Central synapses Flashcards
How does the patch-clamp technique allow visually guided recordings from specific neuronal subtypes
The blunt electrode tips can be readily observed under a light microscope, ans the target neurons chosen on the basis of morphology and expression of fluorescent proteins
What is the benefit of simultaneous recordings from 2 connected neurons
Paired recordings enables precise control of action potential firing in the presynaptic neuron and the recording of a unitary postsynaptic response
Between what size neurons is electrical coupling effective
2 neurons of a similar size and thus impedance
What type of neurons do electric synapses occur betwee
Mostly occur between the dendrites of neurons of the same subtype
What structure forms electrical synapses
2 hemichannels or connexons that are made up of 6 connexins and connect across the intracellular space
What happens to the signal as it propagates through the electrical synapse
Attenuated and low-pass filtered meaning a 30mV step depolarisation of the presynaptic neuron produces a 3mV depolarisation of the postsynaptic neuron, and the presynaptic action potentials are only observed as spikelets
What type of communication do electrical synapses allow
Graded (proportional to strength of stimulus, not all-or-nothing, can be hyperpolarising or depolarising) and bidirectional communication
Over what distance can electrical synapses allow communication
Only allow short-distance communication as dendrites must be local
Examples of amine neurotransmitters
Noradrenaline, dopamine, serotonin
Examples of amino acid neurotransmitters
Glutamate and glycine
Examples of peptide neurotransmitters
Enkephalin and substance P
Example of soluble gas neurotransmitter
NO
What are the 2 most common neurotransmitters used in the CNS
Half the synapses in CNS use excitatory glutamate, while a quater use inhibitory gamma-aminobutyric acid (GABA)
What does GABA stand for
Gamma-aminobutyric acid
What is Dale’s principle
All axonal branches of a neuron release the same neurotransmitter substance/s (however, each neuron will often co-release more tan one type of neurotransmitter)
What are the 2 groups that chemical synapses can be sorted into
Gray’s Type 1/excitatory glutamergic synapses and Gray’s Type 2/inhibitory GABAergic synapses
What are Gray’s Type 1/excitatory glutamergic synapses
Have spherical vesicles, thicker postsynaptic density (asymmetrical), and found on dendritic spines and dendritic shafts
What are Gray’s Type 2/inhibitory GABAergic synapses
Flattened or elongated vesicles, symmetrical pre and post synaptic width, occur primarily on dendrite shafts, neuronal cell bodies and the axon initial segment
How is glutamate synthesised
Synthesied from glutamine by glutaminase
What concentrates glutamate in vesicles
Vesicle glutamate trasporters (vGluTs)
What are the range of ligand-gated ion channels glutamate can activate
Ionotropic glutamate receptors (iGluR) are categorised based on the binding/efficacy of different ligands- AMPA, kainate and NMDA receptors
What are the G protein-coupled receptors glutamate can activate
Metabotropic glutamate receptors, mGluR
What terminates synaptic transmission of glutamate
Glutamate diffuses out of the synaptic cleft and is then removed from the extracellular fluid via excitatory amino acid transporters (EAATs) expressed in presynaptic terminals, postsynaptic neurons and astrocytes
What does the predominant reuptake/recycling pathway appear to be via (which excitatory amino acid transporters) for glutamate
Astrocytes- convert glutamate to glutamine via glutamine synthetase, and release it into the extracellular space from which it is taken up by neurons