Nokea
Hormone release stops when the stimulus that triggered it – like thirst or high blood sugar is satisfied or corrected. This is called:
- A. positive feedback system
- B. negative feedback system
- C. lock and key system
- D. solar system
Correct Answer: B
Rationale: The correct answer is B: negative feedback system. In a negative feedback system, the body's response to a stimulus works to counteract the initial stimulus, bringing the body back to its set point. In the context of the question, hormone release stops when the stimulus is satisfied, which is characteristic of a negative feedback system. A: Positive feedback system amplifies the initial stimulus rather than counteracting it. C: Lock and key system refers to how enzymes bind to specific substrates, not related to hormone regulation. D: Solar system is unrelated to physiological processes.
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Insulin:
- A. is secreted by the beta cells of the islets of Langerhans.
- B. is secreted by the liver.
- C. raises blood glucose levels.
- D. is released by the pancreas in response to low blood glucose levels.
Correct Answer: A
Rationale: Step-by-step rationale:
1. Insulin is a hormone that regulates blood glucose levels by promoting glucose uptake into cells.
2. Beta cells of the islets of Langerhans in the pancreas are responsible for secreting insulin.
3. Insulin lowers blood glucose levels by enhancing glucose uptake and storage.
4. Therefore, choice A is correct as it accurately identifies the source of insulin secretion.
Summary:
- Choice B is incorrect as the liver does not secrete insulin.
- Choice C is incorrect as insulin lowers blood glucose levels.
- Choice D is incorrect as insulin is released in response to high, not low, blood glucose levels.
Which of the following is NOT a type of hormone stimulus?
- A. hormonal stimulus
- B. humoral stimulus
- C. neural stimulus
- D. receptor-mediated stimulus
Correct Answer: D
Rationale: The correct answer is D, receptor-mediated stimulus. Hormones can be stimulated by hormonal, humoral, or neural factors, but not directly by receptors. Hormonal stimulus involves other hormones triggering hormone release, humoral stimulus involves changing blood levels of ions or nutrients triggering hormone release, and neural stimulus involves direct nerve stimulation triggering hormone release. Receptor-mediated stimulus is not a recognized type of hormone stimulus because hormones do not directly respond to receptors in this context.
In Which of the Following Pairs, the Hormone of Endocrine Glands and Its Primary Action Is Incorrect or Mismatched?
- A. Calcitonin - Lower blood calcium levels
- B. Parathyroid - Raises blood calcium levels
- C. Somatostatin - Inhibits release of glucagon
- D. Melatonin - Regulates the rate of cellular metabolism
Correct Answer: D
Rationale: The correct answer is D - Melatonin - Regulates the rate of cellular metabolism. Melatonin is a hormone primarily involved in regulating sleep-wake cycles, not cellular metabolism.
A: Calcitonin - Lower blood calcium levels - Correct. Calcitonin is released by the thyroid gland to lower blood calcium levels.
B: Parathyroid - Raises blood calcium levels - Correct. Parathyroid hormone is released by the parathyroid glands to raise blood calcium levels.
C: Somatostatin - Inhibits release of glucagon - Correct. Somatostatin inhibits the release of glucagon and insulin.
Endocrine glands differ from exocrine glands in that:
- A. Endocrine glands are ductless and exocrine glands release secretions at the body's surface or into ducts.
- B. Endocrine glands release hormones, whereas exocrine glands release waste.
- C. Endocrine glands are formed by epithelial tissue, but exocrine glands are primarily connective tissue.
- D. Endocrine glands are all interconnected; whereas exocrine glands act completely independently.
Correct Answer: A
Rationale: The correct answer is A because endocrine glands are ductless and release hormones directly into the bloodstream to reach target organs, while exocrine glands release their secretions through ducts onto the body's surface or into specific locations. This distinction is crucial as it highlights the mode of transportation of their secretions. Choices B, C, and D are incorrect because exocrine glands do not release waste; they release enzymes, sweat, etc. Exocrine glands can be formed by various types of tissues, not just connective tissue. Additionally, exocrine glands do not necessarily act completely independently; they can be part of a system or network but still release their secretions through ducts.
Which row shows the correct order of reactivity for the elements?
- A. silver, calcium, carbon, potassium
- B. silver, carbon, calcium, potassium
- C. sodium, hydrogen, zinc, gold
- D. sodium, zinc, hydrogen, gold
Correct Answer: D
Rationale: The correct order of reactivity for elements is based on their tendency to lose electrons. In this case, sodium is the most reactive as it readily loses an electron to form a stable ion. Zinc is less reactive compared to sodium but more reactive than hydrogen and gold. Hydrogen is less reactive than both zinc and sodium. Gold is the least reactive among the options given. Therefore, the correct order of reactivity is sodium > zinc > hydrogen > gold, which matches option D. Choices A, B, and C do not follow the correct order of reactivity for the elements listed, making them incorrect.