ATI RN
Questions About Muscular System with Answers Questions
Question 1 of 5
What is the outer layer of the kidney?
Correct Answer: B
Rationale: The kidney's structure is divided into distinct regions, each with specific roles in filtration and urine production. The outermost layer is a granular region containing glomeruli networks of capillaries where blood filtration begins along with proximal and distal tubules that reabsorb nutrients and water. This area, known as the cortex, contrasts with the medulla, which lies deeper and contains renal pyramids for urine concentration. The nephron, while spanning both regions, is the functional unit, not a layer, and pyramids are medullary structures. The cortex's role in initiating filtration via glomeruli and its superficial position make it the outer layer, distinguishing it from deeper structures involved in later urine processing stages. This anatomical arrangement ensures efficient blood processing and waste excretion, with the cortex's position facilitating its primary filtration function.
Question 2 of 5
In the classification of two organisms, which of the following is the best evidence of a close relationship?
Correct Answer: B
Rationale: Close evolutionary relationships are best shown by genetic similarity. Amino acid sequences in proteins, encoded by DNA, reflect shared ancestry highly conserved sequences indicate recent divergence, as with hemoglobin in mammals. Bone structure suggests relation but converges in unrelated species (e.g., bird and bat wings). Reproduction and respiration methods vary widely even among kin. Protein sequences' molecular precision, tied to genetic heritage, outweighs morphological or functional traits, making it the gold standard in phylogenetic analysis.
Question 3 of 5
Equal armed balance is balanced when 20 washers are on one side, and 10 bolts are on the other. Four bolts are added to one side. How many washers must be added to the next side to maintain balance?
Correct Answer: B
Rationale: An equal-armed balance requires equal torque (weight × distance) on both sides. Initially, 20 washers balance 10 bolts, so one bolt equals two washers in weight (20/10 = 2). Adding four bolts increases that side's weight by four bolts, equivalent to 4 × 2 = 8 washers. To maintain balance, eight washers must be added to the other side, keeping total 'washer-equivalents' equal (20 + 8 = 28 vs. 10 × 2 + 4 × 2 = 28). Other options misalign this ratio, making eight the precise counterbalance.
Question 4 of 5
Once myosin binds to actin, heads change shape and slide the This is the sliding filament theory.
Correct Answer: D
Rationale: Myosin heads bind actin, change shape via ATP hydrolysis, and slide actin toward the sarcomere's center, the core of sliding filament theory, shortening the muscle. Actin doesn't slide myosin it's pulled. Troponin regulates, not slides, myosin or actin it shifts tropomyosin. Myosin sliding actin defines the power stroke, distinguishing it from regulatory or reversed actions, essential for contraction mechanics.
Question 5 of 5
During muscle cell contraction, what happens because of $\mathrm{Ca}^{++}$binding to troponin?
Correct Answer: A
Rationale: Calcium drives contraction by binding troponin, a thin filament protein. This binding alters troponin's shape, shifting tropomyosin away from actin's myosin-binding sites, exposing them for cross-bridge formation. Acetylcholine triggers the initial nerve signal, not calcium's role. Cross-bridge disengagement follows ATP binding, not calcium's action, and ATP hydrolysis energizes myosin beforehand. Calcium's specific effect on troponin unveils actin sites, enabling the sliding filament mechanism, a pivotal step distinguishing it from nerve initiation or energy cycles in muscle physiology.