Nightingale Physiology Practice Test

Positive feedback loops amplify a signal until a final event ends the process. Oxytocin fits this pattern in childbirth: cervical stretch triggers oxytocin release from the posterior pituitary, which increases uterine contractions; those contractions cause more cervical stretch, leading to even more oxytocin release and stronger contractions until delivery occurs. A similar reinforcing effect happens during milk ejection, where suckling promotes oxytocin release to push out milk as long as feeding continues. The other hormones don’t form this kind of self-amplifying loop: prolactin is primarily regulated by dopamine and other factors rather than a self-reinforcing cycle; ADH is governed by osmolality with negative feedback to restore balance; melatonin is driven by light-dark cues and circadian signals, not a positive feedback loop.