straightening the elbow by lowering the hand affects which of the following muscles
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ATI RN

ATI Anatomy and Physiology

1. Lowering the hand by straightening the elbow affects which of the following muscles?

Correct answer: B

Rationale: Lowering the hand by straightening the elbow is the action of extending the forearm, which is primarily done by the triceps brachii muscle. The triceps brachii is the main extensor muscle of the elbow joint. The biceps brachii is responsible for flexing the elbow, not extending it, making it an incorrect choice. Brachialis is a strong elbow flexor, and brachioradialis helps in flexing the elbow and pronating the forearm, so they are not the primary muscles involved in straightening the elbow.

2. Is a cell the basic unit of structure and function of an organism?

Correct answer: A

Rationale: The correct answer is A: True. A cell is indeed the basic unit of structure and function of an organism. Cells are the smallest independently functioning unit in the structure of an organism and carry out vital functions necessary for life. Choice B, False, is incorrect because cells are universally recognized as the fundamental unit of life. Choice C, Not Sure, is incorrect as the role of a cell as the basic unit of an organism's structure and function is a well-established scientific fact. Choice D, None of the above, is incorrect as the statement provided in the question is true.

3. 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.

4. Which of the following may indicate hypersecretion of thyroid hormone?

Correct answer: A

Rationale: Weight loss is a common symptom of hyperthyroidism, which is characterized by an excess secretion of thyroid hormone. This increased metabolic rate can lead to weight loss despite normal or increased appetite. Bradycardia (slow heart rate), cold intolerance, and lethargy are more commonly associated with hypothyroidism, where there is an insufficient production of thyroid hormone. Therefore, choices B, C, and D are incorrect in the context of hypersecretion of thyroid hormone.

5. Positive feedback mechanisms usually result in

Correct answer: C

Rationale: Positive feedback mechanisms usually result in unstable conditions. In a positive feedback loop, the output enhances or amplifies the changes that are occurring, leading to a deviation from the initial set point. Therefore, positive feedback does not bring values back towards the set point (Choice A). Choice B is incorrect because positive feedback does not promote stability around a set point. Choice D is also incorrect as positive feedback mechanisms typically do not lead to long-term changes; instead, they intensify the initial change, causing instability.

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