Nokea
Which term describes the maintenance of a stable internal environment?
- A. negative feedback
- B. positive feedback
- C. homeostasis
- D. metabolism
Correct Answer: C
Rationale: Homeostasis is the maintenance of a stable internal environment to support optimal physiological functioning. It involves mechanisms that regulate variables within a narrow range. Negative feedback is a key mechanism in maintaining homeostasis by counteracting deviations from set points. Positive feedback amplifies changes and is not involved in maintaining stability. Metabolism refers to the chemical processes in the body and is not specifically related to the maintenance of internal stability. Therefore, the correct answer is C (homeostasis) because it directly relates to the concept of maintaining a stable internal environment through regulatory mechanisms.
You may also like to solve these questions
A 33-year-old woman becomes poisoned after receiving an injection of concentrated botulinum toxin. Which of the following is the main neurochemical mechanism by which this Clostridium toxin causes its effects?
- A. Directly activates all muscarinic and nicotinic receptors
- B. Inhibits ACh release from all cholinergic nerves
- C. Prevents neuronal norepinephrine reuptake
- D. Releases norepinephrine via a nonexocytotic process
Correct Answer: B
Rationale: The correct answer is B: Inhibits ACh release from all cholinergic nerves. Botulinum toxin blocks the release of acetylcholine (ACh) from cholinergic nerve terminals, leading to muscle paralysis. This occurs through the cleavage of SNARE proteins, preventing vesicle fusion and neurotransmitter release. Choice A is incorrect because botulinum toxin does not directly activate receptors. Choice C is incorrect as botulinum toxin does not affect neuronal norepinephrine reuptake. Choice D is incorrect because botulinum toxin does not release norepinephrine via a nonexocytotic process.
The target organs of ADH are the:
- A. adrenal cortex and liver
- B. kidney and blood vessels
- C. liver and kidney
- D. pituitary and thyroid glands
Correct Answer: B
Rationale: The correct answer is B: kidney and blood vessels. ADH, or antidiuretic hormone, acts on the kidney to regulate water reabsorption and maintain fluid balance in the body. It also acts on blood vessels to regulate blood pressure. The other choices are incorrect because ADH does not target the adrenal cortex, liver, pituitary gland, or thyroid gland specifically for its primary functions. ADH primarily acts on the kidney and blood vessels to regulate water balance and blood pressure in the body.
One of the least complicated of the endocrine control systems directly responds to changing blood levels of ions and nutrients. Which of the following describes this mechanism?
- A. the rapid oxidation of carbohydrates
- B. catabolic inhibition
- C. protein synthesis
- D. humoral stimulation
Correct Answer: D
Rationale: The correct answer is D: humoral stimulation. This mechanism directly responds to changing blood levels of ions and nutrients. Humoral stimulation refers to the regulation of hormone secretion in response to changes in blood levels of various substances like ions and nutrients. It is a feedback mechanism that helps maintain homeostasis by adjusting hormone levels based on the body's needs.
A: Rapid oxidation of carbohydrates is not related to endocrine control systems responding to changing blood levels of ions and nutrients.
B: Catabolic inhibition does not directly respond to changing blood levels of ions and nutrients.
C: Protein synthesis is not a mechanism that directly responds to changing blood levels of ions and nutrients.
Thyroid hormone exerts its influence by ________.
- A. entering some cells and binding to intracellular receptors within the nuclei
- B. exerting only a minor effect on body metabolism
- C. causing a reduction in the number of blood vessel adrenergic receptors, and therefore decreasing blood pressure
- D. acting to decrease basal metabolic rate
Correct Answer: A
Rationale: The correct answer is A because thyroid hormone is a lipid-soluble hormone that can diffuse across the cell membrane and bind to intracellular receptors within the nuclei. This binding activates gene transcription, leading to various metabolic effects. Choice B is incorrect because thyroid hormone actually has a significant impact on body metabolism. Choice C is incorrect as thyroid hormone does not directly affect blood vessel adrenergic receptors or blood pressure. Choice D is incorrect as thyroid hormone actually acts to increase basal metabolic rate, not decrease it.
Which row shows the correct labels on the diagram of a leaf section?
- A. cuticle, palisade mesophyll, stoma
- B. epidermis, palisade mesophyll, guard cell
- C. cuticle, spongy mesophyll, guard cell
- D. epidermis, spongy mesophyll, stoma
Correct Answer: A
Rationale: The correct answer is A because the cuticle is the waxy layer on the leaf surface, palisade mesophyll is the layer of elongated cells where photosynthesis occurs, and stoma is the opening for gas exchange. Epidermis is the outer layer, not the cuticle. Spongy mesophyll is below palisade mesophyll, not above it. Guard cells surround stomata, not spongy mesophyll.