Anatomy & Physiology of Lactation Flashcards
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Which nerve pathway carries sensory signals from nipple stimulation to the hypothalamus to trigger oxytocin release?
Answer: Thoracic spinal nerves T3–T5 via the spinothalamic tract
Sensory signals from nipple mechanoreceptors travel via intercostal branches of thoracic spinal nerves T3–T5 to the hypothalamus, stimulating oxytocin release.
Stress and pain can inhibit the milk ejection reflex primarily by elevating which hormone?
Answer: Epinephrine (adrenaline)
Elevated epinephrine from stress causes vasoconstriction of mammary blood vessels, reducing oxytocin delivery to myoepithelial cells and inhibiting let-down.
A mother notices milk dripping from the opposite breast while nursing on one side. Which physiological event causes this?
Answer: Bilateral systemic oxytocin release triggering both breasts simultaneously
Oxytocin released into the bloodstream acts systemically, triggering myoepithelial contraction in both breasts simultaneously, causing milk to leak from the non-nursing breast.
What is the primary mechanism by which frequent nursing maintains high prolactin levels?
Answer: Nipple stimulation suppresses hypothalamic dopamine, allowing prolactin to rise
Suckling stimulates afferent nerve signals that suppress hypothalamic dopamine (PIF) release, removing inhibition and allowing prolactin surges with each feeding.
At what time of day are prolactin levels typically highest, and what is the clinical implication?
Answer: Early morning; nighttime and early morning feeds are most effective for maintaining supply
Prolactin follows a circadian rhythm with peaks during sleep and early morning, making nighttime and early morning nursing sessions particularly effective for sustaining milk supply.
Which receptor type on lactocytes (milk-secreting cells) must be activated for prolactin to stimulate milk synthesis?
Answer: Transmembrane prolactin receptor (JAK2-STAT5 pathway)
Prolactin binds to a transmembrane receptor that activates the JAK2-STAT5 signaling pathway, which translocates to the nucleus and upregulates milk protein gene expression.
The milk ejection reflex can be conditioned to occur in response to a baby's cry. This conditioning occurs because:
Answer: Repeated pairing of the cry with actual nursing creates a learned oxytocin trigger
Pavlovian conditioning allows neutral stimuli (cry, smell, thought of baby) repeatedly paired with nursing to independently trigger oxytocin release and let-down.