During vaginal delivery, distension of the cervix triggers reflex oxytocin release from the posterior pituitary, which intensifies uterine contractions and further distends the cervix. Which feature best characterises this neuroendocrine loop?

• A Long-loop negative feedback mediated by cortisol
• B Short-loop feedback where oxytocin suppresses its own releasing factor
• C Positive feedback that is interrupted abruptly when the stimulus ends ✓
• D Ultradian oscillation independent of sensory input

Explanation

The Ferguson reflex is a classic neuroendocrine positive feedback loop: cervical stretch ascends via spinal afferents to the hypothalamus, magnocellular neurons fire bursts, and oxytocin released from posterior pituitary terminals strengthens myometrial contraction. Because it amplifies its own stimulus, it must be terminated externally, which occurs once the fetus is delivered and the cervix is no longer distended. Cortisol feedback loops belong to the HPA axis and are irrelevant here.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.