RESEARCH 102

Sympathetic and Parasympathetic System Sympathetic and Parasympathetic Nervous System In parasympathetic nervous system (PNS) acetylcholine (ACh) binds to Colinergic recerptors (can be classified further into: Muscarinic , Nicotinic): - M1-M5, Nicotinic (eg; GABA). In sympathetic nervous system (SNS) norepinephrine (NE) binds to adrenergic recerptors -  α 1 ,  α 2 ,  β 1 ,  β 2 . Abundance of the receptors: α 1  - smooth muscle cell. α 2  - inhibitory auto receptor. β 1  - Heart, Kidney. β 2 - Smooth muscle, Liver.   Binding of ACh to colinergic receptors activate PNS and deactivate SNS.  Alternatively, binding of NE  to colinergic receptors activate SNS and deactivate PNS.  In Adrenergic receptor Binding of NE to  α 1  adrenergic receptor ( G q α)  (present mostly in smooth muscles) activates Phospholipase C (PLC). PLC cleaves PIP2 (naturally attached in smooth musc...

A Short Story of GPCR GPCR stands for G-protein coupled receptor. As the name suggests, the receptor which itself is a protein is bound with another protein called G-protein. It is called G-protein because the protein has a bound GDP (Guanidine-di-phosphate). When a ligand binds to the receptor, conformational change activates the G-protein by exchanging GDP for GTP . The receptor itself is divided into 3 subunits - α, β, γ . The conformational change results into dissociation of α   subunit (bound with GTP) . The α   subunit is further divided into different types - α s , α i , α q , α 12/13a. Depending on the α   subunit type, the downstream biological signaling differs. The next section briefly talks about the signaling effects depending on the types of α subunit . G q α ( α 1 )-  Binding of ligand (eg; NE) to  α 1  adrenergic receptor ( G q α)  (present mostly in smooth muscles) activates Phospholipase C (PLC). PLC c...