Which one of the following hormones is secreted by neurohypophysis that causes uterine contractions?

ESIC Nursing Officer-7July 2024

Applied Physiology

Easy

Appeared in: ESIC Nursing Officer-7July 2024

Explanation

Oxytocin is a peptide hormone secreted by the posterior pituitary gland, also known as the neurohypophysis.
It acts on specific receptors in the myometrium (uterine muscle) to increase the force and frequency of uterine contractions, which is essential for labor (parturition).
During labor, a positive feedback loop is established where cervical stretching triggers more oxytocin release, leading to stronger contractions.
Oxytocin is also responsible for the milk ejection reflex (let-down) by causing contraction of myoepithelial cells in the mammary glands.

Option A: Estrogen is primarily secreted by the ovaries and placenta, not the neurohypophysis. While it increases the uterus's sensitivity to oxytocin, it does not directly cause the powerful contractions of labor.
Option B: Progesterone is secreted by the corpus luteum and placenta. Its main role during pregnancy is to relax the uterine muscle, thus preventing premature contractions. It is often called the 'hormone of pregnancy'.
Option C: Prolactin is secreted by the anterior pituitary gland (adenohypophysis), not the neurohypophysis. Its primary function is related to lactation.

Visual 1: Diagram: The pituitary gland, showing the anterior (adenohypophysis) and posterior (neurohypophysis) lobes and the hormones they release.
Visual 2: Flowchart: The positive feedback loop of oxytocin during labor, illustrating how cervical stretch leads to oxytocin release, which in turn causes stronger uterine contractions and further cervical stretch.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiological roles of hormones secreted by the neurohypophysis (posterior pituitary) as background academic context rather than a clinical decision trigger.
A synthetic form of oxytocin (Pitocin) is one of the most common drugs used in obstetrics. Nurses administer it to induce or augment labor and to control postpartum hemorrhage by ensuring the uterus contracts firmly after delivery.
Nurses must carefully monitor patients on oxytocin for signs of uterine tachysystole (more than 5 contractions in 10 minutes), which can compromise fetal oxygen supply. If this occurs, the infusion must be stopped immediately.
What if the question asked for a hormone from the neurohypophysis that regulates water balance? The answer would be Antidiuretic Hormone (ADH), also known as vasopressin, which is the other hormone released from the posterior pituitary.

How to Approach the Question

First, break down the question. Identify the key anatomical structure: 'neurohypophysis', which is the posterior pituitary gland.
Next, identify the key physiological action required: 'causes uterine contractions'.
Recall the two hormones released from the posterior pituitary: Oxytocin and Antidiuretic Hormone (ADH).
Match the function to the hormone. Oxytocin is the hormone responsible for uterine contractions.
Evaluate the other options to confirm your answer. Estrogen and Progesterone are primarily ovarian/placental hormones. Prolactin is from the anterior pituitary. This confirms Oxytocin is the only correct choice.

Concept Tested & Keywords

Concept Tested: Physiological roles of hormones secreted by the neurohypophysis (posterior pituitary).
Stem keywords: hormones, secreted, neurohypophysis, uterine contractions
Lead-in keywords: Which one
Clinical cues: neurohypophysis points to posterior pituitary origin
Clinical cues: uterine contractions points to oxytocic action

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