Which of the following will NOT be triggered by the release of acetyl choline in the synapse at the neuromuscular junction during muscle contraction?

Correct Answer: C

Rationale: At the neuromuscular junction, acetylcholine release initiates muscle contraction by binding to receptors on the muscle membrane, causing depolarization and an action potential that propagates along the fiber. This triggers calcium release from the sarcoplasmic reticulum, which binds to troponin, shifting tropomyosin to expose myosin-binding sites on actin, enabling contraction. These events form a direct cascade from acetylcholine's action. However, ATP binding to the myosin head occurs later in the cross-bridge cycle, detaching myosin from actin after a power stroke, a process not directly initiated by acetylcholine but part of the contraction-relaxation cycle powered by ATP hydrolysis. This distinction highlights that while calcium and actin exposure are immediate downstream effects, ATP's role is a subsequent step, reliant on energy dynamics rather than the initial synaptic signal, making it the exception in this sequence.

Correct Answer: B

Rationale: Muscle glycogen provides the most energy during moderate to high-intensity exercise, like running or cycling, via glycolysis, rapidly yielding ATP anaerobically or aerobically. Stored in muscle (300-500g), it's directly accessible, powering sustained efforts as intensity limits fat oxidation. Liver glycogen (100g) supports blood glucose but depletes fast, less impactful locally. Intramuscular lipids contribute at lower intensities, insufficient for high demand. Adipose tissue lipids, vast but slow to mobilize, dominate in prolonged low-intensity states, not moderate-high. Muscle glycogen's quantity and rapid breakdown distinguish it, critical for intense performance, unlike smaller or slower sources.

Correct Answer: C

Rationale: Parallel fascicles run along a muscle's long axis, as in sartorius, maximizing range of motion with fibers aligned end-to-end. Circular fascicles (e.g., orbicularis oris) encircle openings, not axial. Pennate fascicles (e.g., deltoid) angle into a tendon, increasing force, not parallel. 'Rectus' describes straight muscles (e.g., rectus abdominis), often parallel, but parallel is the broader term. This arrangement suits lengthy, strap-like muscles, distinguishing it from circular closure, pennate power, or rectus specificity, key for motion range.

Correct Answer: D

Rationale: Diaphragm and scalenes aid respiration. The diaphragm contracts, expanding the chest for inhalation, while scalenes elevate upper ribs, assisting inspiration. Intertransversarii and interspinales stabilize vertebrae, not breathing. Semispinalis muscles extend the spine, not respiratory. Trapezius and rhomboids move the scapula, unrelated to lungs. Diaphragm-scalene synergy drives breathing, distinguishing them, key for respiratory mechanics.

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.