Platelets, which have negatively charged cell membranes, adhere to the positively charged surface of a torn blood vessel. As they do so, they release substances that attract more platelets to the damaged area and change the charge on their cell membranes to positive. More platelets adhere to the damaged area. The cycle repeats until the damaged area is sealed. What sort of feedback loop is formed, and why?
A)This is a positive-feedback loop because the response reinforces the initial change.
B)This is a negative-feedback loop because the response opposes the initial stimulus.
C) This is a negative-feedback loop because having too many platelets in one area blocks blood flow.
D) This is a positive-feedback loop because the response prevents a person from haemorrhaging to death.

Question

Quizplus · Accepted Answer

This is a positive-feedback loop because the response reinforces the initial change. As platelets adhere to the damaged area and release substances that attract more platelets, the positive charge on their cell membranes increases, leading to more platelets adhering and releasing more substances, which attracts even more platelets. This cycle continues until the damaged area is sealed. The response of attracting more platelets reinforces the initial change of platelets adhering to the damaged area.

Platelets, Which Have Negatively Charged Cell Membranes, Adhere to the Positively