Why beta2 action is is prolonged than alpha 1&2 and beta2 action together?
The action of epinephrine is prolonged on beta-2 receptors than on alpha receptors since they are stimulated by a lower concentration than that which stimulates the alpha receptors. When the epinephrine concentration decreased (e.g. by uptake or metabolism) it will reach a level that can not stimulate the alpha receptors but still enough to stimulate the beta-2 receptors. The afferent arteriole of each glomerulus contains specialized cells, called the juxtaglomerular cells. These cells synthesize the precursor prorenin, which is cleaved into the active proteolytic enzyme renin. Active renin is then stored in and released from secretory granules.
