressure level is constantly pressing down on your body. This pressure keeps gases within your body, such as the gaseous nitrogen in trunk fluids, dissolved. If you lot were suddenly ejected from a space ship higher up Globe'southward atmosphere, you would go from a situation of normal pressure to i of very depression force per unit area. The pressure level of the nitrogen gas in your blood would be much higher than the pressure of nitrogen in the space surrounding your body. As a result, the nitrogen gas in your blood would expand, forming bubbles that could block blood vessels and even cause cells to interruption apart.

Atmospheric pressure level does more than just go along claret gases dissolved. Your ability to exhale—that is, to take in oxygen and release carbon dioxide—also depends upon a precise atmospheric pressure. Altitude sickness occurs in role considering the atmosphere at high altitudes exerts less pressure, reducing the exchange of these gases, and causing shortness of breath, confusion, headache, lethargy, and nausea. Mountain climbers carry oxygen to reduce the furnishings of both low oxygen levels and low barometric pressure level at higher altitudes (Figure ane.9).

This photo shows Mount Everest as seen from a distance. It is a large, pyramid-shaped, craggy peak with many smaller snow-covered peaks in the foreground. The peak of Mount Everest is partially occluded by clouds.

Figure 1.9 Harsh Conditions Climbers on Mountain Everest must accommodate extreme cold, low oxygen levels, and depression barometric pressure in an surroundings hostile to human being life. (credit: Melanie Ko/flickr)

Homeostatic Imbalances

Decompression Sickness

Decompression sickness (DCS) is a condition in which gases dissolved in the blood or in other body tissues are no longer dissolved following a reduction in pressure on the torso. This status affects underwater divers who surface from a deep dive too chop-chop, and it can affect pilots flying at high altitudes in planes with unpressurized cabins. Divers often call this status "the bends," a reference to articulation pain that is a symptom of DCS.

In all cases, DCS is brought about past a reduction in barometric pressure. At high altitude, barometric force per unit area is much less than on Earth'south surface because pressure is produced by the weight of the column of air to a higher place the body pressing downward on the body. The very keen pressures on divers in deep water are likewise from the weight of a cavalcade of water pressing down on the trunk. For divers, DCS occurs at normal barometric force per unit area (at sea level), simply it is brought on past the relatively rapid decrease of pressure every bit divers rising from the high pressure conditions of deep water to the now low, past comparison, pressure at bounding main level. Not surprisingly, diving in deep mountain lakes, where barometric pressure at the surface of the lake is less than that at body of water level is more likely to result in DCS than diving in water at body of water level.

In DCS, gases dissolved in the claret (primarily nitrogen) come up quickly out of solution, forming bubbles in the blood and in other body tissues. This occurs because when pressure level of a gas over a liquid is decreased, the amount of gas that tin remain dissolved in the liquid also is decreased. Information technology is air pressure that keeps your normal blood gases dissolved in the blood. When pressure is reduced, less gas remains dissolved. Yous have seen this in result when y'all open up a carbonated drink. Removing the seal of the bottle reduces the force per unit area of the gas over the liquid. This in plough causes bubbles as dissolved gases (in this case, carbon dioxide) come out of solution in the liquid.

The most common symptoms of DCS are pain in the joints, with headache and disturbances of vision occurring in 10 percentage to fifteen percent of cases. Left untreated, very severe DCS can result in decease. Firsthand treatment is with pure oxygen. The affected person is then moved into a hyperbaric chamber. A hyperbaric chamber is a reinforced, closed chamber that is pressurized to greater than atmospheric force per unit area. It treats DCS past repressurizing the body so that pressure can then exist removed much more gradually. Because the hyperbaric chamber introduces oxygen to the body at high pressure, it increases the concentration of oxygen in the claret. This has the effect of replacing some of the nitrogen in the blood with oxygen, which is easier to tolerate out of solution.

The dynamic pressure of body fluids is also important to homo survival. For instance, blood force per unit area, which is the pressure exerted by claret every bit it flows within blood vessels, must be great plenty to enable claret to achieve all body tissues, and yet low plenty to ensure that the delicate blood vessels tin can withstand the friction and forcefulness of the pulsating period of pressurized claret.