which of the following illustrates a positive feedback mechanism
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ATI Anatomy and Physiology Online Practice

1. Which of the following illustrates a positive feedback mechanism?

Correct answer: B

Rationale: The correct answer is uterine contractions during childbirth. This is an example of a positive feedback mechanism where the initial stimulus (contractions) leads to an increase in intensity and frequency, ultimately resulting in childbirth. In contrast, choices A, C, and D (maintaining blood pressure, body temperature control, and control of blood sugar) are examples of negative feedback mechanisms. These mechanisms work to maintain stability by counteracting any deviations from the set point, rather than amplifying the response like in a positive feedback mechanism.

2. Ceroid pigments and lipofuscin accumulate with aging, impairing a cell's ability to withstand the damaging effects of oxygen free radicals.

Correct answer: A

Rationale: The statement provided in the question is true. Ceroid pigments and lipofuscin are products of cellular damage and aging. These substances accumulate within cells over time and can impair cellular functions, including the ability to withstand the damaging effects of oxygen free radicals. Choice B, 'False,' is incorrect because the accumulation of ceroid pigments and lipofuscin does indeed impair a cell's ability to deal with oxidative stress. Choices C and D are also incorrect as the statement is true.

3. The transition from a hunter-gatherer to an agricultural lifestyle greatly changed the types of diseases and injuries that early peoples suffered.

Correct answer: A

Rationale: The correct answer is True. The transition from a hunter-gatherer to an agricultural lifestyle did indeed greatly change the types of diseases and injuries that early peoples suffered. With the shift to agriculture came increased sedentism, population density, and interaction with domesticated animals, leading to the emergence of new diseases and health challenges. Choice B is incorrect because the statement is true based on historical and archaeological evidence. Choice C is incorrect as there is historical data supporting the impact of this transition. Choice D is incorrect as it is not applicable since all options do not hold true in this context.

4. Is cadaver dissection against the law in the U.S.?

Correct answer: B

Rationale: Cadaver dissection is not against the law in the U.S. In fact, cadaver dissection is a common practice in medical schools and research institutions for educational and research purposes. The correct answer is 'False' because there are specific regulations and ethical guidelines that govern the use of cadavers for dissection. Choice C, 'Not Sure,' is incorrect as the legality of cadaver dissection is a well-established fact. Choice D, 'None of the above,' is also incorrect as one of the provided options is indeed correct.

5. Which of the following valves prevents backflow of blood from the right ventricle into the right atrium of the heart?

Correct answer: B

Rationale: The correct answer is the tricuspid valve. The tricuspid valve is located between the right atrium and the right ventricle of the heart. Its main function is to prevent the backflow of blood from the right ventricle into the right atrium during the heart's pumping cycle. Choice A, the aortic valve, is responsible for preventing backflow from the aorta into the left ventricle. Choice C, the pulmonic valve, prevents backflow from the pulmonary artery into the right ventricle. Choice D, the mitral valve, prevents backflow from the left ventricle into the left atrium.

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