Physiology Flashcards
G-protein coupled receptors
7 transmembrane domain associated with G-protein. G-protein has alpha, beta, gamma subunits. Alpha subunit bound to ATP. Once GPCR binds ligand, ATP cleaved releasing G protein to activate second messengers.
G-protein coupled receptors associated with Gq
- “HAVe 1 M and M”
- H1
- Alpha 1
- V1
- M1
- M3
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G-protein coupled receptors associated with Gs
- Beta 1
- Beta 2
- Beta 3
- D1
- H2
- V2
- Glucagon
- PTH
- TSH
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G-protein coupled receptors associated with Gi
- MAD 2s.
- M2
- Alpha 2
- D2
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Cyclic GMP second messenger system
- Natriuretic peptides- BNP, ANP
- Nitric oxide
- G protein stimulates guanylate cyclase (GC)–>turns GTP into cGMP–> activates protein kinase G–> smooth muscle relaxation.
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Gi second messenger system
Ligand binds to R–> Gi activation–> decreases AC activity–> ATP not converted into cAMP–> cAMP does not activate PKA–> PKA does not inactivate MLCK allowing for myosin phosphorylation and smooth muscle contraction. PKA does not increase intracellular calcium in heart muscle.
Gs second messenger system
Ligand binds to R–> Gs activation–> increases adenylyl cyclase–> turns ATP into cAMP–> cAMP activates Protein Kinase A (PKA). PKA increases intracellular calcium concentrations in the heart. PKA decreases intracellular calcium concentrations in smooth muscle (eg, bronchioles) and inhibits myosin light-chain kinase (thus inhibiting myosin phosphorylation and smooth muscle cell contraction contraction).
Gq second messenger system
Ligand binds to R–>Gq activation–>Phospholipase C–> breaks up lipid membrane PIP2 into DAG and IP3. DAG–> Protein Kinase C (PKC). IP3–> liberates intracellular Ca2+ from endoplasmic reticulum–> smooth muscle contraction.
Alpha 1 receptor
- Sympathetic nervous system: Gq
- Increases vascular smooth muscle contraction (increased SVR)
- Increased pupillary sphincter muscle contraction (mydriasis)
- Increased intestinal and bladder sphincter muscle contraction (urinary retention).
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Alpha 2 receptor
- Sympathetic nervous system: Gi
- Decreased sympathetic (adrenergic outflow)
- Decreased insulin release
- Decreased lipolysis
- Increased platelet aggregation
- Decreased aqueous humor production
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Beta 1 receptor
- Sympathetic nervous system: Gs
- Increased heart rate
- Increased contractility
- Increased renin release
- Increased lipolysis
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Beta 2 receptor
- Sympathetic nervous system: Gs
- Vasodilation
- Bronchodilation
- Increased lipolysis
- Increased insulin release
- Decreased uterine tone (tocolysis)
- Ciliary muscle relaxation
- Increased aqueous humor production
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Beta 3 receptor
- Sympathetic nervous system: Gs
- Increased lipolysis
- Increased thermogenesis in skeletal muscle
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M1 receptor (muscarininc AChR)
- Parasympathetic nervous system: Gq
- CNS
- Enteric nervous system
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M2 receptor (muscarininc AChR)
- Parasympathetic nervous system: Gi
- Decreased heart rate
- Decreased atrial contractility
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