An example of positive feedback mechanism in our body is:

ESIC Nursing Officer -2019 (Shift -1)

Applied Physiology

Easy

Appeared in: ESIC Nursing Officer -2019 (Shift -1)

Explanation

Oxytocin's role in childbirth is a classic example of a physiological positive feedback loop.
The initial stimulus is the baby's head stretching the cervix.
This stretching triggers nerve signals to the brain, which stimulates the pituitary gland to release oxytocin.
Oxytocin travels to the uterus and causes stronger contractions.
These stronger contractions push the baby's head further, which stretches the cervix more, creating an amplifying cycle.
This loop continues to intensify, leading to the birth of the baby, which ultimately stops the initial stimulus and ends the feedback loop.

Option A: Temperature regulation is a primary example of negative feedback. The body works to counteract changes in temperature to maintain a stable internal state (homeostasis).
Option B: The baroreceptor mechanism regulates blood pressure and is a classic negative feedback system. If blood pressure rises, baroreceptors signal to lower it, and if it falls, they signal to raise it, always aiming for a stable set point.
Option D: The regulation of thyroid hormone is controlled by a negative feedback loop. High levels of thyroid hormones in the blood inhibit the pituitary gland and hypothalamus from releasing TSH and TRH, thus decreasing thyroid hormone production.

Visual 1: Flowchart - The provided flowchart clearly illustrates the amplifying cycle of positive feedback in childbirth, showing how cervical stretch leads to oxytocin release, stronger contractions, and further stretch until birth.
Visual 2: Diagram - A comparative diagram showing a negative feedback loop (like a thermostat) next to a positive feedback loop (like a snowball effect) to highlight the core difference between stabilizing and amplifying systems.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiological Feedback Mechanisms: Positive vs. Negative Feedback as background academic context rather than a clinical decision trigger.
Nurses, especially in labor and delivery, must understand the positive feedback mechanism of labor. They monitor the progression of contractions and may administer synthetic oxytocin (Pitocin) to induce or augment labor, effectively 'hijacking' this natural positive feedback loop.
Recognizing when a positive feedback loop becomes pathological is critical. For example, a massive hemorrhage can trigger a vicious cycle of falling blood pressure and weakening heart function, which is a life-threatening positive feedback loop.
Most nursing interventions are aimed at supporting the body's negative feedback systems to restore homeostasis, such as administering fluids for dehydration or insulin for hyperglycemia.

How to Approach the Question

First, understand the core question: it's asking for an example of a 'positive feedback' mechanism.
Define 'positive feedback' in your mind: a process that amplifies or reinforces the initial change, moving the system further from its starting point.
Define 'negative feedback': a process that counteracts or reverses the initial change, bringing the system back to a stable set point (homeostasis).
Evaluate each option against these definitions.
Temperature, blood pressure, and hormone regulation are all about maintaining stability around a set point. These are classic negative feedback examples.
Childbirth is a process that needs to build in intensity to reach a conclusion (birth). The contractions get stronger and stronger, which fits the definition of an amplifying, positive feedback loop.

Concept Tested & Keywords

Concept Tested: Physiological Feedback Mechanisms: Positive vs. Negative Feedback
Stem keywords: positive feedback mechanism, body
Lead-in keywords: An example of

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