Question

Summarize the sources, stimulus for, and effects of these hormones: atrial naturetic factor, angiotensin II, antidiuretic hormone.

Answer 1

Atrial Naturetic factor

Thispeptide hormone (ANP//ANF)  hormone is released in case of an elevated blood pressure or the blood volume.

Source: ANF is produced by the right atrial wall of the heart when the right atrium is stretched enormously by the huge amount of the blood filled in by increased blood pressure. (from superior vena cava and inferior vena cava)

Stimulus : High blood volume in the right atrium triggering the artery wall

Function:

1. Reduce blood pressure by going and binding in the receptors of the arteries on the skeletal & smooth muscles and causing vasodilation.
2. Reduces blood pressure by decreasing blood volume by increasing the urine output, by acting on kidneys. More water is released through the urine out of the body by inhibiting the water reabsorption from the renal tubules.

Angiotensin ii

It is a steroid hormone that causes the vasoconstriction and increases the blood pressure.

Source: Adrenal gland, Kidney produces Renin which convert inactive angiotensinogen (produced by liver) into angiotensin I, CONVERT THE ANGIOTENSIN I TO ANGIOTENSIN.II by the action of ACE (Angiotensin Converting Enzyme produced in lungs). Angiotensin II act on adrenal gland to release the Aldosterone.

Stimulus; Low fluid volume moving through nephrons

Function: Act on the collecting duct in kidney: Sodium reabsorption, Water retention from renal tubules.

AntiDiuretic Hormone(ADH)/Vasopressin

Source:Supra optic nucleus of the hypothalamus which comes down to the pituitary gland. (act as a store house)

Stimulus: Hyperosmolar blood and extra cellular fluid.(Normal level : 290-300 mOs m/l).Anterolateral area of third ventricle has some osmoreceptors which detect the blood osmolarity, which stimulate the hypothalamus to release the ADH.

Function: In low concentration, it act as Antidiuretic,Water reabsorption from the kidney. In high concentration act as a vasoconstrictor. The DCT and collecting duct luminal fluid is highly diluted with water.Cells of this part of nephron has ADH receptors mainly 7-pass receptor. ADH bind with these receptors and stimulate intercellular G protein. Intercellular G protein stimulate adenylyl cyclase,which convert ATP into cyclic AMP. Cyclic AMP goes up, it will phosphorilyse protein kinase A. All these process is to activate this enzyme.

The cells of this part of nephorn have some vesicles inside having "aquaporins".Protein kinase A  bind with aquaporin channels. In the presence of ADH, aquaporin channels are binded on the luminal side of the nephron.So ADH makes this cells water permeable. The interstitial fluid is hyposmolar and the luminal fluid is hyperosmolar, and the water will be reabsorbed to the cell by osmosis.