. Which statement best explains why the concentration of substances must be regulated in the human body?
To allow for body growth
To keep the immune system active
To ensure proper chemical reactions occur without disruption
To support external temperature changes
The Correct Answer is C
A. To allow for body growth: Growth is a complex process involving hormonal signaling and nutrient assimilation. While homeostasis supports growth, the immediate requirement for concentration regulation is the preservation of current cellular function. Regulation prevents acute metabolic failure rather than just promoting long-term growth.
B. To keep the immune system active: Immune function requires a stable environment, but the regulation of electrolytes and pH is broader than immunological health. Every cell in the body, including neurons and myocytes, depends on precise chemical concentrations. Regulation is a universal requirement for all physiological systems.
C. To ensure proper chemical reactions occur without disruption: Precise concentrations of hydrogen ions, enzymes, and substrates are necessary for the kinetics of life-sustaining reactions. Deviations in osmolarity or pH can alter molecular shapes and arrest metabolic pathways. Homeostasis maintains the "steady state" required for continuous biochemical efficiency.
D. To support external temperature changes: The body regulates internal temperature through specific thermoregulatory mechanisms like sweating and shivering. While fluid balance supports these efforts, the regulation of chemical concentrations is primarily about internal stability. It protects the body from internal chemical chaos regardless of the weather.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. Muscles and fat: While skeletal muscle contains about 75% water, adipose tissue is uniquely hydrophobic and contains very little water (approximately 10%). A high proportion of fat significantly reduces the total body water percentage. This combination does not represent the highest overall hydration level.
B. Bones and muscles: Cortical bone is relatively dry, containing only about 20% to 30% water within its calcified matrix. While muscle is highly hydrated, the low water content of bone pulls the average down. Soft, metabolically active visceral organs contain much higher percentages of fluid.
C. Kidneys and brain: These organs are highly vascularized and metabolically active, consisting of approximately 80% to 85% water. The brain requires a high fluid content for signaling and protection, while the kidneys process the body's entire fluid volume. They represent the most aqueous tissues in the body.
D. Teeth and skin: Tooth enamel is the hardest and driest substance in the human body, containing almost no water. The skin provides a protective barrier and contains significantly less water than internal organs to prevent excessive evaporative loss. This pair contains the least hydrated tissue in the body.
Correct Answer is B
Explanation
A. It measures the volume of blood plasma only: Osmolality refers to the concentration of particles per kilogram of solvent rather than the total volume of the compartment. Volume is a quantitative measure of space, while osmolality is a qualitative measure of solute density. These are distinct hemodynamic parameters.
B. It is influenced by the balance of solutes and water in the blood: The ratio of dissolved particles, primarily sodium, glucose, and urea, to the volume of water determines the osmotic pressure. High water intake decreases osmolality through dilution. Conversely, water loss through perspiration or diuresis increases the concentration of these solutes.
C. It has no relationship to hydration status: Plasma osmolality is the primary physiological indicator used by the hypothalamus to monitor hydration. Rising osmolality triggers the thirst mechanism and the release of antidiuretic hormone to conserve water. It is the most sensitive marker for systemic water balance.
D. It varies greatly in healthy individuals: Homeostatic mechanisms maintain plasma osmolality within a very narrow range, typically 280 to 295 mOsm/kg. Tight regulation ensures that cells do not experience osmotic shock or volume shifts. Significant variations usually indicate underlying pathological states or severe dehydration.
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