A lactating mother hears her baby cry and experiences milk ejection from the breasts. The neuroendocrine reflex responsible for this involves oxytocin release triggered by activation of which neuronal population?

• A Parvocellular neurons of paraventricular nucleus
• B Magnocellular neurons of supraoptic and paraventricular nuclei ✓
• C Arcuate nucleus dopamine neurons
• D Ventromedial nucleus neurons

Explanation

The milk-ejection (let-down) reflex is a neuroendocrine reflex where suckling or even auditory cues activate magnocellular oxytocin neurons in the supraoptic and paraventricular nuclei. Oxytocin is released from posterior pituitary nerve endings, causing myoepithelial cell contraction in the breast. Parvocellular neurons regulate the HPA axis, not oxytocin release.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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