Chemistry and Physiology of the Synapse Flashcards
There are 2 classes of postsynaptic receptors, what are they called?
- ligand gated (ionotrophic) and G-protein coupled (metabotrophic)
- ion gated (ionotrophic) and G-protein coupled (metabotrophic)
- ligand gated (ionotrophic) and ion gates (metabotrophic)
- receptor tyrosine kinase (ionotrophic) and G-protein coupled (metabotrophic)
- ligand gated (ionotrophic) and G-protein coupled (metabotrophic)
- ionotrophic = ion sensitive
- metabotrophic = associated with metabolic pathways
How do ligand gated channels work?
- ligand binds with receptor on ligand gated receptor
- ligand gated receptor undergoes conformational change creating a pore/channel
- ions to cross the membrane (creates gradient membrane)
Why are metabotropic receptors given this name?
- the eventual movement of ions through a channel will require one or more metabolic steps
- GDP to GTP for example to activate the G protein and intracellular pathways
Why are ionotropic receptors given this name?
- once ligand binds ion channels are formed
- ions can enter or leave the cell
How do G protein coupled channels work?
- ligand binds to binding site
- G protein inside cell activates intracellular pathway
Do ligand gated (iontropic) or G-protein coupled (metabotropic) receptors have a faster transmission?
- ligand gated channels
- dont require all the intracellular steps associated with the GPCRs
What does GLuR mean?
- GLu = glutamate
- R = receptor
- Glutamate Receptor
What is glutamate?
- an amino acid ingested in the diet
- functions as an excitatory neurotransmitter
What are the 3 types of ionotropic glutamate receptors, that are defined by the agonist of the receptor?
- AMPA (main one), NMDA, Kainate
- Na+ channel (main one), NMDA, Kainate
- GPCR (main one), NMDA, Kainate
- AMPA (main one), K+ channel, Kainate
- AMPA (main one), NMDA, Kainate
- AMPA (main excitatory channel)
- NMDA (has a Mg+ molecule that inhibits it
- Kainate
AMPA is a glutamate receptor. What happens to the AMPA receptors if glutamate binds with it?
- conformational change, opens Na+ channels and re-polarisation
- conformational change, opens Na+ channels and hyper-polarisation
- conformational change, opens K+ channels and de-polarisation
- conformational change, opens Na+ channels and de-polarisation
- conformational change, opens Na+ channels and de-polarisation
- the receptor has a conformational change
- conformational changes makes it specific to Na+ ions
- action potential occurs at post synaptic neuron
Glutamate NMDA is a glutamate receptor. The NMDA receptor is composed of 2 identical subunits. In addition to glutamate, what else is required to bind with the NMDA receptor to try and initiate an action potential?
- glycine
- glutathione
- gamma-amino-butyric acid
- dopamine
- glycine
Glutamate NMDA is a glutamate receptor. The NMDA receptor is composed of 2 identical subunits. Glutamate and glycine (both neurotransmitters) bind to a subunit each. This can open the channel allowing Ca2+ to flow into the cell. However, this can also be insufficient alone to remove the Mg2+. What else can contribute to NMDA receptors to open?
- multiple graded potentials
- increased glycine binding
- decreased K+ leaving the cell
- increased glutamate binding
- multiple graded potentials
- multiple NMDA receptors allows the charge to cross the threshold for an action potential
- charge around NMDA receptor is changed and the Mg2+ inhibitor is removed
- Ca2+ then flows into the cell creating an action potential
What does GABA stand for and what is it?
- Gamma Aminobutyric Acid
- a neurotransmitter
GABA can bind to a ligand gated channel that is able to inhibit the post synaptic membrane. How does it do this?
- influx of Cl-
- opening K+ channels and K+ leaves the cell
- closes Na+ channels so Na+ cannot enter the cell
- inhibits Na+ channels
- causes an influx of Cl-
* results in hyperpolarisation and inhibits action potentials
Where is the acetylcholine (ACh) ionotropic receptor found in the body?
- neuromuscular junction
- binds with 2 ACh ligands using the 2 a subuntis
Which receptor is present in aprox 90% of brain synapses?
- NMDA
- dopamine
- AMPA
- tyrosine
- AMPA receptors
If stimulus has been supplied glutamine will be released into the synaptic cleft and bind to the glutamine receptors AMPA and NMDA receptors. But if the signal is not sufficiently strong what happens with the AMPA and NMDA receptors?
- AMPA receptors are generally stimulated causing small depolarisation
- NMDA does not open due to Mg2+ blocking the pore
If stimulus has been supplied glutamine will be released into the synaptic cleft and bind to the glutamine receptors AMPA and NMDA receptors. If the signal is sufficiently strong what can happen to the AMPA and NMDA receptors?
- AMPA channels open depolarising the post synaptic neuron (Na+ influx)
- Mg2+ previously blocking the NMDA channel is removed (N+ and Ca2+ influx)
What is synaptic integration?
- the process where all signals to a neuron are combined prior to generating an action potential
- more inhibitory signals = hyperpolarisation
- more excitatory signals = depolarisation
When norepinephrine (a neurotransmitter) binds to its respective ligand binding site on the GPCR (Gas) what is the intracellular pathway to elicit its target reaction of increasing protein phosphorylation?
- adenylyl cyclase (effector protein) converts ATP into cAMP
- cAMP (second messenger) activates protein kinase A
- increased protein kinase A (later effectors)
- protein kinase A increases protein phosphorylation
When glutamate (a neurotransmitter) binds to its respective ligand binding site on the GPCR (Gq) what is the intracellular pathway to elicit its target reaction of increasing protein phosphorylation and activation of Ca2+ binding proteins?
- phospholipase C (effector protein) cleaves PiP2 into IP3 and DAG
- IP3 (second messenger) binds to sarcoplasmic reticulum, releasing Ca2+ (second messenger)
- Ca2+ binds with DAG and activates protein kinase C (pKC)
- pKC increases protein phosphorylation and activation of Ca2+ binding proteins
When dopamine (a neurotransmitter) binds to its respective ligand binding site on the GPCR (Gi) what is the intracellular pathway to elicit its target reaction of decreasing protein phosphorylation?
inhibits Gas on GPCR
1 - inhibits adenylyl cyclase
2 - causes reduced cAMP and protein kinase A
