Nokea
Maintaining a stable internal environment typically requires
- A. positive feedback mechanisms.
- B. an unstable outside environment.
- C. decreased atmospheric pressure.
- D. negative feedback mechanisms.
Correct Answer: D
Rationale: The correct answer is 'negative feedback mechanisms.' In biological systems, negative feedback mechanisms help maintain homeostasis by counteracting any deviations from the set point. They work to stabilize internal conditions and keep them within a narrow range. On the other hand, positive feedback mechanisms amplify changes and are not involved in maintaining stability. Choice B, 'an unstable outside environment,' is incorrect as internal stability is independent of external conditions like weather. Choice C, 'decreased atmospheric pressure,' is also incorrect as it does not directly relate to internal homeostasis.
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Homeostasis is the body's maintenance of a stable internal environment.
- A. TRUE
- B. FALSE
- C. Not Sure
- D. None of the above
Correct Answer: A
Rationale: Homeostasis refers to the body's ability to maintain a stable internal environment despite external changes. It involves processes that regulate various physiological factors such as temperature, pH, and blood sugar levels within a narrow range. This ensures that the body's cells can function optimally. Therefore, the correct answer is True. Choices B, C, and D are incorrect because homeostasis aims to maintain stability, not instability, in the internal environment.
Signs of aging at the cellular level are
- A. graying hair, waning strength, and wrinkles.
- B. unrepaired DNA and abnormal proteins.
- C. impaired cell division and the ability to break down and recycle worn cell parts.
- D. a fatty liver and clogged blood vessels.
Correct Answer: C
Rationale: The correct answer is 'impaired cell division and the ability to break down and recycle worn cell parts.' Aging at the cellular level involves reduced efficiency in cell division and the breakdown/recycling of cellular components, leading to functional decline. Choices A, B, and D are incorrect because they involve external physical manifestations or organ-specific issues rather than cellular-level changes associated with aging.
Positive feedback mechanisms usually result in
- A. changes returning values away from a set point.
- B. stable conditions around a set point.
- C. unstable conditions.
- D. long-term changes.
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.
In negative feedback mechanisms, changes away from the normal state
- A. stimulate changes in the same direction
- B. inhibit all body reactions
- C. stimulate changes in the opposite direction
- D. stimulate a reduction in all body requirements
Correct Answer: C
Rationale: In negative feedback mechanisms, changes away from the normal state stimulate changes in the opposite direction. This is a fundamental concept in biological systems where the response to a stimulus opposes the initial change, helping to maintain homeostasis. Choice A is incorrect because negative feedback does not stimulate changes in the same direction. Choice B is incorrect because negative feedback does not inhibit all body reactions, but rather specific responses. Choice D is incorrect because negative feedback does not stimulate a reduction in all body requirements, but rather adjusts specific functions to restore balance.
What does magnetic resonance imaging use?
- A. X-rays.
- B. a radio antenna.
- C. radioisotopes.
- D. high-frequency sound waves.
Correct Answer: D
Rationale: Magnetic resonance imaging (MRI) uses high-frequency sound waves to create detailed images of the inside of the body. X-rays (Choice A) use electromagnetic radiation, not sound waves, making it an incorrect choice. A radio antenna (Choice B) is used for communication, not for MRI imaging. Radioisotopes (Choice C) are used in nuclear medicine imaging techniques, not in MRI scans. Therefore, the correct answer is high-frequency sound waves (Choice D) as they are utilized in MRI technology to produce images.