The Post Synaptic Terminal Flashcards
What are dendritic spines?
spines are made up of a head and neck and exist as bumps on the dendrite
What are the functions of dendritic spines?
Increased surface area to optimise packing of synapses
Serve as separate electrical units, modulating the synaptic signals
Provide biochemical compartments that restrict the mobility of molecules
How do the sizes of dendritic spines vary and what does size mean for their function?
The dendritic spines vary a lot in size, smaller spines have a smaller amplitude of responses.
How does the morphology of the dendritic spine affect its electrical resistance?
If the neck is smaller, or longer in length then there will be a greater electrical resistance .
R=pL/CSA
How does the morphology of the dendritic spine affect its chemical resistance?
Longer or narrower neck = more resistance.
How can you compare the electrical resistance of a dendritic spine, and its morphology?
FRAP can be used; dye injected then photobleached in the head and neck, then fluorescence recovery measures time taken for dye to return to head; this measurement is then compared to the neck width and length.
How can you compare the chemical resistance of a dendritic spine to its morphology?
Caged glutamate becomes freed when exposed to laser light; use this on varying dendritic spines and see how signal produced is affected by morphology
What does FRAP stand for?
Fluorescence recovery after photobleaching
What are the two types of glutamate receptors?
AMPA and NMDA
What are nanocoloumns
Arrangements of neurotransmitters so that they are directly opposed from the active zone by scaffold proteins keeping them at the synaptic cleft by a trans-synaptic adhesion complex.
Describe the architecture of the scaffolding of NMDARs
(primary and secondary scaffolding)
Attached to PSD-95 (post-synaptic density protein 95) on PDZ domain, which anchors it to the actin frame.
Describe the architecture of the scaffolding of AMPARs
AMPA - TARP - PSD95 - Actin frame
PSD-95 has a PDZ domain that helps it interact with NMDAs directly, but in this case AMPA uses TARP to attach to PSD-95
TARP = transmembrane AMPAR regulatory protein PSD-95 = post synaptic density protein 95
Describe the structure of an ACh receptor
Pentamer
Monomers have 4 transmembrane domains, which twist when ACh binds, opening the pore
What is an ionotropic receptor?
Ligand gated ion channels
Describe the structure of a glutamate receptor
Tetramer with 3 transmembrane domains.
Describe how the glutamate receptor opens
Transmembrane domains are pulled apart and then begin to relax until they are closed even when glutamate bound (desensitised state).
What ions can pass through glutamate receptors?
Mostly Na+ and K+
What is the electrical effect of glutamate binding to its receptor?
Causes inward current called EPSC (excitatory post synaptic current), which causes a transient depolarisation in the post synaptic neuron (EPSP)
Which glutamate receptor is the fast one and which is the slow one?
AMPA = fast NMDA = slow
What happens when glutamate binds to an AMPA receptor?
Ligand binds, k+ and Na+ (and sometimes Ca2+) pass through fast acting
What happens when glutamate binds to an NMDA receptor?
Ligand binds and depolarisation needed as well for Mg+ plug to be removed, Na and Ca can pass through, slower acting
Where on the dendrite are inhibitory/excitatory synapses found?
inhibitory = main body of dendrite Excitatory = dendrite spines
What is the structure of a GABA receptor
Pentamer (2a, 2b, y), GABA binds in between a and b subunits.
What is the function of the GABA receptor
GABA receptors move Cl- ions into the neuron which causes hyperpolarisation of the post synaptic neuron, making it more difficult exceed the threshold required for an action potential to take place therefore having an inhibitory effect on the firing of the neuron
