Welcome all to IS PHARMACOLOGY DIFFICULT Podcast ! I am Dr Radhika Vijay. In today's episode, I will talk about the Two state receptor model, on the basis of which we can alternatively describe, Agonist, Competitive antagonist , Partial agonist and Inverse agonist. The receptor is believed to exist in two interchangeable states, Ra(active state ), Ri(inactive state). Both stay in equilibrium. Ri state is favored at equilibrium. Agonist(A) binds preferentially to Ra, equilibrium shifts, a certain response is produced. A competitive antagonist(B)  binds equally to Ra and Ri, no response is produced, it does not alter the equilibrium.A partial agonist (C) binds to few receptor sites on Ra, produces a submaximal response, the equilibrium shifts to Ra a little only, an inverse agonist (D), has more inclination towards Ri, an opposite response is produced, In resting state, equilibrium shifts towards Ra. Certain receptors like AT1, Beta adrenergic, etc exhibit constitutive activation. Apart from two receptor model, receptors can adopt multiple active inactive conformations, favored by different ligands. This was all for the Wellness green symbolic Wednesday, after all these descriptions, I will call it for the day, till next episode, do follow me here, stay tuned, do rate and review on ITunes, Apple podcasts, hope all have a safe, ecofriendly day, thank you!!