1. Which hormone is primarily responsible for the regulation of plasma glucose levels? a. Insulin b. Glucagon c. Cortisol d. Epinephrine Answer: a. Insulin Rationale: Insulin, produced by the pancreas, is the hormone responsible for lowering blood glucose levels by facilitating the uptake of glucose into tissues. 2. The sinoatrial node is located in which heart chamber? a. Right atrium b. Left atrium c. Right ventricle d. Left ventricle Answer: a. Right atrium Rationale: The sinoatrial node, known as the heart's natural pacemaker, is located in the right atrium and initiates the electrical impulses that set the pace for cardiac rhythm. 3. What is the primary function of the lymphatic system? a. Digestion of fats b. Regulation of body temperature c. Maintenance of fluid balance d. Production of red blood cells Answer: c. Maintenance of fluid balance Rationale: The lymphatic system maintains fluid balance in the body by returning excess tissue fluid to the bloodstream and also plays a role in the immune response. 4. During inhalation, which muscle contracts to increase the volume of the thoracic cavity? a. External obliques b. Internal intercostals c. Diaphragm d. Rectus abdominis Answer: c. Diaphragm