Which of the following is not an action of oxytocin?

Appeared in: SGPGI Nursing Officer-2022

Explanation

Lactogenesis refers to the synthesis or production of milk within the alveolar cells of the breast.
This process is primarily stimulated by the hormone prolactin, which is secreted by the anterior pituitary gland.
Oxytocin, secreted by the posterior pituitary, does not produce milk; its role is to eject the milk that prolactin has helped produce.
Therefore, lactogenesis is not an action of oxytocin.

Option B: This is a primary and well-known function of oxytocin. It stimulates the smooth muscle of the uterus to contract, which is essential for labor, delivery, and postpartum uterine involution.
Option C: This is the specific cellular mechanism by which oxytocin causes milk ejection. It binds to receptors on myoepithelial cells surrounding the breast alveoli, causing them to contract.
Option D: Milk ejection, also known as the let-down reflex, is the direct result of oxytocin causing myoepithelial cells to contract. This is a key function of oxytocin in lactation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of lactation and uterine function, specifically the distinct roles of oxytocin and prolactin as background academic context rather than a clinical decision trigger.
Nurses frequently administer synthetic oxytocin (Pitocin) to induce or augment labor and to control postpartum hemorrhage.
When administering oxytocin, it is critical to monitor uterine activity for tachysystole (more than 5 contractions in 10 minutes), which can compromise fetal oxygenation. The infusion must be stopped if this occurs.
Another key nursing intervention is monitoring for water intoxication, a rare but serious side effect of high-dose oxytocin, as it has an antidiuretic effect similar to ADH. Signs include headache, confusion, and nausea.

How to Approach the Question

First, identify the negative framing of the question by spotting the word 'not'. This means you are looking for the option that is the exception.
Next, recall the key hormones involved in lactation: prolactin and oxytocin.
Create a mental mnemonic to differentiate their primary roles: Prolactin is for milk Production; Oxytocin is for milk 'Outflow' or ejection.
Evaluate each option against this rule:
Does oxytocin cause uterine contraction? Yes.
Does oxytocin cause myoepithelial cell contraction? Yes, this is how it ejects milk.

Concept Tested & Keywords

Concept Tested: Hormonal regulation of lactation and uterine function, specifically the distinct roles of oxytocin and prolactin.
Stem keywords: oxytocin, action
Lead-in keywords: not
Negative lead-in flag: The question asks to identify the option that is NOT an action of oxytocin.

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E6 Physiology Ganong 27e Vol 1 Part 2 p. 92-94

E6 Gynecology Williams p. 365-430

E6 Physiology Essentials Sembulingam 10e Part 2 p. 30-32

Practise the full SGPGI Nursing Officer-2022

Attempt every question from this paper in a timed mock, then review the full solution for each one.