Which of the following drugs selectively stimulates β2 adrenoceptors:

Correct Answer: D

Rationale: The correct answer is D: Salbutamol. Salbutamol is a selective β2 adrenoceptor agonist. It has a higher affinity for β2 receptors compared to β1 receptors, leading to bronchodilation without significant effects on the heart. A: Adrenaline and C: Isoprenaline stimulate both β1 and β2 receptors, causing increased heart rate and bronchodilation. B: Noradrenaline stimulates α1, α2, and β1 receptors, leading to vasoconstriction and increased heart rate. Therefore, salbutamol is the only drug that selectively stimulates β2 adrenoceptors, making it the correct choice.

Correct Answer: C

Rationale: Adrenaline, also known as epinephrine, is a hormone that activates the fight-or-flight response. It causes bronchial muscle relaxation (A), increases cardiac contractility (B), and increases sweat secretion (D) to prepare the body for action. However, adrenaline inhibits intestinal motility (C) to conserve energy for vital functions during stressful situations. Therefore, the correct answer is C because adrenaline does not increase intestinal motility. Relaxation of bronchial muscle, increased cardiac contractility, and increased sweat secretion are all effects of adrenaline, making choices A, B, and D incorrect, respectively.

Correct Answer: C

Rationale: Rationale: - Noradrenaline stimulates both α and β receptors, leading to increased heart rate and vasoconstriction. - It does not decrease heart rate; it actually increases heart rate due to its actions on β receptors. - Noradrenaline causes vasoconstriction by activating α receptors, leading to increased blood pressure. - The incorrect statement is C, as noradrenaline actually increases blood pressure by causing vasoconstriction.

Correct Answer: D

Rationale: Step 1: Atropine is an anticholinergic drug that blocks muscarinic receptors. Step 2: Blocking muscarinic receptors in the eye leads to dilation of the pupil, known as mydriasis. Step 3: Therefore, the correct answer is D, as atropine indeed produces mydriasis. Summary: A is incorrect because atropine is not a neuromuscular blocker. B is incorrect as atropine actually induces tachycardia. C is incorrect as atropine inhibits GIT motility and secretion.

Correct Answer: B

Rationale: The correct answer is B: Terbutaline. Terbutaline is a beta-2 adrenergic agonist used as a bronchodilator. It can stimulate beta-2 receptors in skeletal muscle, leading to muscle tremors as a common side effect. Ipratropium (A) is an anticholinergic bronchodilator and typically does not cause muscle tremors. Atenolol (C) is a beta-blocker and is not associated with muscle tremors. Nicotinic acid (D) is used to treat dyslipidemia and does not commonly cause muscle tremors. Therefore, Terbutaline is the most likely drug to cause muscle tremor among the options provided.