____ is the most significant solute in determining the distribution of water among fluid compartments.
K+
Na+
Mg+2
CI-
Ca+2
The Correct Answer is B
A. K+: Potassium is the most abundant intracellular cation and is crucial for maintaining the resting membrane potential of excitable tissues. While it determines the volume of the intracellular fluid, it does not dominate the overall distribution of water between the major fluid compartments. Its levels are tightly regulated.
B. Na+: Sodium is the most abundant cation in the extracellular fluid and accounts for approximately 90 percent of its osmotic pressure. Because water follows solutes, the total body sodium content is the primary determinant of extracellular fluid volume. It is the "osmotic magnet" for water distribution.
C. Mg+2: Magnesium is primarily an intracellular cation that serves as a cofactor for numerous enzymatic reactions. Its concentration in the extracellular fluid is relatively low compared to sodium or chloride. It does not exert a significant osmotic pull on the total volume of body water.
D. Cl-: Chloride is the most prevalent extracellular anion and often follows sodium to maintain electrical neutrality. While it contributes to osmotic pressure, its movement is generally secondary to the active transport of sodium. Sodium remains the primary driver of the osmotic gradients that move water.
E. Ca+2: Calcium ions are essential for blood clotting, neurotransmitter release, and muscle contraction. Extracellular calcium levels are kept within a very narrow range and are too low to significantly influence the total osmotic pressure of the plasma. It is not a major factor in fluid distribution.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. helps maintain homeostasis by controlling the composition, volume, and pressure of blood: The kidneys filter the blood to regulate electrolyte balance and total body water. By adjusting the amount of water excreted, the system directly influences blood volume and long-term blood pressure. This is a primary physiological role of the renal system.
B. regulates blood glucose levels and produces hormones: The kidneys perform gluconeogenesis during prolonged fasting to maintain plasma glucose. They also endocrine functions such as producing erythropoietin for red blood cell synthesis and calcitriol for calcium regulation. These metabolic and hormonal activities are essential renal functions.
C. maintains blood osmolarity: The urinary system regulates the loss of water and solutes to keep blood osmolarity near 300 mOsm/L. This prevents cellular dehydration or swelling by controlling the osmotic pressure of the extracellular fluid. This balance is achieved through the action of antidiuretic hormone.
D. eliminates solid, undigested wastes and excretes carbon dioxide, water, salts, and heat: The elimination of solid, undigested waste is a function of the gastrointestinal system, not the urinary system. Carbon dioxide excretion is primarily handled by the respiratory system through gas exchange in the lungs. The urinary system focuses on soluble metabolic nitrogenous wastes.
Correct Answer is D
Explanation
A. The sister chromatids are separated from each other: During the first meiotic division, the goal is to reduce the chromosome number by separating homologous pairs. The separation of sister chromatids is the defining event of meiosis 2 or mitosis, not meiosis 1. In meiosis 1, sister chromatids remain attached at the centromere as they move toward the poles.
B. Portions of maternal chromosomes crossover with equivalent portions of paternal chromosomes: Synapsis and crossing over occur during prophase 1, where non-sister chromatids of homologous chromosomes exchange genetic material. This process increases genetic diversity by creating new combinations of alleles. It is a hallmark event that occurs exclusively during the first division of meiosis.
C. The homologous chromosomes are separated from each other: Anaphase 1 focuses on pulling apart the pairs of chromosomes inherited from each parent. This ensures that each daughter cell receives only one member of each pair, though each member still consists of two chromatids. This separation is the physical basis for the law of segregation in genetics.
D. A single diploid (2n) nucleus has become two haploid (n) nuclei: Meiosis 1 is referred to as a reductional division because it halves the chromosome count. The starting cell begins with 46 chromosomes in humans, and the resulting daughter cells each contain 23 chromosomes. This transition from diploid to haploid occurs specifically during the cytokinesis following telophase 1.
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