How does the respiratory system help stabilize blood pH when CO: levels increase?
By absorbing carbonic acid into tissues
By increasing the respiratory rate to expel CO2
By producing more hydrogen ions
By excreting carbonic acid through sweat
The Correct Answer is B
A. By absorbing carbonic acid into tissues: Carbonic acid is not absorbed into tissues for storage; it exists in equilibrium with dissolved carbon dioxide. Retaining it would lead to a progressive decrease in systemic pH and tissue damage. The body must eliminate the source of the acid rather than sequestering it.
B. By increasing the respiratory rate to expel CO2: Central and peripheral chemoreceptors detect rising partial pressures of carbon dioxide and trigger the medullary respiratory center. This hyperventilation increases alveolar gas exchange, blowing off the excess carbon dioxide. This process reduces the concentration of carbonic acid and raises pH.
C. By producing more hydrogen ions: Increasing hydrogen ion production would exacerbate the acidotic state and further lower the blood pH. The goal of the respiratory system is to remove the chemical precursor of acidity. Hydrogen ions are a product of carbon dioxide retention, not a tool for stabilization.
D. By excreting carbonic acid through sweat: Sweating is a mechanism for thermoregulation and the excretion of small amounts of electrolytes and urea. It is not a significant pathway for the elimination of carbon dioxide or the regulation of acid-base balance. Respiratory gases must be exchanged via the pulmonary membrane.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. PTH, calcitriol, and calcitonin: Parathyroid hormone raises serum calcium, while calcitriol (active Vitamin D) increases intestinal absorption. Calcitonin serves as a minor antagonist to PTH by promoting bone deposition. Together, they regulate the flux of ions between bone, gut, and kidneys.
B. Thyroxine, epinephrine, and norepinephrine: These hormones regulate basal metabolic rate and the sympathetic "fight or flight" response. While they influence overall physiology, they do not possess specific receptors or mechanisms for mineral homeostasis. They do not directly control calcium or phosphate concentrations.
C. Estrogen, testosterone, and aldosterone: Sex steroids influence bone density over time, but they do not provide the acute regulation of mineral balance. Aldosterone is strictly a regulator of sodium and potassium. They lack the rapid feedback loops required to maintain ionized calcium levels.
D. Insulin, glucagon, and cortisol: These hormones are primarily involved in the regulation of carbohydrate, lipid, and protein metabolism. Cortisol can lead to bone loss in chronic excess, but it is not a primary homeostatic regulator. They do not manage the day-to-day phosphate balance.
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.
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