Question

Which of the following hormones are released in maximum amount during Ferguson's reflex at parturition?

• A. Estrogen
• B. Progesterone
• C. Oxytocin
• D. Thyroxin

Hint:

Ferguson's reflex is a classic example of a positive feedback loop in animal physiology:
Vaginal stretch \(\rightarrow\) Hypothalamus \(\rightarrow\) Posterior Pituitary releases Oxytocin \(\rightarrow\) Stronger uterine contractions \(\rightarrow\) More stretch.
This cycle only stops once parturition is complete.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Ferguson's reflex (also known as the maternal stretching reflex) is a neuroendocrine reflex that facilitates the expulsion of the fetus during the second stage of parturition.
It involves a positive feedback loop between mechanical stimulation of the birth canal and endocrine secretion from the brain.

Step 2: Detailed Explanation:
Let us analyze the physiological steps of Ferguson's reflex:
1. Mechanical Stimulus: During the second stage of labor, the fetus enters the cervix and vagina.
The physical pressure and stretching of the cervix and vaginal wall stimulate local sensory mechanoreceptors (stretch receptors).
2. Neural Pathway: These receptors send sensory nerve impulses up the spinal cord to the paraventricular and supraoptic nuclei of the hypothalamus in the brain.
3. Endocrine Release: In response to these impulses, the posterior pituitary gland is stimulated to release large amounts of oxytocin into the bloodstream.
4. Target Action: Oxytocin travels via the blood to the uterus, where it binds to highly upregulated oxytocin receptors on the myometrium (uterine smooth muscle).
This binding triggers powerful, coordinated uterine contractions, pushing the fetus further into the birth canal.
This further stretching of the cervix stimulates more oxytocin release, creating a positive feedback loop that continues until the fetus is successfully expelled.
Other hormones, such as estrogen and progesterone, are important for preparing the uterus for labor, but they are not the active hormones released during this neuroendocrine reflex.
Therefore, Oxytocin is the primary hormone released during Ferguson's reflex.

Step 3: Final Answer:
The correct option is (C).