<prompt> Positive feed back is seen in AE :LH SurgeEntry of Ca into sarcoplasmic reticulumStimulation of gastric secretion of histamine gastrinThrombolytic activity in coagulation cascade  <response>: C i.e. Stimulation of gastric secretion by histamine gastrinMost control system of the body are negative feed back system. Release of acid in stomach by the action of gastrin is negative feed back system, as Tin acid secretion inhibits fuher gastrin secretion. 