18/06/2025
The , which mainly involves a neurohormonal reflex called the milk let-down reflex (or milk ejection reflex).
1️⃣ Stimulation Phase (Suckling Reflex)
• When the infant latches onto the breast and begins suckling, mechanoreceptors (touch receptors) located in the ni**le and ar**la are activated.
• These receptors detect the physical stimulation from the baby’s mouth and tongue movements.
⸻
2️⃣ Afferent Neural Pathway (Signal to Brain)
• Nerve impulses travel via spinal nerves (thoracic spinal cord, T4-T6 level) up to the brain.
• The impulses reach the hypothalamus, a key regulatory center for many hormonal functions.
⸻
3️⃣ Hypothalamic Activation
• The hypothalamus responds by:
• Stimulating the posterior pituitary gland (neurohypophysis) to release oxytocin.
• Stimulating the anterior pituitary gland (though not shown in the image) to release prolactin, which is responsible for milk production.
⸻
4️⃣ Hormonal Response
A. Oxytocin
• Oxytocin is released into the bloodstream from the posterior pituitary.
• It reaches the breast and binds to oxytocin receptors located on the myoepithelial cells surrounding the alveoli (milk glands).
• This causes these smooth muscle cells to contract and squeeze milk into the milk ducts → milk moves toward the ni**le.
B. Prolactin (not shown in image but very important)
• Prolactin is released by the anterior pituitary.
• It stimulates the alveolar epithelial cells (lactocytes) to synthesize and secrete milk components (lactose, lipids, proteins).
• Prolactin works primarily in between feeds, to replenish milk for future feeds.
⸻
5️⃣ Ejection of Milk (Milk Let-Down Reflex)
• The baby receives milk as it is ejected through the ni**le.
• The continuous suckling maintains this neurohormonal loop.
⸻
6️⃣ Feedback Mechanism (Positive Feedback Loop)
• The more the baby suckles:
• The more nerve impulses sent → more oxytocin and prolactin released → more milk produced and ejected.
• This positive feedback continues until suckling stops.
⸻
7️⃣ Emotional & Psychological Inputs
• The hypothalamus can also be influenced by:
• Hearing baby’s cry
• Thinking about the baby
• Stress (can inhibit oxytocin release)
• Relaxation (can promote oxytocin release)
