Which of the following illustrates a positive feedback mechanism?
A.
Body temperature control.
B.
Control of blood sugar.
C.
Uterine contractions during childbirth.
D.
Maintaining blood pressure.
The Correct Answer and Explanation is:
The correct answer is:
C. Uterine contractions during childbirth.
Explanation:
A positive feedback mechanism is a process that amplifies or increases the effects of a stimulus, leading to a greater change in the same direction. This type of feedback loops contrasts with negative feedback mechanisms, which work to counteract or diminish the effects of a stimulus to maintain homeostasis.
Uterine contractions during childbirth are a classic example of positive feedback. During labor, the hormone oxytocin is released, which stimulates uterine contractions. As contractions become more frequent and intense, the pressure on the cervix increases. This pressure is detected by stretch receptors, which signal the brain to release more oxytocin. The increased oxytocin levels further intensify contractions, which in turn increases cervical pressure even more. This feedback loop continues to amplify until childbirth occurs, resulting in the delivery of the baby. The cycle continues until the stimulus (childbirth) is complete, demonstrating a clear positive feedback loop that reinforces the process rather than opposing it.
Body temperature control (A), control of blood sugar (B), and maintaining blood pressure (D) are examples of negative feedback mechanisms. In these cases, the body detects deviations from a set point and activates processes to return to the normal range:
- Body temperature control involves mechanisms such as sweating or shivering to restore normal body temperature when it deviates from the set point.
- Control of blood sugar involves insulin and glucagon to lower or raise blood sugar levels, respectively, returning blood glucose to its normal range.
- Maintaining blood pressure involves adjustments in heart rate and blood vessel diameter to keep blood pressure within a healthy range.
In these negative feedback mechanisms, the response acts to counterbalance the initial change, thus stabilizing the system and maintaining homeostasis, unlike positive feedback mechanisms which escalate the process until a specific event is achieved.