Final answer:
Childbirth in humans involves a positive feedback loop where the baby's pressure on the cervix triggers the release of oxytocin from the pituitary gland, leading to stronger uterine contractions, pushing the baby further and causing greater cervical stretching, continuing until birth.
Step-by-step explanation:
Positive Feedback Loop During Childbirth
The process of childbirth in humans is a classic example of a positive feedback loop, which is an essential mechanism for the proper delivery of babies. When a baby pushes against the cervix during labor, it triggers stretch-sensitive nerve cells to send signals to the brain. In response, the brain stimulates the pituitary gland to release the hormone oxytocin into the bloodstream, causing uterine contractions to become stronger, pushing the baby further down the birth canal. This leads to even more significant stretching of the cervix, which sends a stronger signal to release more oxytocin, thereby increasing the intensity of contractions.
This cycle continues until the baby is born, which then ends the stretching of the cervix and the release of oxytocin, halting the contractions. Oxytocin also facilitates the 'let-down' reflex for milk ejection after birth, stimulated by an infant's suckling.
It's important to correct a common misconception; the oxytocin is released from the pituitary gland, not the parathyroid gland as occasionally mistaken. The parathyroid gland is involved in calcium homeostasis, not childbirth.