The hormone that stimulates uterine contractions is

Correct Answer: A

Rationale: Step-by-step rationale for why A (oxytocin) is the correct answer: 1. Oxytocin is known as the "love hormone" and is primarily responsible for stimulating uterine contractions during labor. 2. It is produced by the hypothalamus and released by the pituitary gland. 3. Oxytocin plays a crucial role in childbirth, breastfeeding, and bonding between mother and child. Summary: B: Estrogen is a female sex hormone that regulates the menstrual cycle and development of female secondary sexual characteristics. C: Granular cell carcinoma is a type of cancer that does not have any relation to uterine contractions. D: Progesterone is another female sex hormone that helps maintain pregnancy and prepare the body for childbirth, but it does not directly stimulate uterine contractions like oxytocin does.

Correct Answer: B

Rationale: The correct answer is B: D2. Atypical antipsychotics primarily target dopamine D2 receptors, reducing dopamine activity. This helps alleviate symptoms of psychosis with fewer extrapyramidal side effects compared to typical antipsychotics that target D1 receptors. Choice A: D1 receptors are not the primary target for atypical antipsychotics. Choice C: D3 receptors are not the main target, although some atypical antipsychotics may have activity at D3 receptors. Choice D: D4 receptors are not the main target for atypical antipsychotics.

Correct Answer: A

Rationale: The correct answer is A because buprenorphine is a partial agonist at the Mu receptor. This means it can activate the receptor but with less efficacy compared to a full agonist, resulting in a ceiling effect and lower risk of respiratory depression. Choice B is incorrect because buprenorphine is not a full agonist at the Mu receptor. Choices C and D are incorrect as buprenorphine primarily acts on the Mu receptor, not the K receptor.

Correct Answer: C

Rationale: The correct answer is C: LTC4. Slow reacting substance of anaphylaxis (SRS-A) is a leukotriene, with LTC4 being the initial form. It plays a key role in allergic reactions by causing bronchoconstriction and increased vascular permeability. PGD2, TXA2, and PGI are not classified as slow reacting substances of anaphylaxis and do not have the same physiological effects as LTC4.

Correct Answer: A

Rationale: Bradykinin is a peptide that causes vasodilation, pain, and an increase in vascular permeability. However, it does not directly cause bronchodilation. This is because bradykinin primarily acts on blood vessels and capillaries, leading to increased blood flow and leakage of fluids, but it does not have a direct effect on the smooth muscle of the bronchioles. Therefore, the correct answer is A. Vasodilation, not bronchodilation. Choices B, C, and D are incorrect because they are all known actions of bradykinin based on its physiological effects.