This is a branch of the left coronary arteries which supplies the LEFT ATRIUM, posterior lateral surface of the left ventricle.

Correct Answer: B

Rationale: The correct answer is B, the Left circumflex artery. This artery branches off the left coronary artery and supplies the left atrium and the posterior lateral surface of the left ventricle. The Left anterior descending artery (C) supplies the anterior surface of the left ventricle. The Right coronary artery (A) supplies the right atrium and right ventricle. The Posterior descending artery (D) is a branch of the right coronary artery and supplies the posterior wall of the left ventricle. Therefore, B is the correct answer based on the specific areas supplied by each artery.

Correct Answer: B

Rationale: The correct answer is B (Approximately 4 to 8 L per minute) because the average cardiac output in a healthy adult at rest is around 5 L per minute. This range of 4 to 8 L per minute encompasses the typical cardiac output values. Choice A (Approximately 4 to 6 L per minute) is too narrow and excludes the upper range, while Choice C (Approximately 5 to 8 L per minute) is slightly broader but still within the acceptable range. Choice D (Approximately 3 to 7 L per minute) is too low and does not cover the full spectrum of average cardiac output values.

Correct Answer: A

Rationale: The correct answer is A: Frank-Starling's Law. This law states that within physiologic limits, the greater the myocardial fiber stretch, the more forceful the ventricular contraction, leading to increased stroke volume. This is because increased fiber stretch results in optimal overlap of actin and myosin filaments in the sarcomeres, enhancing contractile force. Summary: B: Automaticity refers to the ability of cardiac cells to spontaneously generate electrical impulses. C: Contractility is the intrinsic ability of cardiac muscle to generate force. D: Excitability refers to the ability of cardiac cells to respond to electrical stimuli.

Correct Answer: D

Rationale: The correct answer is D: Epinephrine. Epinephrine acts as a central vasoconstrictor by constricting blood vessels in vital organs to redirect blood flow to muscles during fight-or-flight response. It also acts as a peripheral vasodilator by dilating blood vessels in skeletal muscles to increase oxygen delivery. Parasympathetic nervous system (A) mainly promotes relaxation, sympathetic nervous system (B) typically causes vasoconstriction, and dopamine (C) has limited vasoactive effects.

Correct Answer: C

Rationale: The correct answer is C, the left ventricle. The left ventricle receives oxygenated blood from the lungs through the left atrium and pumps it to the rest of the body via the aorta. This chamber has thicker muscular walls compared to the right ventricle to generate enough force to propel blood throughout the body. The left atrium receives oxygenated blood from the lungs but does not pump blood out to the body. The right atrium receives deoxygenated blood from the body and sends it to the right ventricle, which then pumps it to the lungs for oxygenation. Therefore, choices A, B, and D are incorrect as they do not accurately describe the function of the heart chamber that receives oxygenated blood from the lungs and pumps it to the rest of the body.