What mechanism controls the release of oxytocin by the posterior pituitary?

The release of oxytocin by the posterior pituitary is primarily controlled by a neurohormonal reflex. This mechanism involves the direct stimulation of neurosecretory cells in the hypothalamus, which produce oxytocin. When certain stimuli occur, such as the stretching of the cervix during labor or suckling by an infant, these neurosecretory cells send action potentials down their axons to the posterior pituitary, prompting the release of oxytocin into the bloodstream.

This neurohormonal reflex is critical for various physiological processes, particularly in childbirth and lactation. In labor, oxytocin enhances uterine contractions, facilitating delivery, while during breastfeeding, it promotes milk ejection in response to an infant's suckling.

While hormonal stimulation, positive feedback, and negative feedback are also important concepts in endocrine regulation, they do not primarily describe the immediate mechanism by which oxytocin is released. Hormonal stimulation usually refers to other hormones triggering the release of different hormones, and feedback mechanisms describe how levels of a hormone regulate their own production, which is not how oxytocin is directly released in response to immediate physiological cues.