Nokea
Which of the following is NOT a mechanism of hormone action?
- A. plasma membrane permeability changes
- B. cellular mutations occur
- C. enzymes are activated or inactivated
- D. mitosis is stimulated
Correct Answer: B
Rationale: The correct answer is B: cellular mutations occur. Hormones typically act through binding to specific receptors on target cells to initiate a signaling cascade. This process does not involve inducing mutations in the cell's DNA. Plasma membrane permeability changes, enzyme activation/inactivation, and stimulation of mitosis are all well-established mechanisms of hormone action. Therefore, B is the correct answer as it does not align with the usual mechanisms by which hormones exert their effects.
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Which of the following hormones are responsible for the 'fight-or-flight' response?
- A. Epinephrine and norepinephrine.
- B. Insulin and glucagon.
- C. Esrtogen and progesterone.
- D. Thyroxin and melatonin.
Correct Answer: A
Rationale: The correct answer is A: Epinephrine and norepinephrine. These hormones are released by the adrenal glands during stressful situations to trigger the 'fight-or-flight' response. They increase heart rate, blood pressure, and energy production to prepare the body for action. Insulin and glucagon (B) regulate blood sugar levels. Estrogen and progesterone (C) are female sex hormones. Thyroxin and melatonin (D) are involved in metabolism and sleep regulation, respectively. Therefore, only A directly relates to the physiological response of 'fight-or-flight'.
Enlargement of the thyroid gland:
- A. is called a goiter.
- B. causes Addisonian crisis.
- C. makes a person appear cushingoid.
- D. causes hypocalcemic tetany.
Correct Answer: A
Rationale: Step-by-step rationale for why choice A is correct:
1. Enlargement of the thyroid gland is known as a goiter.
2. A goiter can result from various conditions like iodine deficiency or thyroid disorders.
3. It is a common sign of thyroid dysfunction.
4. Goiter may or may not cause symptoms depending on the underlying cause.
5. Therefore, choice A is the correct answer.
Summary:
- Choice B (Addisonian crisis) is incorrect as it is associated with adrenal insufficiency, not thyroid enlargement.
- Choice C (cushingoid appearance) is incorrect as it is related to excess cortisol production, not thyroid enlargement.
- Choice D (hypocalcemic tetany) is incorrect as it is due to low calcium levels, not thyroid enlargement.
Name the gland that is located at the base of the throat, just inferior to the laryngeal prominence (Adam's apple).
- A. Pituitary.
- B. Pineal gland.
- C. Hypothalamus.
- D. Thyroid.
Correct Answer: D
Rationale: The correct answer is D: Thyroid. The thyroid gland is located at the base of the throat, just below the Adam's apple. It is responsible for producing thyroid hormones that regulate metabolism and various bodily functions. The pituitary gland (A) is located in the brain, the pineal gland (B) is located in the brain as well, and the hypothalamus (C) is also in the brain. These glands play crucial roles in hormone regulation, but they are not located at the base of the throat like the thyroid gland.
The most common second messengers for peptide hormones are ______ and _____.
- A. peptide hormones and calcium.
- B. calcium and glucose.
- C. cAMP and calcium.
- D. cAMP and sodium.
Correct Answer: C
Rationale: The correct answer is C: cAMP and calcium. Peptide hormones bind to their receptors on the cell surface, activating G-proteins which then trigger the production of cAMP as a second messenger. cAMP then further activates protein kinases to initiate various cellular responses. Calcium is also a common second messenger in peptide hormone signaling pathways, regulating processes like muscle contraction and gene expression. Choice A is incorrect because peptide hormones themselves are not second messengers. Choice B is incorrect as glucose is not a common second messenger for peptide hormones. Choice D is incorrect as sodium is not typically involved in peptide hormone signaling pathways.
This hormone stimulates osteoclastic activity, causing bone resorption.
- A. Calcitonin
- B. Androgen
- C. PTH
- D. Thyroxine
Correct Answer: C
Rationale: The correct answer is C: PTH. Parathyroid hormone (PTH) stimulates osteoclastic activity, leading to bone resorption. PTH plays a crucial role in regulating calcium levels in the blood. When calcium levels are low, PTH is released to stimulate the release of calcium from bones through osteoclast activity.
A: Calcitonin actually inhibits osteoclastic activity, promoting bone formation.
B: Androgen is a male sex hormone and does not directly influence bone resorption.
D: Thyroxine is a thyroid hormone that regulates metabolism and does not directly affect bone resorption.