principles pharmacology Flashcards
(56 cards)
paracrine signals
produces by cell, targets nearby cells
what are autocrine signals
cell to its own receptors
endocrine signals
targets specific cells far away from source (hormones)
hydrophobic ligands
cannot freely stay in ECM, brought into cells via carrier proteins
hydrophilic ligands
signals move freely through ECM, bind to surface receptors on cell
what are the stages of cell signalling
reception - recetor binds to ligand
transduction - receptor protein changes, activates intracellular molecules
cell response
what are the 3 classes of signalling pathways
- G-protein coupled receptors
- enzyme coupled receptors
- ion channel receptors
describe ligand-gated ion channels
- response within milliseconds
Steps
- Ligand binds to the receptor, channel opens
- Ions (Ca2+, Na+, K+) flow through passively
- Triggers signalling pathway
ex
- Nicontinic acetylcholine receptors
describe G-protein coupled receptors
- response happens in seconds
signal travels far due to signal amplification
describe the steps for turning a G-protein coupled receptor on
- Agonist (ligand) activates G-coupled receptor
- ⍺ subunit leaves G-protein
- GDP exchanged for GTP (guanine nucleotide exchange)
- Triggers other proteins in signaling pathway
describe the steps for turning a G-protein coupled receptor off
- ⍺ subunit hydrolyses GTP → GDP
- disactivating G-protein
- ⍺ subunit recombines with β𝛾 subunit
example of G-protein coupled receptors
- Adrenoceptors – bound and activated by the neurotransmitters/hormones adrenaline and noradrenaline
- Adrenalinebinding tob2-adrenoreceptors→ Causes bronchodilation
describe enzyme coupled receptors
- Response occurs in hours
- Single pass transmembrane proteins
- multiple pathways activated
what are the functions of the autonomic nervous system
Mediates output from whole body except skeletal muscle, regulated by external and internal sensory input, via reflexes
- maintained homeostasis through negative feedback loop
sympathetic transmitter for preganglionic neurones and postganglionic neurones
- acetylcholine (ACh)
- noradrenaline (NA)
parasympathetic transmitter for both
acetylcholine (ACh)
β1: Gs stimulation of adenylyl cyclase →
inc HR and force of contraction
β2: Gs stimulation of adenylyl cyclase →
bronchodilation
M1: Gq (stimulation of phospholipase C) →
inc stomach acid secretion
M2: Gi (inhibition of adenyl cyclase; opening of K+ channels, closure of Ca2+ channels) →
decreased HR
M3: Gq (stimulation of phospholipase C) →
bronchoconstriction
what does action potential allow
signalling over long distances
lower Ka =
greater affinity of ligand for receptor
antagonist
drug that reduces or inhibits the actions of an agonist by binding to the same receptor
