Which heart chamber ejects blood into the systemic arterial circulation via the aorta?

Correct Answer: D

Rationale: The correct answer is D, Left ventricle. The left ventricle is responsible for ejecting oxygenated blood into the systemic arterial circulation via the aorta. It receives oxygen-rich blood from the left atrium and pumps it out through the aorta to the rest of the body. Rationale: 1. The left ventricle receives blood from the left atrium, which has already been oxygenated in the lungs. 2. It is the chamber that generates the highest pressure to propel blood into the systemic circulation. 3. The aorta is the main artery that carries oxygenated blood away from the heart to the body. 4. The right atrium and right ventricle are involved in pumping deoxygenated blood to the lungs for oxygenation, not into the systemic circulation. 5. The left atrium receives oxygenated blood from the lungs but does not directly eject blood into the systemic arterial circulation.

Correct Answer: C

Rationale: The correct answer is C: Automaticity. Automaticity refers to the ability of the heart to generate electrical impulses spontaneously, without external stimulation. This allows the heart to initiate its own contractions independently of external influences. Contractility (A) refers to the ability of the heart muscle to contract in response to an electrical stimulus. Excitability (B) refers to the ability of cardiac cells to respond to an electrical stimulus. Rhythmicity (D) refers to the regularity of the heart's electrical impulses. Thus, C is the correct answer as it specifically addresses the heart's ability to generate impulses spontaneously.

Correct Answer: A

Rationale: The correct answer is A: Stroke volume. Stroke volume is the amount of blood ejected by the left ventricle into the aorta per beat. Preload (end-diastolic volume), contractility, and afterload influence stroke volume. Cardiac output (B) is the total volume of blood pumped by the heart per minute. End-diastolic volume (C) is the volume of blood in the ventricle before contraction. Ejection fraction (D) is the percentage of blood ejected from the ventricle during systole.

Correct Answer: A

Rationale: The correct answer is A: Norepinephrine. Norepinephrine is released by the sympathetic nervous system (SNS) to increase heart rate and the force of contraction. This neurotransmitter acts on beta-1 adrenergic receptors in the heart, leading to these effects. Epinephrine (choice B) is also released by the SNS and acts similarly to norepinephrine but is not as specific for the heart's beta-1 receptors. Dopamine (choice C) primarily acts as a precursor to norepinephrine and epinephrine and does not directly increase heart rate or force of contraction. Acetylcholine (choice D) is released by the parasympathetic nervous system and decreases heart rate and the force of contraction.

Correct Answer: A

Rationale: The correct answer is A: Cardiac Index. Cardiac Index is a more accurate indicator of tissue perfusion as it takes into account the individual's body surface area, providing a more standardized measure. It is calculated by dividing the cardiac output by body surface area. This normalization allows for a more precise assessment of tissue perfusion compared to just cardiac output alone. The normal range of Cardiac Index is 2.4-4 L/min/m^2. Summary: - Choice B (Stroke volume) is incorrect because it is the volume of blood pumped out by the heart with each heartbeat, not accounting for body surface area. - Choice C (Ejection fraction) is incorrect because it is the percentage of blood ejected from the heart's left ventricle with each heartbeat, not adjusted for body surface area. - Choice D (Cardiac output) is incorrect because it doesn't consider the individual's body surface area, making it less accurate in assessing tissue perfusion.