Hormones of Heart, Kidney, and Gastrointestinal Tract

Hormones of Heart, Kidney, and Gastrointestinal Tract

• The atrial wall of the heart secretes atrial natriuretic factor (ANF), which decreases blood pressure.
• The juxtaglomerular cells of the kidney produce erythropoietin, which stimulates erythropoiesis.
• The gastrointestinal tract secretes four major peptide hormones: gastrin, secretin, cholecystokinin (CCK), and gastric inhibitory peptide (GIP).
• Gastrin acts on the gastric glands and stimulates the secretion of hydrochloric acid and pepsinogen.
• Secretin acts on the exocrine pancreas and stimulates the secretion of water and bicarbonate ions.
• Cholecystokinin (CCK) acts on both pancreas and gall bladder and stimulates the secretion of pancreatic enzymes and bile juice.
• Gastric inhibitory peptide (GIP) inhibits gastric secretion and motility.

Mechanism of Hormone Action

• Hormones produce their effects on target tissues by binding to specific proteins called hormone receptors.
• Membrane-bound receptors are present on the cell membrane of the target cells.
• Intracellular receptors are present inside the target cell.
• Binding of a hormone to its receptor leads to the formation of a hormone-receptor complex.
• Each receptor is specific to one hormone, resulting in certain biochemical changes in the target tissue.

Physiological Functions Controlled by Hormones

• Hormones can be divided into groups based on their chemical nature: peptide, polypeptide, protein hormones; steroids; iodothyronines; and amino-acid derivatives.
• Hormones which interact with membrane-bound receptors normally do not enter the target cell, but generate second messengers which regulate cellular metabolism.
• Hormones which interact with intracellular receptors regulate gene expression or chromosome function by the interaction of the hormone-receptor complex with the genome.

Mechanism of Hormone Action (Diagram)

• A hormone (e.g., FSH) interacts with a receptor on a cell membrane, triggering a response that generates a secondary messenger.
• The secondary messenger then initiates biochemical responses, eventually leading to physiological responses like ovarian growth.

Figure 22.5

• A hormone (e.g., estrogen) binds to a hormone-receptor complex on the cell membrane, initiating a cascade of events that lead to the production of protein by binding to a genome in the nucleus.

Chemical Coordination and Integration

• Hormones provide chemical coordination, integration, and regulation in the human body.
• Hormones regulate metabolism, growth, and development of organs.
• The endocrine system is composed of several glands and organs, including the hypothalamus, pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus, and gonads (testis and ovary).
• Some organs, such as the gastrointestinal tract, kidney, and heart, also produce hormones.

This quiz covers the hormones secreted by non-endocrine glands in the heart, kidney, and gastrointestinal tract. Learn about ANF, erythropoietin, gastrin, and more!