Synapses and synaptic potentials

Question 1

How many neurons are there app. in the human brain?

Answer 1

10^14-10^15

Question 2

What are the three types of synapses according to placement on postsynaptic neuron?

Answer 2

Axo-dendritic, axo-somatic and axo-axonic

Question 3

What are the two types of synapses according to mechanism?

Answer 3

Electrical and chemical

Question 4

How does a electrical synapse transfer the signal?

Answer 4

Through gap junctions (direct transfer of currents)

Question 5

What are some characterizations of electrical synapses?

Answer 5

They are fast, bi-directional, maintain the sign (depol–>depol/hyperpol–>hyperpol), function in synchronization, can vary their strength by opening/closing gaap junctions

Question 6

How many % does the electrical synapses make up app.?

Answer 6

1 %

Question 7

What is the active zone?

Answer 7

The place where vesicles fuse with the plasma membrane

Question 8

What is the postsynaptic density?

Answer 8

The place where receptors are placed on the postsynapse

Question 9

What is the definition of a NT?

Answer 9

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

Question 10

What type of transport does NT transporters use?

Answer 10

Secondary active

Question 11

What is the definition of excitatory neurotransmission?

Answer 11

If it increases the probability that the postsynaptic neuron fires an AP

Question 12

What are the mechanism behind excitatory neurotransmission?

Answer 12

Reversal potential > threshold

Question 13

What is the reversal potential?

Answer 13

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)

Question 14

What is the reversal potential of an ion channel permeable to one ion?

Answer 14

The ions Nernst potential

Question 15

What is the reversal potential of an ion channel permeable to two ions?

Answer 15

The in-between Nernst potential of the two ions

Question 16

What is the definition of inhibitory neurotransmission?

Answer 16

If it reduces the probability that the postsynaptic neuron fires an AP

Question 17

What is the mechanism of inhibitory neurotransmission?

Answer 17

Reversal potential < threshold

Question 19

What are the diference between spatial and temporal transmission?

Answer 19

Spatial: mulitple synapses fire together to strengthen the signal
Temporal: one synapse fires multiple times in a row to strengthen the signal

Question 19

What is shunting inhibition?

Answer 19

When an inhibitory synapse short circuits an entire dendrite, by reducing the length constant

Question 19

Are vesicle membranes negatively or positively charged?

Answer 19

Positively

Question 20

What determines if a synapse is inhibitory or excitatory?

Answer 20

The postsynaptic receptors reversal potential

Question 21

What are the function of botulinum toxin?

Answer 21

It is a protease targeting the SNARE complex, breaking down one of the proteins

Question 22

What is the function of alfa-lactotoxin?

Answer 22

Also targets the SNARE complex, but stimulates it

Question 23

Where in the SNARE cycle are ATP required?

Answer 23

At the fusion with the PM --> release of NT

Question 24

How does synaptotagmin work?

Answer 24

It's a Ca2+ sensor: triggers membrane fusion when Ca2+ is bound, inhibits when not When Ca2+ binds the electrostatic properties switch --> reduces repulsion

Question 25

App. how many APs actually end in NT release?

Answer 25

30 %

Question 26

How are synaptic vesicles locally recycled?

Answer 26

By the clathrin-dependent endocytosis

Question 27

True or false: there might be several different endocytosis routes, and some are not dependent on clathrin.

Answer 27

True

Question 28

What other types of proteins are found in the postsynaptic density?

Answer 28

Many types, e.g., anchoring proteins such as PSD95

Question 29

How are the pre- and postsynapses aligned?

Answer 29

In nanocolumns

Question 30

What bridged the synaptic cleft?

Answer 30

Transsynaptic protein pairs

Question 31

How are transsynaptic protein pairing involved in synaptogenesis?

Answer 31

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

Question 32

What are the fast and reversible effects of intracellular signaling?

Answer 32

Protein phosphorylation --> changes in protein functions

Question 33

What are the slow and long-lasting effects of intracellular signaling?

Answer 33

Transcriptional regulation --> changes in protein composition

Question 34

What are CREB, and does it work?

Answer 34

cAMP response element binding protein Receptor activation --> --> CREB activation --> transcription --> translation

Question 35

Where does CREB play a role?

Answer 35

In late-phase LTP

Question 36

What is C-fos?

Answer 36

A transcription factor and a marker for activated neurons