What is Dehydration? - Definition, Causes & Symptoms

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  • 0:01 Water & the Human Body
  • 1:16 How Does Dehydration Occur?
  • 3:27 What Are Some of the…
  • 5:14 Lesson Summary
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Lesson Transcript
Instructor: John Williams
Dehydration is a condition where the water levels in the body are too low. This can result in numerous minor and major effects within the body and can be deadly. This article addresses dehydration, its causes, its symptoms and effects.

Water & the Human Body

Here is one of the most basic facts of human biology: water is essential for life. The human body is approximately 70% water, and water is necessary for many of the human bodily processes. It makes up a large volume of the cytosol in your cells, which is the fluid that supports the organelles. It is a large component of our bodily fluids and tissues, including blood, sweat, and tears. It is also a vital component in the digestion of food for nutrients and is used to break down food in a process known as catabolism. These processes, and many others, tell us that without water, it is impossible to survive.

Therefore, human bodies are very sensitive to changes in the amount of water that is in the system. Increases in water, known as overhydration, can be deadly and can lead to a condition known as water intoxication. Conversely, decreases in water may lead to dehydration, which is a condition that can also be deadly. This lesson will discuss dehydration and its effects within the human body.

How Does Dehydration Occur?

Homeostasis is when the body maintains a stable internal environment. One aspect of homeostasis is proper levels of water within the body. Human bodies are designed to recognize when water levels are too low, and will stimulate a response in order to bring in more. For example, when you get thirsty, your body is signaling a need for water so that we will drink more and raise our water levels. Additionally, if we are low on water, our bodies will reduce the amount of sweat and urine we produce in order to slow down fluid loss. Most of these responses are efficient under normal circumstances and can bring the water levels back to homeostasis.

Dehydration occurs when any of these responses are affected, either physically or chemically. For example, say you are working out heavily. Of course, you will begin to sweat in order to cool your body temperature. However, if you do not replenish your fluids periodically, you may begin to stop sweating. That is a signal that you are becoming dehydrated. People who ignore thirst during exercise, or who do not drink fluids properly while working out, often become dehydrated because of a physical lack of replacement fluids.

Another example of dehydration can occur when the temperature becomes too high. If you live in Florida, for example, you know that the temperature is often well above our normal body temperature, and will often cause sweating. Individuals who are in places where the temperature is high must remember to replace fluids, or they will become dehydrated.

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