Positive Feedback Loop System Used During Labor.
Homeostasis is the steady state of the body systems that living organisms maintain. Maintaining homeostasis requires that the body continuously monitors its internal conditions. From body temperature to blood pressure to levels of certain nutrients, each physiological condition has a particular set point. A set point is a value around which the normal range fluctuates. The normal range is a range of values around the set point that does not cause a reaction by the control center.
Biological systems like the body are constantly being pushed from their balance points or homeostasis. Maintenance of homeostasis usually involves negative feedback loops. Negative feedback loops act to oppose stimulus that triggers them and bring the value of the parameter that was offset back towards its set point.
Labor often begins spontaneously or may be induced medically for a variety of maternal or fetal indications. Methods of inducing labor include cervical ripening with prostaglandins, membrane stripping, amniotomy, and intravenous oxytocin (Hutchinson, 2022). During normal childbirth, there is a Positive Feedback Loop that is used. A Positive Feedback Loop intensifies a change in the body’s physiological condition or creates a stimulus, rather than reversing it or returning it to a state of homeostasis. Positive Feedback Loops are usually found in processes that need to be pushed to completion, not when homeostasis needs to be maintained.
The Positive Feedback Loop that comes into play during childbirth is the stimulation that happens when the baby’s head presses on the cervix—the bottom of the uterus, through which the baby must emerge—and activates neurons to the brain. The neurons send a signal that leads to the release of the hormone oxytocin from the pituitary gland.
Once oxytocin is released uterine contractions increase, and thus put pressure on the cervix. This causes the release of even more oxytocin and produces even stronger contractions. This positive feedback loop continues until the baby is born (Kahn Academy,2022).
According to Michael H. Walter, he stated, “To give the newborn the greatest chance of survival a series of finely tuned mechanisms have been selected for during human evolution to initiate the beginning of childbirth at the right point in time. These include the switch of uterine muscle activity from a resting state, characterized by single, unsynchronized contractions during pregnancy, to a state of coordinated uterine contractions at the point in time when the fetus is mature. In addition, the cervix must ripen and efface before it can dilate in order to allow the descent of the fetus from the uterus to the vagina “(Walter et al., 2021).
Homeostasis is regulated by Negative Feedback Loops. And much less frequently, by Positive Feedback loops. Both have the same components of a stimulus, sensor, control center, and effector. But Negative Feedback Loops are much more commonly used in the body to keep it in a state of homeostasis.
Once the baby is born, at this point, the contractions stop, and the stretching of the cervix halts which stops the release of oxytocin. This is the end of the feedback loop. The result of the stimulation, the baby pushing on the cervix causing it to stretch, was amplified by the brain stimulating the pituitary gland to release oxytocin to make birth occur more quickly by oxytocin causing the uterus to contract and push the baby out through the birth canal.
Homeostasis. (2022). Khan Academy. Retrieved July 21, 2022, from https://www.khanacademy.org/science/ap-biology/cell-communication-and-cell-cycle/feedback/a/homeostasis
Walter MH, Abele H, Plappert CF. The Role of Oxytocin and the Effect of Stress During Childbirth: Neurobiological Basics and Implications for Mother and Child. Front Endocrinol (Lausanne). 2021 Oct 27;12:742236. doi: 10.3389/fendo.2021.742236. PMID: 34777247; PMCID: PMC8578887.
Hutchison, J., Mahdy, H., & Hutchison, J. (2022). Stages of Labor. In StatPearls. StatPearls Publishing.