Final answer:
Dehydration is the condition where fluid loss exceeds intake, causing a reduction in total body water. Symptoms of severe dehydration can include dizziness and fainting and could lead to a medical emergency. Infants, athletes, and individuals with certain illnesses are at higher risk of rapid dehydration.
Step-by-step explanation:
The condition when fluid output exceeds fluid intake and results in a decrease in total body water is known as dehydration. This occurs because the body is experiencing a negative water balance due to higher fluid loss relative to intake. Potential causes of dehydration include vomiting, diarrhoea, excessive sweating, and illnesses that increase water loss or hinder water intake. Symptoms of severe dehydration can include dizziness, low blood pressure, and fainting, indicating a medical emergency requiring immediate attention.
Infants and endurance athletes are particularly at risk for rapid onset of dehydration. In infants, due to their low body mass and high metabolic rate, dehydration can develop quickly and be life-threatening. For athletes, especially in long races or activities, the combination of high physical exertion and sweat loss can result in critical dehydration if not properly managed with adequate water intake.
The kidneys also play a vital role in fluid balance. In conditions like oliguria, the reduced excretion of urine below 600 ml/day is observed and can be indicative of dehydration or other underlying health issues. Additionally, biological systems interact with the environment, exchanging water and nutrients; when this exchange is disrupted, the body can experience an accumulation of toxic waste and water, leading to serious consequences.