Lactic acid is produced

Correct Answer: C

Rationale: Lactic acid accumulates in fatigued skeletal muscles when oxygen supply lags demand, shifting metabolism to anaerobic glycolysis. Normally, pyruvate from glucose enters mitochondria for aerobic respiration, yielding ATP efficiently. During intense exercise, oxygen depletion forces pyruvate conversion to lactate via lactate dehydrogenase, releasing NAD+ to sustain glycolysis and ATP production, though less efficiently. This occurs in skeletal muscle, not exclusively cardiac, which relies more on aerobic pathways. Rested muscles with oxygen use aerobic metabolism, avoiding lactate buildup. Fatigued muscles with oxygen continue aerobic respiration, not glycolysis. Rested muscles lacking oxygen are hypothetical, as rest implies oxygen availability. Exercise physiology confirms lactate rises in anaerobic conditions blood levels can jump from 1 to 20 mmol/L in fatigue causing acidity and signaling exhaustion. This adaptive mechanism delays fatigue, distinguishing it from aerobic states or unrelated muscle types, a key insight into metabolic flexibility.

Correct Answer: A

Rationale: Joints are stabilized by structures connecting bones directly. Ligaments are tough, fibrous tissues linking bone to bone, providing stability and limiting excessive movement, like the ACL in the knee. Tendons connect muscle to bone, facilitating movement, not joint union. Muscles generate force but don't join bones structurally. Cartilage cushions joints but doesn't bind bones together. Ligaments are the anatomical answer, as their primary role is maintaining joint integrity, distinguishing them from the other options focused on movement or padding rather than connection.

Correct Answer: A

Rationale: Rheumatic arthritis requires exercises to maintain joint mobility and strength, but they must be tailored to avoid worsening inflammation. Doing them daily, 3-10 times per joint, promotes consistency and flexibility without overexertion, fitting a balanced program. Exercising during active inflammation can damage joints further, as rest is then advised. Continuing past pain risks injury, contradicting pain-as-a-guide principles. Doubling after a missed day could strain joints excessively. The daily repetition approach supports gradual improvement, respecting the condition's need for regular, gentle movement to manage stiffness and function, making it the safest, most effective instruction.

Correct Answer: C

Rationale: A compound fracture, with bone piercing skin, risks bleeding and infection, so the immediate action is stabilizing it. Splinting the leg as it lies immobilizes the fracture, minimizing further damage, blood loss, and pain until medical help arrives. Lying flat might worsen alignment or bleeding without stabilization. A tourniquet is extreme, used only for uncontrolled hemorrhage, not standard here. Straightening the leg risks worsening the injury, driving bone deeper or increasing bleeding. Splinting preserves the current state, aligning with first-aid principles for open fractures, ensuring safety and reducing complications before transport.

Correct Answer: A

Rationale: The insertion is the attachment of a muscle tendon to a movable bone, contrasting with the origin, which is attached to a stationary bone. When a muscle contracts, the insertion moves toward the origin, producing motion. For example, in the quadriceps, the insertion on the tibia moves during knee extension. The diaphragm is a specific muscle, not an attachment type. Compartments refer to muscle groups, not individual attachments. Superficial indicates location, not a connection point. The insertion's role as the movable end is a foundational concept in muscle anatomy, making it the correct answer, as it directly corresponds to the definition provided and distinguishes it from the stationary origin.