Transmission + NTs Flashcards
How many connexin subunits make up 1 connexon (hemichannel)?
6
Gap junctions are formed from 2 ______ between two neurones?
Hemichannels (connexon)
Distance across an electrical synapse is?
Distance across chemical synapse is?
3.5nm
30-50nm
Electrical synapses function by what agent of transmission?
Ionic current
Synaptic delay:
- Electrical?
- Chemical?
- none
- 1-5 ms (min 0.3ms)
Are chemical/electrical synapses unidirectional or bidirectional?
Chemical: unidirectional
Electrical: bidirectional
Peptide NTs are synthesised in ___ and stored in___?
Amine and AA NTs are synthesised in ___ and stored in___?
Cell body, large dense core vesicles (90-250nm)
Synaptic terminal, small clear vesicles (40-60nm)
A single neurone can produce and release >1 NT. This is called?
Co-existence / co-transmission
Which vesicle bound SNARE protein binds to SNAP-25 causing vesicle docking/priming?
Synaptobrevin
What is synaptotagmin and what role does it have?
- Vesicle bound SNARE protein
- Ca sensor
- Involved in fusion of vesicle to montane
What is an MEPP and an EPP?
(Miniature) end plate potential
EPP = multiples of MEPPs (single vesicle release)
EPP is action potential dependent
An IPSP is due to influx of which ion?
Cl-
Which type of synapse is more common, electrical or chemical?
Chemical
Glutamate is removed from synapse by?
EAATs (excitatory amino acid transporters)
- in glial cells and presynaptic terminal
Glutamate taken up into glial cells is converted to _____ by ________?
Glutamine
Glutamine synthase
Precursor for glutamate is___?
Converted to glutamate by what enzyme?
GLUTAMINE
Glutaminase
Too much glutamate can be toxic to neurones. This is called____? And can cause?
Excitotoxicity
Epilepsy, ischemia, hypoglycemia
GABA is synthesised from _____ by ______?
Glutamate
Glutamic acid decarboxylase (an co-factor pyridoxal phosphate, vit B6 derivative)
GABA is removed from synapse and taken up into glia and neurones by____?
GABA transporters
Na dependent co-transporters
Effects of benzodiazepines, barbiturates and alcohol work by _______ of GABA signalling?
Potentiation
Co-release of small molecule and peptide NTs occurs at what kind of stimulation?
High frequency stimulation
NB: only small molecule NTs released at low freq stimulus
How many transmembrane domains do subunits of IONOTROPIC receptors have?
4 transmembrane helices
Or 3 + pore loop
The nicotinic Ach R is permeable to which ions,?
Na+
K+
Sometimes Ca2+
Glutamate IONOTROPIC receptors have how many subunits?
4 (tetramer)
Which IONOTROPIC receptors are pentamers?
GABA, nACh, 5-HT, Glycine
The co-agonist for the NMDA receptor is?
Glycine
Why is NMDA receptor only active during high frequency stimulation?
In hyperpolarized state Mg2+ blocks pore
Depolarization removes Mg2+
How many subunits do METABOTROPIC receptors have?
One
They are MONOMERIC
Extracellular domain of metabotropic receptors made up of domains ____?
2,3,6+7
G protein binds to which domains of metabotropic intracellular domain?
Loop between domains 5 and 6
C-terminus
What type of synaptic connection controls NT release?
Axo-axonic
Axo-dendritic synapses are usually inhibitory or excitatory?
Excitatory
What is neural integration?
Summation of EPSPs and IPSPs
Multiple synaptic potentials combine within one postsynaptic neurone
Occurs at axon hillock
Temporal summation is…
One synaptic input
APs fired in quick succession
Spatial summation…
> 1 synaptic input arrive at same time
Axo-somatic synapses occur at the ______?
Axon hillock
Normal direction of AP propagation is…?
Orthodromic
