Cholinergic and Adrenergic receptors Flashcards
What are Adrenergic receptors
Receptors that are activated by catecholamines
Name the different types of Adrenergic receptors and their associated G proteins
The 5 types are Alpha 1 which binds to Gq, Alpha 2 which binds to Gi, Beta 1, Beta 2 and 3 which all bind to Gs G protein.
Noradrenaline binds to alpha 1 and 2 as well as beta 1. Adrenaline binds to all 5 of the receptors
Detail the mechanism of alpha receptor 1
When alpha 1 binds to a catecholamine, it activates its G protein which activates phospholipase C, an enzyme that cleaves PIP2 in to IP3 and DAG
IP 3 binds to the endoplasmic reticulum causing its calcium ion channels to open allowing Ca to flow into the cytoplasm causing cell potential to increase
Dag binds to PROTEIN KINASE C, and when the calcium levels increase, it becomes fully activated and goes to phosphorylate other proteins, leading to a cell response depending on the location
Detail the mechanism of Beta receptors
When the Gs protein on all the Beta receptors are activated, they activate adenylate cyclase which removes 2 P groups from ATP turning it into cAMP, which then goes on to bind to protein Kinase A and causes it to dissociate from its regulatory section and allows the catalytic subunit to phosphorylate other proteins leading to a cellular response
Detail the mechanism of alpha receptor 2
When Gi protein on Alpha 2 receptor is activated, it binds to adenylate cyclase and inhibits it, causing a negative feed back loop on Gs proteins effects, this leads to inactivation of cells that are less important during flight or fight response.
What are Cholinergic receptors?
Receptors that are activated when they bind to acetyl choline
How many types of cholinergic receptors are there? Name them
There are two types. Nicotinic and muscarinic
Explain the difference between preganglionic neurons and post ganglionic neurons in the sympathetic and parasympathetic nervous system.
In the SYMPATHETIC nervous system, preganglionic neurons release acetylcholine which binds to Nicotinic receptors on post ganglionic neurons.’
Postganglionic neurons release neurotransmitters ADRENALINE AND NOR ADRENALINE which bind to adrenergic receptors on the plasma membrane of target organs
in PARASYMPATHETIC both pre and post ganglionic neurons release acetylcholine from pre ganglionic to post ganglionic. Post ganglionic release acetylcholine which binds to muscarinic receptors on the target organ
What are nicotinic receptors and what are they composed of?
Nicotinic receptors (aka ionotropic acetylcholine receptors) are ligand gated ion channels, meaning when acetylcholine binds to them, they open to allow sodium and potassium ions to flow through them They are composed of 5 subunits 2 alpha 1 beta 1 gamma 1 sigma
What happens when the nicotinic bind to acetyl choline
When acetyl choline binds to it, the tunnel opens allowing for Sodium to flow in and potassium to flow out. The cell is depolarized and becomes more positive triggering a cellular response
What are Muscarinic receptors and what are they composed of?
Muscarinic receptors (aka metabotropic acetylcholine receptors) activate intracellular proteins when binded to acetylcholine. They are a type of G protein coupled receptor and their g proteins are made up of alpha, gamma and beta subunits.
