Nokea
Secretion of oxytocin is increased by
- A. milk ejection
- B. dilation of the cervix
- C. increased prolactin levels
- D. increased extracellular fluid (ECF) volume
Correct Answer: B
Rationale: Certainly! The secretion of oxytocin is increased by the dilation of the cervix. When the cervix dilates during childbirth, it triggers the release of oxytocin from the posterior pituitary gland. This hormone plays a crucial role in stimulating uterine contractions during labor and delivery. Milk ejection (choice A) is primarily regulated by oxytocin but does not directly increase its secretion. Increased prolactin levels (choice C) stimulate milk production, not oxytocin secretion. Increased extracellular fluid (ECF) volume (choice D) is not directly related to oxytocin secretion.
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If farmers exposed to 'insecticides' ('irreversible' cholinesterase inhibitors) are given medical kits that contain atropine. Which one of the following effects of the cholinesterase inhibitor will NOT be blocked by the atropine?
- A. Bronchoconstriction / bronchospasm
- B. Increased bladder/urinary tract activity
- C. Increased bowel motility (i.e., diarrhea)
- D. Skeletal muscle overstimulation, eventually leading to skeletal muscle paralysis
Correct Answer: D
Rationale: The correct answer is D. Atropine blocks the effects of cholinesterase inhibitors on muscarinic receptors but not on nicotinic receptors, which are responsible for skeletal muscle overstimulation. Atropine can block bronchoconstriction, increased bladder activity, and increased bowel motility as they are mediated by muscarinic receptors. Therefore, the effects on skeletal muscle overstimulation, leading to paralysis, will not be blocked by atropine.
Which one of the following properties makes labetalol different from nearly all the other β-blockers on the market?
- A. Also blocks alpha-adrenergic receptors
- B. Causes strong atropine-like side effects, has same side effects as atropine
- C. Only blocks β1 receptors
- D. Safe for asthmatics because it lacks β2 blocking activity
Correct Answer: A
Rationale: The correct answer is A because labetalol is unique among most β-blockers as it also blocks alpha-adrenergic receptors. This dual action results in vasodilation and reduced blood pressure. Choice B is incorrect as labetalol does not cause atropine-like side effects. Choice C is incorrect as labetalol blocks both β1 and β2 receptors. Choice D is also incorrect as labetalol does have some β2 blocking activity, making it not entirely safe for asthmatics.
Hypersecretion of antidiuretic hormone (ADH) can occur in all of the following situations EXCEPT __________.
- A. damage to the pineal gland
- B. after neurosurgery
- C. after general anesthesia
- D. ectopic ADH secretion by pulmonary cancer
Correct Answer: A
Rationale: The correct answer is A: damage to the pineal gland. The pineal gland does not regulate ADH secretion; it primarily produces melatonin. Neurosurgery and general anesthesia may disrupt the feedback mechanisms controlling ADH release. Ectopic ADH secretion by pulmonary cancer can lead to excessive ADH production. The key is to identify a situation where ADH hypersecretion is less likely to occur due to the gland's function.
Which of the following is true about the endocrine system compared to the nervous system?
- A. A single hormone can target many different responses, whereas a nerve only targets a single response.
- B. Blood can carry all the same hormones throughout the body simultaneously, producing responses all over the body; nerve cells can only target a small number of cells.
- C. Nerve cells and blood work together. The endocrine has nothing to do with the nervous system.
- D. Endocrine hormones only target a very small number of precise responses.
Correct Answer: B
Rationale: The correct answer is B because the endocrine system releases hormones into the bloodstream, allowing them to reach all parts of the body simultaneously and produce widespread responses. In contrast, the nervous system sends signals through nerve cells, which can only target a small number of specific cells. This difference in distribution and reach of signals is a key distinction between the endocrine and nervous systems.
Choice A is incorrect because a single hormone can indeed target multiple responses in different parts of the body, similar to how a nerve signal can affect multiple cells along its path.
Choice C is incorrect as nerve cells and the endocrine system can interact and influence each other's functions, such as in the case of stress response involving both systems.
Choice D is incorrect because endocrine hormones can have broad effects on various organs and tissues, not limited to a small number of precise responses.
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.