What are the three steps of the 'wave of excitation'?

Correct Answer: D

Rationale: The correct steps of the 'wave of excitation' are the excitation of the atrium, excitement of the ventricle, and relaxation of the ventricle. In the described process, the 'wave of excitation' starts with the discharge from the SA node, leading to the excitation of the atrium. Next, the peak ECG corresponds to the excitement of the ventricle, not its relaxation. Finally, the wave concludes with the relaxation of the ventricle, not its contraction. Therefore, choices A, B, and C are incorrect as they do not accurately describe the sequential steps of the 'wave of excitation' as presented in the extract.

Correct Answer: C

Rationale: The primary purpose of the essay is to inform the reader about how the cardiovascular system regulates blood pressure. The essay provides detailed explanations about the components of the cardiovascular system that regulate blood pressure, such as baroreceptors, chemoreceptors, and the kidneys. Choices A and B are incorrect because the essay does not focus on discussing the dangers of high blood pressure or its correlation with a higher risk of heart attack. Choice D is incorrect as the essay does not aim to persuade the reader to control their blood pressure but rather to educate them on the regulatory mechanisms of the cardiovascular system.

Correct Answer: B

Rationale: The correct answer is B because it provides a comprehensive summary of the passage, explaining how the cardiovascular system regulates blood pressure through baroreceptors, chemoreceptors, and the kidneys. Choice A is incorrect as it only focuses on the heart and kidneys without mentioning the broader cardiovascular system. Choice C is incorrect as it solely emphasizes the role of baroreceptors in regulating blood pressure. Choice D is incorrect as it oversimplifies the role of chemoreceptors in monitoring oxygen levels without mentioning their impact on blood pressure regulation.

Correct Answer: A

Rationale: The correct answer is A. Baroreceptors and chemoreceptors send impulses from the arteries, while the kidneys control blood volume. Baroreceptors and chemoreceptors are responsible for monitoring blood pressure by sensing changes in pressure, oxygen levels, carbon dioxide levels, and pH within the arteries. They send out impulses to raise or lower blood pressure accordingly. On the other hand, the kidneys play a crucial role in regulating blood volume by absorbing salts and water and removing waste products. This key difference highlights that while baroreceptors and chemoreceptors are involved in monitoring and regulating blood pressure, the kidneys primarily focus on controlling blood volume. Choice B is incorrect because it inaccurately states that baroreceptors and chemoreceptors help maintain blood volume, which is not their primary function. Choice C is incorrect as it provides an inaccurate comparison between the roles of baroreceptors, chemoreceptors, and the kidneys. Choice D is incorrect as it wrongly associates the location of baroreceptors and chemoreceptors with the adrenal cortex, which is not accurate.

Correct Answer: D

Rationale: In this context, 'ideal' means perfect. The human body provides a perfect environment for many microbes, as stated in the extract. It is the immune system's role to keep these microbes out or destroy them. The other choices are incorrect: 'thoughtful' does not fit the context of the sentence, 'confined' and 'hostile' are not synonymous with 'ideal' in this context.