The normal breathing process is controlled by ____________.

Correct Answer: D

Rationale: Normal breathing is controlled by the ventral and dorsal respiratory groups in the medulla and pons. The dorsal group initiates inspiration, stimulating the diaphragm via the phrenic nerve, while the ventral group adjusts forceful breathing, and the pons refines rhythm together maintaining automatic respiration based on CO2 levels. Lungs execute breathing but don't control it they respond to neural signals. This brain stem coordination ensures steady, involuntary breathing, adapting to metabolic needs, a critical autonomic process distinct from voluntary control, foundational in respiratory physiology and clinical monitoring of breathing disorders.

Correct Answer: A

Rationale: The coronary arteries distribute oxygenated blood to the myocardium, branching from the aorta's base to supply cardiac muscle, ensuring its high metabolic demand is met. Coronary veins and the sinus drain deoxygenated blood back to the right atrium, not supply it. The vena cava delivers systemic deoxygenated blood, not to the heart muscle. These arteries left and right encircle the heart, a lifeline for its function, critical in coronary artery disease where blockages starve myocardium, leading to ischemia or infarction.

Correct Answer: D

Rationale: The vagus nerve (cranial nerve X), via parasympathetic fibers, reduces heart rate by releasing acetylcholine, slowing SA node firing and AV conduction, dropping beats from ~100 to ~70 bpm at rest. Cardiac accelerator nerves (sympathetic) increase rate. The hypoglossal nerve controls tongue movement, not heart. The spinal accessory nerve moves neck muscles, irrelevant here. Vagal stimulation, part of the 'rest and digest' response, balances sympathetic drive, a key autonomic regulator, critical in bradycardia and vagal maneuvers to slow tachycardias.

Correct Answer: B

Rationale: A well-trained athlete has higher cardiac reserve (max CO increase), stroke volume (more blood per beat), and heart hypertrophy (thicker myocardium) due to endurance training, enhancing efficiency. Resting cardiac output (~5 L/min) remains similar to sedentary individuals athletes' lower resting heart rate (bradycardia, e.g., 40-60 bpm) offsets higher SV, balancing CO. Higher resting CO isn't typical; demand matches supply. This adaptation optimizes performance, key in sports physiology and assessing training effects.

Correct Answer: D

Rationale: The left atrioventricular valve is called both bicuspid (two cusps) and mitral (mitre-shaped), guarding the left atrium-ventricle junction, preventing backflow. Tricuspid is right-sided. This dual naming reflects its structure and role, key in mitral pathology like prolapse, a synonymous valve identity in heart flow.