Correct Answer: A

Rationale: The correct answer is Chronic Obstructive Pulmonary Disease (COPD). COPD is a chronic lung condition that encompasses chronic bronchitis and emphysema, causing airflow obstruction from the lungs. Pneumonia (choice B) is an infection in the lungs, while asthma (choice C) is characterized by airway inflammation and constriction. Tuberculosis (choice D) is a bacterial infection that primarily affects the lungs but is distinct from COPD.

Correct Answer: A

Rationale: Baroreceptors are the correct answer. Baroreceptors are specialized sensory receptors that detect changes in pressure within blood vessels. They are primarily located in the aortic arch and carotid sinuses, where they play a crucial role in regulating blood pressure. Chemoreceptors (Choice B) are receptors that detect chemical changes, not pressure changes. Nociceptors (Choice C) are responsible for detecting painful stimuli. Mechanoreceptors (Choice D) respond to mechanical stimuli such as touch, pressure, and vibration, but they are not specifically located in the aortic and carotid bodies.

Correct Answer: B

Rationale: The correct answer is B: Approximately 70 mL of blood per beat. The stroke volume of the heart is typically around 70 mL, indicating the volume of blood ejected from the left ventricle with each contraction. Choices A, C, and D are incorrect as they do not represent the standard approximate stroke volume of the heart, which is around 70 mL per beat.

Correct Answer: A

Rationale: The correct answer is A, Excitability. Excitability is the ability of cardiac cells to respond to a stimulus by initiating a cardiac impulse. Choice B, Contractility, refers to the ability of cardiac muscle to shorten forcibly. Choice C, Rhythmicity, refers to the cardiac muscle's ability to contract rhythmically. Choice D, Conductivity, refers to the ability of the heart's cells to conduct electrical impulses.

Correct Answer: A

Rationale: Acetylcholine is the correct answer. It is a neurotransmitter released by the parasympathetic nervous system that can decrease heart rate. Norepinephrine, dopamine, and serotonin are neurotransmitters that usually have different effects on the body and are not specifically associated with decreasing heart rate. Norepinephrine, for example, is often related to the fight-or-flight response and can increase heart rate.