**Question:** Oxytocin will not do the following action

A. Increase heart rate
B. Promote vomiting
C. Stimulate bronchodilation
D. Inhibit uterine contractions

**Core Concept:**
Oxytocin is a hormone and neurotransmitter produced by the posterior pituitary gland. It plays a crucial role in several physiological processes, particularly in the areas of parturition (childbirth), lactation, and social bonding. Oxytocin receptors are present in various tissues, including the uterus, lungs, and cardiovascular system.

**Why the Correct Answer is Right:**
Oxytocin is primarily associated with uterine contractions during childbirth and breastfeeding. In the context of this question, we are focusing on its effects on the cardiovascular system. Oxytocin's primary action on the heart is to increase its contractility and heart rate. However, the question highlights that oxytocin will not do **A** (increase heart rate).

**Why Each Wrong Option is Incorrect:**
- **Option A (Increase heart rate):** Oxytocin does increase heart rate, contradicting the statement made in the question. This option is incorrect because oxytocin, rather than inhibiting heart rate, actually increases it.
- **Option B (Promote vomiting):** While oxytocin is not directly associated with inducing vomiting, the question does not focus on its direct effects on the gastrointestinal tract. This option is incorrect as it does not relate to the primary action of oxytocin.
- **Option C (Stimulate bronchodilation):** Oxytocin does not primarily affect the lungs or bronchial tubes. This option is incorrect because oxytocin's primary action is on the cardiovascular system, not the respiratory system.
- **Option D (Inhibit uterine contractions):** Oxytocin is known for its role in stimulating uterine contractions during childbirth, making this option incorrect. Oxytocin's primary action is to increase uterine contractility, not inhibit it.

**Clinical Pearl:**
Oxytocin's role in childbirth is essential for understanding its physiological effects. Adequate knowledge of oxytocin is crucial for healthcare professionals, as it aids in managing complications related to oxytocin and its effects. In summary, oxytocin mainly acts on the cardiovascular system and uterus, but does not directly affect the heart rate or bronchial tubes.