Synapses and synaptic potentials Flashcards
How many neurons are there app. in the human brain?
10^14-10^15
What are the three types of synapses according to placement on postsynaptic neuron?
Axo-dendritic, axo-somatic and axo-axonic
What are the two types of synapses according to mechanism?
Electrical and chemical
How does a electrical synapse transfer the signal?
Through gap junctions (direct transfer of currents)
What are some characterizations of electrical synapses?
They are fast, bi-directional, maintain the sign (depol–>depol/hyperpol–>hyperpol), function in synchronization, can vary their strength by opening/closing gaap junctions
How many % does the electrical synapses make up app.?
1 %
What is the active zone?
The place where vesicles fuse with the plasma membrane
What is the postsynaptic density?
The place where receptors are placed on the postsynapse
What is the definition of a NT?
1) it is present in the neuron, 2) it is liberated as a result of APs, and 3) it activates receptors in a postsynaptic cell
What type of transport does NT transporters use?
Secondary active
What is the definition of excitatory neurotransmission?
If it increases the probability that the postsynaptic neuron fires an AP
What are the mechanism behind excitatory neurotransmission?
Reversal potential > threshold
What is the reversal potential?
The reversal potential of an ion channel is the potential where the electrical current through the channel is 0 (equal amount of Na+ goes into the cell as K+ goes out)
What is the reversal potential of an ion channel permeable to one ion?
The ions Nernst potential
What is the reversal potential of an ion channel permeable to two ions?
The in-between Nernst potential of the two ions
What is the definition of inhibitory neurotransmission?
If it reduces the probability that the postsynaptic neuron fires an AP
What is the mechanism of inhibitory neurotransmission?
Reversal potential < threshold
What are the diference between spatial and temporal transmission?
Spatial: mulitple synapses fire together to strengthen the signal
Temporal: one synapse fires multiple times in a row to strengthen the signal
What is shunting inhibition?
When an inhibitory synapse short circuits an entire dendrite, by reducing the length constant
Are vesicle membranes negatively or positively charged?
Positively
What determines if a synapse is inhibitory or excitatory?
The postsynaptic receptors reversal potential
What are the function of botulinum toxin?
It is a protease targeting the SNARE complex, breaking down one of the proteins
What is the function of alfa-lactotoxin?
Also targets the SNARE complex, but stimulates it
Where in the SNARE cycle are ATP required?
At the fusion with the PM –> release of NT
How does synaptotagmin work?
It’s a Ca2+ sensor: triggers membrane fusion when Ca2+ is bound, inhibits when not
When Ca2+ binds the electrostatic properties switch –> reduces repulsion
App. how many APs actually end in NT release?
30 %
How are synaptic vesicles locally recycled?
By the clathrin-dependent endocytosis
True or false: there might be several different endocytosis routes, and some are not dependent on clathrin.
True
What other types of proteins are found in the postsynaptic density?
Many types, e.g., anchoring proteins such as PSD95
How are the pre- and postsynapses aligned?
In nanocolumns
What bridged the synaptic cleft?
Transsynaptic protein pairs
How are transsynaptic protein pairing involved in synaptogenesis?
Expression of postsynaptic adhesion proteins in non-neuronal cells stimulate neurons to form presynapses, and xxpression of presynaptic adhesion proteins in non-neuronal cells stimulate neurons to form postsynapses
What are the fast and reversible effects of intracellular signaling?
Protein phosphorylation –> changes in protein functions
What are the slow and long-lasting effects of intracellular signaling?
Transcriptional regulation –> changes in protein composition
What are CREB, and does it work?
cAMP response element binding protein
Receptor activation –> –> CREB activation –> transcription –> translation
Where does CREB play a role?
In late-phase LTP
What is C-fos?
A transcription factor and a marker for activated neurons
