Which of the following gas is released out during the process of respiration?

Correct Answer: C

Rationale: Carbon dioxide (CO2) is released during respiration, a byproduct of cellular metabolism where glucose and oxygen produce energy, water, and CO2 in mitochondria. This CO2 diffuses from tissues into the blood, is transported to the lungs, and exhaled via alveoli. Oxygen is consumed, not released it enters the blood. Hydrogen isn't a respiratory gas; it's part of water or metabolic intermediates. 'None' is incorrect CO2 expulsion is respiration's hallmark. This process balances blood pH and oxygen levels, critical for homeostasis, distinguishing respiration from photosynthesis, where CO2 is absorbed, a fundamental principle in physiology and gas exchange studies.

Correct Answer: D

Rationale: The auricle, a pouch-like extension of the atrium, increases its filling capacity, allowing more blood storage during diastole, enhancing atrial volume. The ventricle pumps blood, not a storage pouch. The coronary sulcus is a groove for coronary vessels, not a capacity structure. The fossa ovalis, a fetal remnant, doesn't affect volume. Auricles, wrinkled and ear-like, expand atrial space, aiding preload more prominent on the left crucial for optimizing cardiac output, a subtle but significant feature in heart anatomy and function assessment.

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.