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24 Cards in this Set

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  • Back
What is a primary messenger?
Signal that functions to disseminate information to cells
What are the various types of receptors?
Ligand-gated ion channels
G-protein coupled
Enzyme Receptors
Nuclear Receptors
What is a transducer?
Usually a transmembrane protein that is activated by the receptro and relays the signal of the primary messenger
What is an effector
Serves to amplicfy the signal given by the transducer;
What is a second messenger?
Generated by an activated effector; a key component of the amplification process
what type of receptors are nicotinic receptors?
They are acetylcholine ion channel receptors. Because they are channels and not enzymes they act rapidly
How many Ach molecules does it require to activate Nn or Nm receptors?
Both require two Ach molecules
Nn - being neuronal made of heteropentamer of 2 alphas and 3 betas or a homopentamer of 5 alpha subunits
Nm being Neuromuscular Junction receptors of a pentamer being 2 alpha, 1 beta, 1 gamma, and 1 delta
How many known muscarinic receptors are there and how many are clinically significant and what type of receptors are they?
There are 5 known with 3 clinically significant
THey are G-protein coupled receptors that bind Ach. Because they are G-protein their responses are slower
The G-protein coupled receptor is made of?
trimeric proteinalpha, beta, and gama subunits
What are the characteristics of an M1 receptor?
It is a Gq coupled receptor. Gq referring to the alpha subunit isoform. The effector is PLC which causs and increase in intracellular Ca2+. Along with PLC activation the product DAG also causes PKC activation.
M1 is involved in the depolarization of ANS and CNS, and the production of Acid
What are the characteristics of M2 receptors?
They are coupled to Gi proteins causing a down regulation of Adenylate cyclase inhibiting intracellular cAMP. Ultimately this decreases intracellular Ca2+ decreasing cardiac muscle contractility. It may also be coupled to a potassium ion channel leading to hyperpolarization inhibiting the heart depolarization. Ach also causes NO production to relax muscls
What are the characteristics of M3 receptors?
Gq coupled like M1. SLUD effects.
Salivation, Lacrimation, Urination, Defecation
Generation of IP3 and increased Ca2+ causing Bronchial, sweat, and salivary secretions
Acts on endothelium where it increases NO causing relaxation of vasculature.
Where is the alpha 2 receptor located at the postsynaptic neuron junction?
On the presynaptic membrane as a feedback inhibitor of NE release
Adrenergic receptors are what type of receptors?
G protein coupled
What are the characteristics of the alpha 1 receptor?
Alpha 1a, 1b, and 1d are subtypes.
It is a Gq protein that similar to other Gqs (M1 and M3) will activate PLC causing IP3 and DAG production ultimately leading to an increased in Ca2+
Characterize the Alpha 2 receptor.
Subtypes Alpha2a, Alpha2b, alpha2c.
A presynaptic Gi/o inhibitor receptor. Utilizes NE. It is aka autoreceptor (transformers... more than meets the eye) Inhibits AC which decreases cAMP levels.
What effects does binding the Alpha 2 receptor have?
Decreases insulin secretion, causes aggregation of platelets, causes presynaptic inhibition of NE, and relaxes inestinal smooth muscle. It is also coupled to a potassium channel which causes hyperpolarization
All the Beta receptors are what type?
Gs protein receptors. meaning that they activate Adenylate Cyclase and increase cAMP levels.
Characterize the Beta 1 receptor
Positive ionotrophic and chronotropic effects on the heart; speeds conduction across the AV node.
What regulates heart contractility?
The balance between Gs and Gi stimulation. Both together have effects on Ca2+ levels leading to modification of the contractile responses in the heart. Beta 1 vs M2
Characterize the Beta 2 receptors.
located on vasculature. Increases blood flow to skeletal muscles.causes a relaxation of vascular, bronchial, gastrointestinal and genitourinary smooth muscle, stimulate the uptake of potassium into skeletal muscles, stimulates glycogenolysis and gluconeogenesis in the liver
Explain how it is that Beta 1 can cause cardiac contraction while Beta 2 causes smooth muscle relaxation both being Gs protein receptors?
Gs activation leads to increase AC and increased cAMP. Increase in cAMP in smooth muscle ctivates PKA causing phosphorylation of MLCK. Phosphorylated MLCK is inactive preventing binding to Ca2+ thereby preventing contraction.
What is the paradoxical effects on vaculature with regards to beta and alpha receptors?
Alpha 1 and Beta receptors are both located on the vasculature. At low concentrations Beta 2 receptors have a higher affinity to Epi causing a vasodilation, but as concentrations get larger the increase in alpha 1 stimulation overrides the beta 2 stimulation causing vasoconstriction
Characterize the Beta 3 receptors
Adipose tissue: lipolysis important source of energy from fat metabolism.