IS IT HOT IN HERE, OR WHAT?!?!
One of the most possible hostile environments for humans is the excessive heat environment, also known as extreme heat environments. Extreme heat environments put our body's ability to cope and adapt to the test. We aim to distinct between acute (short term) physiological responses to heat vs chronic (long term) physiological responses to heat.
Any time that the environment is hotter than the core temperature of the body, an inward heat absorbing gradient (see separate post) is created. An inward heat absorbing gradient causes heat to travel form the environment into the body (inwards), thus causing body core temperature to increase. In other words, the body is heating up, getting hotter.
Advertisement
As is the case with gradients, the greater the difference in value between the two values that represent the gradients components and their extent, the stronger the gradient is, the more movement it will create, and the faster the movement will be. Accordingly, excessive heat environments will increase body core temperature faster than non-excessive heat environments. One of five processes used to get rid of body heat and thus cool down the body, is sweating.
Sweating demands the getting heat to the skin's surface via the solution known as sweat. Sweat is basically water with NaCl (sodium chloride; table salt), where the water is most likely taken out from blood tissue. The more we need to sweat as a solution to cooling down the body, the more water is taken out from the blood. As water is removed more and more from blood tissue, blood itself becomes more viscous.
Viscous blood tends to move and flow less, as it is harder to push and circulate, resulting in blood moving slower. Viscous blood increases its resistance to movement. As blood becomes more and more viscous, the heart struggles to pump it out of its ventricles. This immediately means a decrease in stroke volume (mL), which requires heart rate (bpm) to increase as compensation maintaining cardiac output (L/min) the same. Any decrease in cardiac output will influence function; the more cardiac output is lower than required for normal function, the worse the body's situation becomes, and the faster.
Without external means, especially means of hydration and/or stopping any physical activity/exercise/sports, heart rate will continue to rise until maximal heart rate is reached. Once maximal heart rate is achieved, it can no longer increase, and can no longer compensate for the decreasing stroke volume. This is a negative turning point where cardiac output must decrease below needed levels. The more and more viscous blood becomes, the more and more stroke volume decreases, the more and more cardiac output decreases.
As cardiac output decreases, less and less oxygen is delivered to the cells. The less oxygen delivered to the cells, the more the cells (especially skeletal muscles) must relay on anaerobic glycolysis, causing a vast and sharp increase in acid production and the acidity of the environment. Immediately, three tissue types central to function are influenced by the increasing acidity. these include out nerves, red blood cells (RBCs), and skeletal muscles (other tissue may experience reduce function as well).
Dysfunctional nerve cause sensory loops to be dysfunctional, negatively influencing the brain's ability to supervise and regulate what is going on. In addition, cognition, coordination, balance, stability, logic, and being able to "tap" into knowledge and act upon it, are severely reduced as cardiac output continues to decrease, and acidity continues to increase. This may pose a grave danger to our ability to take actions to save ourself as confusion and disorientation occur and worsen.
Red blood cells that make up about 44-45% of the volume of blood, carry within them a protein known as hemoglobin. Hemoglobin in turn is the prime carrier of oxygen to the needing cells, and carbon di oxide remover (disposer) from the cells. As acidity increases, the function of red blood cells is impaired, oxygen supply is reduced (hypoxia) and carbon di oxide removal is also reduced, causing an even greater increase in acidity.
We utilize blood flow to our skin as a means to get rid of heat. As cardiac output is decreasing more and more, less blood is pumped on a minute by minute basis, reducing the capacity to get rid of heat from the body (i.e. reducing our capacity to cool body core temperature). The less heat is disposed of, the more core temperature increases, the more we sweat, the more water continues to be removed from blood. This results in an endless and lethal circle of death.
If not bad and dangerous enough for you, the increase in anaerobic glycolysis causes a rapid consumption of carbs. Since nerves and red blood cells are "avid" consumers of carbs for energy production, their function is negatively influenced even more. To add danger to a dangerous situation, and in order to supply necessary carbs for neural function, proteins are consumed in a growing rate, increasing the extent of poisonous gases released into the cells, and causing rapid breakdown of skeletal muscle mass. At pathological extents, this is known as Rhabdomyolysis that can be deadly if not stopped/treated. Under extreme circumstances, Rhabdomyolysis can kill within 4 hours. If not lethal, Rhabdomyolysis can cause severe liver dysfunction, including the need for dialysis.
Advertisement
Notice that almost every paragraphs increases out knowledge of how excessive heat environments create a physiological "death trap" that occurs ever faster and deadlier as time passes by and cardiac output is not restored.
Behavioral measures can be taken to reduce the risk of existence and/or physical activity in a hostile hot environment. For example, taking a 15 minute break for every 35-45 minutes of moderate intensity effort, a 20 minutes break for every 35-45 minutes of high intensity intensity (rigorous) effort. The least the break must be is 15 minutes since it takes the body at least 7 minutes to start effectively reducing body core temperature, and 8 more minutes to actually get rid of the heat accumulated. If in a group, the 15 minutes must begin from the moment that the last person arrives to the rest of the group.
The only way to truly stop or eliminate this death trap from occurring at all or getting worse, is to restore blood volume (especially blood water volume). Thus, proper hydration means, breathable clothing, reduced extent of body exposure to the environment (mainly skin), a wide hat, isolating shoes, as well as anything else that reduces heat absorption. In the absence of any of this means, airborne transportation may be required to save the person's life.
コメント