Positive Feedback Mechanism

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Chapter: Anatomy, Physiology And Health Education : Homeostasis

Positive feedback is the one to which the system reacts in such a way as to increase the intensity of the change in the same direction. Positive feedback is less common than the negative feedback. However, it has its own significance particularly during emergency conditions.



Positive feedback is the one to which the system reacts in such a way as to increase the intensity of the change in the same direction. Positive feedback is less common than the negative feedback. However, it has its own significance particularly during emergency conditions.


One of the positive feedbacks occurs during the blood clotting. Blood clotting is necessary to arrest bleeding during injury and it occurs in three stages.





The Three Stages Are:


a.                    Formation of prothrombin activator

b.                    Conversion of prothrombin into thrombin

c.                    Conversion of fibrinogen into fibrin.


Thrombin formed in the second stage stimulates the formation of more prothrombin activator in addition to converting fibrinogen into fibrin (Fig. 4.4). It causes formation of more and more amount of prothrombin activator so that the blood clotting process is accelerated and blood loss is prevented quickly. Other processes where positive feedback occurs are milk ejection reflex and parturition (Fig. 4.5) and both the processes involve oxytocin secretion.


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