03 | Synaptic Transmission Flashcards
NMJ always use ___ NT and it is always ___. The receptor is always ___. The post-synaptic potential is called ___.
- ACh
- Excitatory
- nAChR
- End plate potential
Define: EEP
Depolarization of skeletal muscle caused by NT binding at NMJ
Schwann cells are support cells for the ___
PNS
What is a postsynaptic feature unique to NMJ?
Postjunctional folds (increase SA)
Distance between adjacent cells (value)
20 nm
Distance of synaptic cleft
20-45 nm
Ion that is prevalent at excitatory synapses
Na
Ion that is prevalent at inhibitory synapses
Cl
___ removes Cl from solution and inside cell
Isethionate
Which way does the ion flow at its reversal potential?
No flow because conc. gradient is balanced with electrical gradient
What is 1 difference between EPP and EPSP/IPSP?
EPP is degenerative (decrease with increasing distance from end plate)
What kind of synapse does presynaptic inhibition occur at?
Axoaxonic
Presynaptic inhibition is mediated by __ (NT) and __ (ion)
GABA, Cl
What kind of synapse does postsynaptic inhibition occur at?
axosomatic or axodendritic
Timing of EPSP and IPSP
If IPSP arrives before EPSP, excitation can’t happen. However, if IPSP arrives after EPSP, it will not stop the excitatory response.
Direct synapses use ___ receptors, while indirect synapses use ___ receptors.
- ionotropic
2. metabotropic
Define: autoinhibition
NT binds to metabotropic receptors on presynaptic membrane in order to feedback and stop NT release
List 3 examples of autoreceptors
- GABA(B)
- D2
- α2-adrenergic
Gs pathway
↑ AC ⇒ ↑ cAMP ⇒ ↑ PKA
Gq pathway
↑ PLC ⇒ IP3 ⇒ DAG ⇒ PKC + increase [Ca]i from intracellular stores (ER)
Gi pathway
↓ AC ⇒ ↓ cAMP ⇒ ↑ K channel opening ⇒ hyperpolarization
Go pathway
↓ Ca channel opening → ↓ NT release
G proteins are classified according to…
structure and target of α subunit
Effect of GPCR pathways depend on…
- Receptor
- G protein
- Effectors
- Arrangement of 1-3 (e.g. multi-protein complexes)
- NT
Where is the G protein binding domain on GPCR?
TM III to VII
How does GPCR work over short distances?
1) Ligand binds to receptor
2) GDP → GTP
3) G protein (with α, β, γ subunits) dissociates
4) β and γ subunit goes to ion channel and opens/close it (direct interaction)
Effect of ECBs
overall inhibition of CNS (stop pain)
Release of ECB
Produced in postsynaptic cell and released
- DOES NOT INVOLVE VESICLES
What does 2-AG bind?
CB1 receptor on presynaptic membrane
2-AG uses ___ inhibition
retrograde
Define: volume transmission
Signalling to neighbour neurons
What is volumen transmission called elsewhere in the body?
paracrine signalling
What molecules are used for volume transmission?
NO, CO
2 ways to increase [Ca]
- Ionotropic-Rs act as Ca ion channels
2. mRs act open intracellular Ca stores
How many Ca does CaM bind?
4
Effects of Ca-CaM complex
- Open Ca-CaM channel
- Activate CaM kinase
- Activate NO synthase
1 neuron can be connected with up to ___ neurons via electrical synapse
10
electrical synapses are joined together by ___
connexins
What is connexin-36?
6 TM connexons that form a pathway for current
Is chemical or electrical synapses more reliable? Why?
electrical, because it can’t be blocked by neurotoxins
