Explain the hormones of (i) Heart, (ii) Kidney and (iii) GI Tract

The Hormones of the Heart, Kidney and Gastrointestinal Tract:
(i) Heart/Atrium: Atrial wall of human heart produces important peptide hormone called atrial natriuretic factor (ANF). ANF reduces blood pressure. When the blood pressure is enhanced, some special cells secrete ANF, that produces vasodilatory actions on the blood pressure. The blood vessels are dilated and blood pressure declines as a result.
(ii) Kidney : Juxtaglomerular cells of kidney secrete a peptide hormone called erythropoietin. It stimulates erythropoiesis or formation of RBCs of blood.
(iii) GI Tract : The endocrine cells found in various
parts of gastro-intestinal tract (GI Tract) secrete four peptide hormones : gastrin, secretin,
cholecystokinin (CCK) as well as gastric inhibitory peptide or GIP.
(a) Gastrin : It acts on gastric glands. It stimulates secretion of hydrochloric acid (HC1) and pepsinogen.
(b) Secretin : It acts in islets of Langerhans/ exocrine pancreas. It stimulates secretion of water and bicarbonate ions.
© CCK : It acts on both pancreas and gall bladder. It stimulates the secretion of pancreatic enzymes and bile juice, respectively.
(d) GIP : It suppresses gastric secretion and motility