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neurobiology > Neurobio Exam 2 > Flashcards

Neurobio Exam 2 Flashcards

1
Q

How does information transfer occur at chemical synapses?

A

Electrical depolarization of the nerve terminal causes the release of chemicals that open postsynaptic ligand-gated ion channels which pass current, depolarizing the postsynaptic cell.

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2
Q

Dendritic spines are commonly a site for

A

excitatory synaptic transmission.

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3
Q

How does acetycholinesterase function at synapses that release acetylcholine?

A

It is a synaptic cleft enzyme that breaks down the transmitter acetylcholine.

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4
Q

How do transmitters act on the postsynaptic cell at direct chemical synapses?

A

They bind to ligand-gated ion channels to induce postsynaptic current flux.

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5
Q

Synaptic vesicles are concentrated in large numbers within nerve terminals. What is their function?

A

They store and release chemical transmitter molecules.

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6
Q

Why does the plant alkaloid nicotine cause skeletal muscle contraction?

A

Nicotine is an agonist at postsynaptic nicotinic acetylcholine receptors.

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7
Q

How does the technique called ionophoresis work?

A

Molecules inside a glass pipet can be expelled by electrical charge.

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8
Q

Molecules inside a glass pipet can be expelled by electrical charge.

A

They are highly concentrated directly under the presynaptic terminal at the NMJ.

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9
Q

What is the reversal potential for a channel?

A

The membrane potential at which the net current flux through a channel is zero, and on either side of which the net current flux moves in opposite directions

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10
Q

What is the principal excitatory transmitter in the CNS?

A

Glutamate

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11
Q

When comparing direct and indirect synaptic transmission, indirect synaptic transmission

A

is mediated by metabotropic receptors that activate intracellular second-messenger pathways

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12
Q

The G proteins that are coupled to metabotropic receptors are

A

heterotrimeric GTP binding proteins made up of α-, β-, and γ-subunits.

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13
Q

For G protein-coupled metabotropic receptors, GTP binds to the

A

α-subunit of the heterotrimer.

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14
Q

How is G protein-mediated signaling terminated?

A

Hydrolysis of GTP to GDP by the endogenous GTPase activity of the α-subunit leads to reassociation of the αβγ-complex, terminating the response.

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15
Q

The particular neurotransmitter present at a synapse

A

does not indicate the subtype of G protein or second messenger that will be coupled to the receptor

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16
Q

What would happen to metabotropic signaling in a cell if you added GTP-γ-s to the cell cytoplasm?

A

This would irreversibly activate all G protein-coupled metabotropic signaling.

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17
Q

What happens when PIP2 is cleaved by PLC?

A

This cleavage generates inositol-1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) that act as second messengers.

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18
Q

How many transmembrane domains do all G protein-coupled metabotropic receptors have?

A

All G protein-coupled metabotropic receptors has 7 transmembrane domains

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19
Q

Which of the following neurotransmitters is not stored in synaptic vesicles?

A

Endocannabinoids

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20
Q

The particular neurotransmitter present at a synapse

A

does not indicate the subtype of G protein or second messenger that will be coupled to the receptor.

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21
Q

What explains why there is a threshold depolarization of about 45 mV above resting membrane potential before any transmitter release occurs?

A

This is the magnitude of depolarization required to activate presynaptic voltage-gated calcium channels.

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22
Q

Which is both necessary and sufficient to trigger chemical transmitter release from a presynaptic nerve terminal?

A

An increase in presynaptic calcium concentration

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23
Q

If one would like to use the voltage clamp technique to record presynaptic calcium currents from a nerve terminal, why are tetrodotoxin (TTX) and tetraethylammonium (TEA) used?

A

TTX blocks sodium channels and TEA blocks potassium channels.

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24
Q

What is thought to significantly restrict the spread of calcium ions after they enter the nerve terminal through presynaptic calcium channels?

A

Calcium buffers and binding proteins (chelators)

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25
Q

What is the definition of a quantum of transmitter?

A

A multimolecular packet containing about 7000 transmitter molecules

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26
Q

What is the calcium sensor for synaptic vesicle exocytosis?

A

Synaptotagmin

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27
Q

What is kiss-and-run exocytosis?

A

Vesicle pore formation with the plasma membrane that is not followed by full vesicle fusion, but rather by closure of the pore

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28
Q

What is the synaptic delay at a synapse that uses chemical transmitters at room temperature?

A

0.5 miliseconds

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29
Q

What is a nanodomain of presynaptic calcium ions?

A

The collected intracellular calcium ions that form around the mouth of a single open calcium channel

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30
Q

What is the difference between an electrical synapse and a chemical synapse?

A

The electrical synapse sends current through connexons and the chemical synapse sends current through the synapctic cleft that is bridged through the release of NTs

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31
Q

What are two ways chemical transmission is possible?

A

through metabotropic receptors and ionotropic receptors

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32
Q

what are metabotropic receptors?

A

Also known as g-protein coupled receptors (GPCRs)
They are receptors about to g-proteins
they are composed of alpha, beta, and gamma subunits

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33
Q

what does the alpha do when it binds to a g-protein on a GPCR?

A

it exchanges GDP for GTP

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34
Q

what does the GCPR do at resting state?

A

it sits on the membrane and is coupled to a G protein with an alpha subunit bound to it

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35
Q

what activates a GPCR?

A

an agonist

36
Q

what happens after a GPCR is activated?

A

the alpha doesn’t want GDP anymore and instead wants to bind to GTP
so the alpha subunit and the gamma-beta subunit disassociate and leave separatly to target protein

37
Q

how does the GPCR cycle resets?

A

with GDP gone, the receptor needs alpha back to reset

38
Q
A
39
Q

How are the different G proteins classified?

A

through the different actions the do

40
Q

what ultimately decides what classification of action happens when a GPCR is activated?

A

what G-protein the alpha subunit is able to bind to

41
Q

What are the 4 G-proteins we talked about?

A

Gi, Go, Gs, Gq

42
Q

What G-protein activates PIP?

A

Gq

43
Q

What is the PI cycle?

A
44
Q

Explain the mechanism of Gi protein when it is activated

A

causes inhibition through opening of K+ channels

It inhibits the Adenylate cyclase which in turn inhibits cyclic AMP which in turn excites potassium channels to open which in turn causes inhibition of the cell

the beta-gamma subunit binds directly to K+ channels and opens them.

45
Q

Explain the mechanism of Go protein when it binds to the alpha subunit

A

it is neuron specific and acts on the presynapse
it binds to calcium channels to inhibit them, creating auto-inhibition to stop NTs release

it inhibits Ca channels (Cav2) which stops NTs release

46
Q

The use of a chemical signal that communicates from the presynaptic cell back onto the same presynaptic cell is called

A

feedback inhibition

47
Q

Explain the mechanism of Gs protein when it is activated

A

The alpha-subunit of Gs binds and activates adenylate cyclase which converts ATP into cyclic AMP which in turn acts as a second messenger to activate Kinase A which increases the phosphrylation of calcium channels, increasing their probability of opening, ultimately exciting the cell by releasing NTs

48
Q

what is Kinase A protein

A

it depends on cAMP to activate and mediates the transfer of phosphate (from ATP) to a variety of enzymes and channels

49
Q

what do Gi and Go proteins have in common?

A

they inhibit the cell it acts on

50
Q

What is cyclic AMP (cAMP)?

A

work as second messengers
- works on Gs, Gq and Gi

51
Q

what is Adenylyl cyclase?

A

an enzyme that converts ATP to cAMP

52
Q

Explain the mechanism of Gq protein when it is activated

A

Gq activates phospholipase C which catalyzes the hydrolysis of PIP2 which produces 2 second messangers
- IP3 which leaves to release calcium ions from ER and contributes to various Calcium dependent processes
-DAG remains in the membrane and activates protein kinase C which phosphorylates calcium channels to increase chances of opening them

53
Q

what channel does PIP2 regulate?

A

M-channels

54
Q

what are M-channels

A

voltage gated K+ channel that regulate the excitability of many central and peripheral neurons

55
Q

give an example of Go protein activity

A

Norepinephrine is released from neuron and it combines with the a2 receptor (an autoreceptor) which activated the Go protein
the gamma-bata subunits bind to calcium channels and inhibits them by decreasing calcium influx

56
Q

what is rectification?

A

ions flow back to membrane potential (membrane allows outward current to flow more easily than inward current)

57
Q
A
58
Q
A
59
Q
A
60
Q

what is special about the cannabinoid receptor?

A

the 2ag receptor can auto-inhibit and also inhibit inhibition

61
Q

describe some qualities of calcium

A
  • is everywhere and does a variety of things
  • presents differently at different concentration
  • intercellular concentration is low (~10x lower than extracellular concentration)
  • can be brought in through a bunch of different ways and channels
  • can be ionotropic and metabotropic
  • allows for NTs to release at synapses
62
Q

what are the 4 processes of vessicular recycling pathways?

A
63
Q

What is the kiss and run method?

A
64
Q

walk through what happens at a synapse

A
65
Q

what are 2 differences between metabotropic receptors and ionotropic receptors?

A

metabotropic receptors act through second messangers and work through g-proteins, also the work on a slower time frame
ionotropic receptors are ligand bound and act quickly

66
Q

describe 4 features of chemical synapses that allows them to have more specialization than electrical synapses

A

they can be either excitatory or inhibitory and can be activated through direct or indirect transmission

67
Q

what is reversal potential?

A

the voltage where the amount of sodium flowing in is equal to the amount of potassium flowing out
-similar to equilibrium potential

68
Q

what do indirectly coupled protein act through?

A

g-proteins

69
Q

how does glycine act as an inhibitor?

A

it makes Cl hyperpolarize signal which makes it harder to depolarize the cell and create an action potential

70
Q

why are GPCRs important?

A

they’re practically everywhere and commonly found in neurons
important to study medicine

71
Q

why are GPCRs a large part of studies in the medical field?

A

~1/3 of drugs bind to GPCRs

72
Q

how many domains is a GPCR made of and why is that important?

A

7 domains, the odd number means that one end will be on the outside while the other will be on the inside

73
Q

what is the end terminus do on GPCRs?

A

it forms the binding domain

74
Q

what binds the G-protein on the GPCRs?

A

the intercellular loops

75
Q

what does the tail do on GPCRs?

A

it can tune the phosphorylation

76
Q

what is GEF

A

gynosine exchange factor
the exchange factor can switch which form it bound on or off when it binds to a ligand

77
Q

What happens when an agonist binds to a GPCR?

A

it activates GEF which exchanged GDP for GTP and alpha subunit and gamma-beta subunit disassociate

78
Q

what would happen to metabotropic signaling in a cell if pertussis toxin is added?

A

it would irreversibly inhibit Gi and Go signaling

79
Q

what causes GPCRs to desensitize?

A

phosphorilation of the C-terminus (prime binding site located on the alpha-subunit) of the receptor

80
Q

what is the C-terminus on a GPCR?

A

the prime binding site located on the alpha-subunit

81
Q

what permits reassociation of subunits to GPCRs?

A

the alpha subunit has intrinsic GTPase activity that results in the hydrolysis of GTP back to GDP

82
Q

what terminates the activity of G proteins?

A

when the alpha subunit and the gamma-beta subunits reassociate

83
Q
A
84
Q
A
85
Q
A
86
Q
A

neurobiology (6 decks)

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