The physiologic "fear" response is associated with the signaling activity of adrenergic receptors stimulated by epinephrine/norepinephrine.b9bG protein–coupled receptor (GPCR)G protein–coupled receptor (GPCR)Protein Kinase CAKA adrenalineProtein Kinase Ainositol 4,5-biphosphatediacylglycerolinositol triphosphate"There are ten known isoforms of adenylyl cyclases in mammals" [https://en.wikipedia.org/wiki/Adenylyl_cyclase]Activation"List of the steps involved in PKA activation:
1. Cytosolic cAMP increases.
2. Two cAMP molecules bind to each PKA regulatory subunit.
3. The regulatory subunits move out of the active sites of the catalytic subunits and the R2C2 complex dissconnects.
4. The free catalytic subunits interact with proteins to phosphorylate Ser or Thr residues." [https://en.wikipedia.org/wiki/Protein_kinase_A#Activation]Activation"List of the steps involved in PKA activation:
1. Cytosolic cAMP increases.
2. Two cAMP molecules bind to each PKA regulatory subunit.
3. The regulatory subunits move out of the active sites of the catalytic subunits and the R2C2 complex dissconnects.
4. The free catalytic subunits interact with proteins to phosphorylate Ser or Thr residues." [https://en.wikipedia.org/wiki/Protein_kinase_A#Activation]norepinephrine signaling pathwayPW:0000791Pathway Ontologyepinephrine signaling pathwayPW:0000790Pathway Ontology9780813546773ISBNThe Fats of Life: Essential Fatty Acids in Health and DiseaseRutgers University Press; ISBN 978-0-8135-4677-32010Glen D. Lawrenceclassic metabolic pathwayPW:0000002Pathway Ontology