Chater 7 neuro 333333

Steps of chemical signaling

Signal; receptor; transduction; effector; response

Synaptic signaling

Short distance; between neurons

Paracrine signaling

Local signaling; nearby cells

Endocrine signaling

Long distance via bloodstream

Ionotropic receptor mechanism

Ligand binds → channel opens → ions flow

GPCR mechanism

Ligand binds → activates G-protein → signaling cascade

Enzyme-linked receptor mechanism

Ligand binds → activates enzyme → phosphorylation

Intracellular receptor mechanism

Ligand crosses membrane → alters gene expression

What activates G-proteins

GDP replaced by GTP

What happens after G-protein activation

Alpha subunit separates and activates effector

How G-proteins turn off

GTP hydrolyzed to GDP

Second messengers

cAMP; Ca2+; IP3/DAG

Function of second messengers

Amplify signal inside cell

Why one neurotransmitter has different effects

Different receptor types and signaling pathways

Cell-impermeant signaling molecules

Cannot cross membrane; require surface receptors

Cell-permeant signaling molecules

Cross membrane; bind intracellular receptors

Channel-linked receptors

Receptor is also ion channel

Enzyme-linked receptors

Usually kinases; phosphorylate targets

Intracellular receptors

Act as transcription factors

GPCR receptors

Activate intracellular signaling via G-proteins

Purpose of signaling cascades

Amplification, regulation, long-term changes