Where is the impulse from the SA node delayed, enabling atrial contraction to complete before the ventricles are stimulated and contract?

Correct Answer: A

Rationale: The impulse from the SA node is delayed at the AV node to allow time for the atria to contract before the ventricles. The AV node acts as a gatekeeper, slowing down the electrical signal before transmitting it to the Bundle of His, which then conducts the signal to the ventricles. This delay ensures proper coordination between atrial and ventricular contractions. Choices C and D are incorrect as the SA node does not delay its own impulse, and the aorta is not involved in the conduction system.

Correct Answer: A

Rationale: The correct answer is A: Afterload. Afterload refers to the amount of tension the ventricle must develop during contraction to eject blood into the aorta. It is the resistance the heart must overcome to eject blood. Preload (B) is the stretch on the heart muscle before contraction. Automaticity (C) refers to the heart's ability to generate electrical impulses. Ejection fraction (D) is the percentage of blood pumped out of the ventricle with each heartbeat.

Correct Answer: A

Rationale: The correct answer is A: Sympathetic nervous system. The sympathetic nervous system releases norepinephrine, which acts as a central vasodilator by dilating blood vessels in the heart and skeletal muscles. It also acts as a peripheral vasoconstrictor by constricting blood vessels in other areas to redirect blood flow to vital organs during fight-or-flight responses. B: Parasympathetic nervous system is incorrect as it primarily promotes rest and digestion, not vasodilation or vasoconstriction. C: Norepinephrine is incorrect as it acts as a peripheral vasoconstrictor, not a central vasodilator. D: Acetylcholine is incorrect as it primarily functions in the parasympathetic nervous system and is not associated with central vasodilation or peripheral vasoconstriction.

Correct Answer: A

Rationale: Step 1: Heart failure is characterized by the heart's inability to effectively pump blood, leading to fluid buildup and swelling. Step 2: Cardiomyopathy is a disease of the heart muscle, which may contribute to heart failure but is not the direct cause of fluid buildup. Step 3: Angina is chest pain due to reduced blood flow to the heart, not directly related to fluid buildup. Step 4: Myocarditis is inflammation of the heart muscle, which can lead to heart failure but is not the primary cause of fluid accumulation. Summary: Heart failure is the correct answer as it directly relates to the inability of the heart to pump blood effectively, leading to fluid accumulation. Cardiomyopathy, angina, and myocarditis are related to heart health but do not directly cause fluid buildup in the body.

Correct Answer: A

Rationale: The correct answer is A: Cardiac output. Cardiac output is the total amount of blood pumped by the heart in a minute. It is calculated by multiplying the heart rate (beats per minute) by the stroke volume (amount of blood pumped per beat). This measurement gives an indication of how effectively the heart is functioning in delivering oxygenated blood to the body. B: Stroke volume is the amount of blood pumped by the heart in each beat, not the total amount in a minute. C: End-diastolic volume is the amount of blood in the ventricles before contraction, not the total amount pumped in a minute. D: Ejection fraction is the percentage of blood pumped out of the ventricles with each contraction, not the total amount in a minute.