Nokea
Most of the endocrine system is regulated by:
- A. negative feedback mechanisms.
- B. positive feedback mechanisms.
- C. hormone-receptor complexes.
- D. hormone-gene complexes.
Correct Answer: A
Rationale: The correct answer is A: negative feedback mechanisms. Negative feedback mechanisms are essential in regulating hormone levels within a narrow range to maintain homeostasis. When hormone levels rise, negative feedback mechanisms signal the body to decrease production, and vice versa. Positive feedback mechanisms amplify hormone production, not regulate it. Hormone-receptor complexes and hormone-gene complexes are important for hormone actions but do not regulate the overall endocrine system.
You may also like to solve these questions
Adrenaline can be used in the following EXCEPT:
- A. Allergic reactions
- B. Acute bronchial asthma
- C. Complete heart block
- D. Angina pectoris
Correct Answer: D
Rationale: Adrenaline is a sympathomimetic drug that acts on adrenergic receptors. In acute situations like allergic reactions, bronchial asthma, and heart block, adrenaline can be beneficial due to its bronchodilator and vasoconstrictor effects. However, in angina pectoris, which is caused by reduced blood flow to the heart muscle, the vasoconstrictor effect of adrenaline can worsen the condition by increasing the workload of the heart. Therefore, adrenaline should not be used in angina pectoris.
Which of the following is not controlled by a hypothalamic-releasing hormone?
- A. ACTH
- B. ADH
- C. Growth hormone
- D. Prolactin
Correct Answer: B
Rationale: The correct answer is B: ADH. Hypothalamic-releasing hormones regulate anterior pituitary hormones. ADH is produced in the hypothalamus but stored and released by the posterior pituitary, not controlled by a hypothalamic-releasing hormone. ACTH, growth hormone, and prolactin are all controlled by hypothalamic-releasing hormones such as CRH, GHRH, and PRH, respectively.
Adonis arrives at the gym and spots a dumbbell he wants to use. When attempting to lift the weight, his biceps brachii contract, but the weight is not moved because it is too heavy. This is called?
- A. Isometric contraction
- B. Concentric contraction
- C. Eccentric contraction
- D. Incomplete tetanus
Correct Answer: a
Rationale: The correct answer is A: Isometric contraction. In isometric contraction, the muscle contracts but there is no movement at the joint. In this scenario, Adonis's biceps brachii contract but the weight is not moved, indicating an isometric contraction. In concentric contraction (B), the muscle shortens to move the weight upward. In eccentric contraction (C), the muscle lengthens while under tension, controlling the descent of the weight. Incomplete tetanus (D) refers to a state where muscle fibers are stimulated rapidly but not at the maximum rate to produce sustained contractions.
Some medications for relief of cold/allergy symptoms contain pseudoephedrine, which acts as a decongestant. If a patient who is taking an MAO inhibitor takes pseudoephedrine, what is the likely outcome?
- A. Acute bronchospasm/asthma due to ACh release from the adrenal medulla
- B. Hypertensive crisis, possible stroke
- C. Heart rate and contractile force would drop significantly and quickly
- D. The cold symptoms would quickly get worse (increased secretions)
Correct Answer: B
Rationale: Step 1: MAO inhibitors prevent the breakdown of neurotransmitters like norepinephrine.
Step 2: Pseudoephedrine stimulates the release of norepinephrine.
Step 3: The combination can lead to excessive norepinephrine, causing hypertension and potential stroke.
Therefore, the likely outcome when a patient taking an MAO inhibitor also takes pseudoephedrine is a hypertensive crisis and possible stroke (Choice B).
Summary:
- Choice A (acute bronchospasm/asthma due to ACh release from the adrenal medulla) is incorrect because pseudoephedrine does not directly cause this response.
- Choice C (heart rate and contractile force would drop significantly and quickly) is incorrect as pseudoephedrine tends to increase heart rate and blood pressure.
- Choice D (the cold symptoms would quickly get worse - increased secretions) is incorrect as pseudoephedrine is a decongestant and would not worsen cold symptoms
Which of the following does not act as a second messenger in second-messenger systems of hormone action?
- A. cyclic AMP
- B. calmodulin
- C. cyclic GMP
- D. inositol triphosphate
Correct Answer: B
Rationale: Calmodulin is not a second messenger but a calcium-binding protein that regulates various cellular processes. Cyclic AMP, cyclic GMP, and inositol triphosphate are all second messengers involved in hormone action. Calmodulin acts downstream of these second messengers to mediate their effects.