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SFI Test 1 > Synaptic Transmission > Flashcards

Synaptic Transmission Flashcards

1
Q

What is the function of the synapse?

A

Transmit information over short distances

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2
Q

What are the features of an electrical synapse?

A

Capacitive current flows directly from presynaptic axon to postsynaptic cell via gap junctions

Very small synaptic cleft

Postsynaptic response can only be excitatory (depolarizing)

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3
Q

What are the features of a chemical synapse?

A

Capacitive current ends at axon terminal

Axon terminal releases neurotransmitters that can produce either an excitatory or inhibitory response

Effect not determined by size

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4
Q

What are the two key organelles located at the axon terminal?

A

Mitochondria

Synaptic vesicles – storage for neurotransmitters

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5
Q

How are synaptic vesicles loaded with neurotransmitters?

A

ATP transporter pumps protons into the vesicle

Proton transporter exchanges protons for neurotransmitter molecules into the vesicle

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6
Q

What is the active zone?

A

Protein dense area that is the site of transmitter release

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7
Q

Describe the extracellular matrix at a synapse.

A

Structural alignment of pre and postsynaptic elements

Presence of AChE enzyme for ACh breakdown (only at cholinergic synapses)

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8
Q

What types of proteins are located at the postsynaptic density?

A

Receptors and cytoskeletal proteins

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9
Q

What does an action potential reaching the axon terminal cause?

A

Open of voltage-gated Ca channels in the active zone

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10
Q

Describe the driving force for calcium at the synaptic terminal.

A

Will be inward at any potential between Ek and Ena

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11
Q

What is synaptobrevin?

A

v-SNARE protein that is associated with the vesicle membrane

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12
Q

What are SNAP-25 and syntaxin?

A

t-SNARE proteins that are associated with the membrane at the active zone

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13
Q

What is docking?

A

The connection of the v- and t- SNARE proteins that holds the vesicle at the active zone

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14
Q

What is priming?

A

The zipping of the v- and t-SNAREs pulls the vesicle extermely close to the plasma membrane so that it is ready to fuse

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15
Q

What is synaptotagmin?

A

Calcium sensor protein that triggers the fusion process

Located on the vesicle

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16
Q

What happens when synaptotagmin binds calcium?

A

Increases lipid solubility and moves into the lipid bilayer

This drags the vesicle even closer to the plasma membrane, which causes spontaneous fusion

17
Q

What are the two mechanisms of exocytosis?

A

Kiss and Run - membranes do not completely fuse

Complete fusion - fusion pore dilates and the membranes completely fuse

18
Q

What is mobilization?

A

Allows vesicles to be released from the reserved pool and be docked and primed

19
Q

What is synapsin?

A

Tethers reserved vesicles to the actin cytoskeleton

20
Q

How are reserved vesicles mobilized?

A

Influx of calcium causes the phosphorylation of synapsin, which causes it to dissociate from the actin and release the vesicle

21
Q

What are three ways calcium is regulated in the axon terminal?

A

Plasma membrane transporters - pump it out

Sequestration into organelles - primarily mitochondria

Calcium binding proteins in cytoplasm

22
Q

How are calcium influx and phosphorylation of synapsin related?

A

Phosphorylation is proportional to the amount of free calcium in the cytoplasm

23
Q

How is free calcium and action potential frequency related?

A

Free calcium is proportional to action potential frequency

More action potentials –> more calcium –> more synapsin phosph. –> more vesicle mobilization

24
Q

What is a Quantal?

A

One quantum = amount of transmitter in one vesicle

25
Q

What are the two methods of terminating transmitter action?

A

Diffusion and enzymatic degradation (cholinergic synapses only)

Diffusion and reuptake

26
Q

What enzyme is responsible for enzymatic degredation of acetylcholine?

A

Acetylcholinesterase

27
Q

How is glutamate returned to the presynaptic terminal?

A

Glutamate is taken up by glial cells

In glial cells, glutamate is converted to glutamine and exported

Glutamine is returned to the presynaptic terminal, where it is converted back to glutamate

28
Q

How are vesicles recycled?

A

Clathrin-dependent endocytosis

*know the role of dynamin

SFI Test 1 (14 decks)

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