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BMS1052 > 8 - Synaptic Integration > Flashcards

8 - Synaptic Integration Flashcards

1
Q

Dendrites integrate info….

A

Spatially and temporally

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2
Q

Is a single presynaptic AP that produces a small EPSP sufficient to produce an AP in post-synaptic neuron?

A

No - usually insufficient

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3
Q

EPSPs associated w/ simultaneous inputs…

A

From multiple neurons sum

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4
Q

EPSPs associated w/ sequential inputs from…

A

A single neuron can sum over time

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5
Q

Will neurotransmitter be released if there’s no extracellular Ca+2?

A

No — Ca+2 influx needed to initiate presynaptic neurotransmitter release

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6
Q

Neurotransmitter vesicle release is…

A

Quantal and PSPs reflect release of many vesicles

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7
Q

Does each vesicle contain different amount of neurotransmitter?

A

No — each contain similar amount and produce similar PSP

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8
Q

Miniature PSPs

A

Voltage change due to a single vesicle

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9
Q

Why is PSP smaller at soma than at synapse?

A

Passive ion diffusion dominant in dendrites (no APs). PSP reduced in amplitude at soma due to leakage of charge in dendrites from passive diffusion.

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10
Q

What’s most important consideration about whether an AP generated?

A

Depolarisation at trigger zone

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11
Q

Trigger zone

A

Contain highest density of Nav channels and easiest place to generate an AP

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12
Q

Passive conduction in dendrites

A

EPSP decays w/ distance from synapse due to leakage of ions, reducing size of depolarisation

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13
Q

Assuming there are no voltage-gated channels…

A
  • effect of injected current decays exponentially w/ distance
  • length constant -> distance at which depolarisation decays to 1/e of max size
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14
Q

What does length constant depend on?

A
  • internal resistance (diameter, which increases towards soma)
  • membrane resistance (density open channels, which varies)
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15
Q

Do signals propagate unidirectionally in dendrites?

A

No - bidirectional

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16
Q

For PSPs of same size synapses closer to soma have greater….

A

Influence on spiking probability

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17
Q

PSP needs to reach what in order to affect spiking probability?

A

Spike initiation zone

18
Q

Active conduction always occurs in…

A

Some dendrites

19
Q

What does active conduction in dendrites depend on?

A

Voltage-gated channels, which boost membrane depolarisations

20
Q

Active conduction in dendrites improves probability that…

A

An EPSP reaches soma

21
Q

Do dendritic APs function like axonal APs?

A

No — dendritic aren’t as reliable and don’t cause as large depolarisation

22
Q

Synaptic current

A

Charge influx due to channels opening in response to neurotransmitter release

23
Q

Temporal summation is affected by…

A

Membrane time constant (how quickly it leaks charge)

24
Q

Spatial summation depends on…

A

Membrane length constant (how far charge can propagate)

25
Q

Charge leakage limits…

A

Distance over which neuron can integrate input

26
Q

Distal synapses are less effective at depolarising…

A

Soma

27
Q

Distal synapses are associated w/

A

Larger EPSPs to help counteract decay along dendrite

28
Q

Spiking threshold varies…

A

Across membrane

29
Q

What is spiking threshold determined by?

A

Minimum mempot for which an AP will occur (sufficient Nav channels need to open to initiate positive feedback)

30
Q

What’s another name for the axon hillock?

A

Trigger zone or spike initiation zone

31
Q

T/F - if Vm already at -65mV, opening more Cl channels due to influx of GABA will change Vm

A

False — because Ecl = -65mv

32
Q

Shunting inhibition

A

Inhibiting current flow from soma to axon hillock. Opening of Cl channels allows charge leakage, preventing EPSP reaching soma

33
Q

Does arrival of an AP at axon terminal guarantee vesicles will be released?

A

No - release probability < 1

34
Q

Modulating probability of vesicle release is another way to…

A

Control strength of synapse

35
Q

Pr varies between areas

A

Spinal cord motor neurons Pr = 0-1

Motor neurons Pr = 1

36
Q

Axo-axonal synapses regulate…

A

Ca+2 entry into axon terminal, modulating vesicle release

37
Q

If a 2nd AP arrives before Ca+2 in axon terminal has cleared and not all vesicles have been released in response to 1st AP,

A

2nd AP associated w/ higher intracellular Ca+2 in pre-synaptic axon terminal, greater neurotransmitter release, larger post-synaptic change

38
Q

What are autoreceptors?

A

Pre-synaptic metabotropic receptors that monitor own levels of neurotransmitter release and can inhibit neurotransmitter release and synthesis (-ve feedback)

39
Q

Neuromodulation — metabotropic

A

Some metabotropic neurotransmitters can indirectly modify size of EPSPs associated w/ other synapses

40
Q

Decreasing K+ leakage will…

A

Increase membrane resistance and length constant (makes neuron more excitable)

41
Q

Astrocytes modulate…

A

Synaptic transmission by detecting and responding to many neurotransmitters

42
Q

Back-propagation in dendrites

A

APs can travel retrogradely in dendrites

BMS1052 (10 decks)

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