Which of the following scenarios can be classified as a negative feedback loop? a increase in blood pressure to reduce heart rate
b increase in testosterone to help increase a fight-or-flight response
c increase in oxytocin caused by increased contractions
d increase in platelet production to help increase blood clotting

The scenario that can be considered an example of a negative feedback loop is increase in platelet production to help increase blood clotting (option d).

Explanation:

Negative feedback loop is what occurs when a change occurs in the body, producing a response that decreases or stops that change, with the intention of maintaining homeostasis.

When there is a wound that produces bleeding, a series of mechanisms are activated, the coagulation cascade, which promotes the release of factors that allow the formation of clots. The increased release of platelets implies negative feedback because it helps to stop the change that occurs in the body, the loss of blood, through the formation of clots.

One thing that can cause confusion is the fact that this response also involves positive, though limited, feedback that promotes the production of clotting factors and platelets to increase clot formation. What really happens is that the positive feedback promotes the general feedback, which is the negative feedback: clot formation to stop the bleeding, restoring homeostasis.

The other options are not correct because:

    a. Increase in blood pressure to reduce heart rate is not possible.

    b. In the fight and flight response the hormones involved are cortisol and adrenaline, not testosterone.

    c. Increased oxytocin in response to uterine contractions is positive feedback.