Damaged tissue releases chemicals that activate platelets and stimulate the formation of blood clots. Which of the following predictions about the activity of platelets best describes a positive feedback mechanism?

A. Activated platelets release chemicals that inhibit blood clot formation.
B. Activated platelets release signaling molecules that inhibit cell division in damaged tissue.
C. Activated platelets constrict the blood vessels, stopping blood flow.
D. Activated platelets release chemicals that activate more platelets.

When a stimulus or a change in some condition triggers a response that intensifies the changing condition, the mechanism is called a positive feedback mechanism.

Any damage to tissues makes the platelets to contact and stick to parts such as collagen fibers of the connective tissue present under the damaged endothelial cells. This process of platelet adhesion activates the platelets and brings about changes in them. The activated platelets grow many projections to contact and interact with one another. They also release ADP and thromboxane A2 which in turn activates the nearby platelets. The ADP makes other platelets in the area sticky. The stickiness of the newly recruited and activated platelets causes them to join the originally activated platelets. Eventually, the accumulation and attachment of large numbers of platelets form a platelet plug.

Here, release of chemicals from the activated platlets to activate more platlets represents the positive feedback mechanism.

aliasger2709 aliasger2709 · Answer 2 · 2021-11-16T07:36:29+01:00

Thrombocytes commonly known as platelets are the small, colorless cell particles that are present in the blood system and is an important blood-clotting element. They are synthesized inside the bone marrow of organisms from the stem cells.

The correct answer is :

Option D. Activated platelets release chemicals that activate more platelets.

A positive feedback mechanism ensures the controlling of self continuation events that can become uncontrollable.

When in the case of injury the damaged tissue release chemicals which activate platelets and stimulate the formation of a blood clot.

The platelets attach with collagen present in the connective tissues of the damaged tissues and activate certain chemical reactions.

When the platelet gets activated it releases several important cytokines and chemical mediums.

Some of the chemicals it releases are Platelet growth factor, vascular endothelial growth factor, coagulation chemicals, serotonin and many more.

The larger accumulation of platelet leads to the formation of the clot.

Therefore, activated platelets release chemicals that activate more platelets.

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