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NPB 110B Exam #2 > Synaptic Plasticity > Flashcards

Synaptic Plasticity Flashcards

1
Q

Define Plasticity

A

The quality of being easily shaped or molded

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2
Q

What does synaptic plasticity do to the synapse?

A

(A) Changes in the strength of a synapse (B) changes in the size of a postsynaptic potential, in response to the same presynaptic stimulus

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3
Q

How is Synaptic plasticity caused? Hint: stimulus train

A

By repetitive action potential firing in a presynaptic cell.

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4
Q

How does Synaptic plasticity work?

A

Synaptic plasticity can work either to strengthen a synapse –increase the magnitude of the PSP -Or- to weaken a synapse -decrease the magnitude of the PSP

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5
Q

Different types of synaptic plasticity are classified by _______________.

A

how long they last

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6
Q

True or False: Changes in synaptic strength can last for different periods of time.

A

True

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7
Q

What is facilitation?

A

Short term changes a very brief increase in synaptic strength, lasting only a hundred of milliseconds (increase the magnitude of the PSP) From the textbook: an increase in PSP appears instantly and continues throughout the stimulus train.

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8
Q

What is augmentation?

A

Short term changes an increase in synaptic strength, lasting for several seconds (increase the magnitude of the PSP) A slower phase of facilitation

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9
Q

What is depression?

A

Short term change A decrease in synaptic strength, lasting several seconds (decrease magnitude of the PSP) From the textbook (TB): the decrease in PSP appears instantly and continues throughout the stimulus train a relatively long, high-frequency train of stimuli, tetanus, usually results in synaptic depression

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10
Q

What is posttetanic potentiation (PTP)?

A

Short Term change After a synaptic depression, a few seconds later, an increase in synaptic potential amplitude that can last for minutes

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11
Q

What is long term potentiation (LTP)?

A

Long Term changes an increase in synaptic strength that lasts for hours or longer (increase magnitude of the PSP) TB: Repetitive activation of synapses in the CNS can produce still more persistent changes in synaptic transmission.

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12
Q

What is long term depression (LTD)?

A

Long Term changes a decrease in synaptic strength that lasts for hours or longer.

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13
Q

The mechanism underlying all of these changes in synaptic strength all involve changes in __________ in either the presynaptic terminal or in the postsynaptic cell or both.

A

Calcium concentration

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14
Q

Choose the best option. (Facilitation/Augmentation) is the most immediate effect of PSP increase.

A

Facilitation

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15
Q

Facilitation is a ______________ due to increasing the probability of fusing and releasing NTs.

A

Presynaptic event (TB: increasing the mean number of quanta of the transmitter)

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16
Q

Why is facilitation is a presynaptic event?

A

This is due to residual calcium, leftover from previous A.P. keeps accumulating in the terminal.

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17
Q

What is a slower phase of facilitation and increase the magnitude of the PSP?

A

Augmentation, due to an increase in transmitter release

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18
Q

When is depression seen in a synapse terminal?

A

is seen when, during a train of A.P., the amplitude of the postsynaptic potential decrease.

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19
Q

Is depression a presynaptic or postsynaptic event?

A

The presynaptic event caused by release of less transmitter

20
Q

What is one factor causing depression?

A

The depletion of vesicles from the axon terminal.

21
Q

What occurs in most synapses?

A

Under physiological conditions, both facilitation and depression occur together Initially, facilitation outweighs depression and PSP gets bigger. As the train of A.P. continues, the increase in EPSP amplitude diapers facilitation weakens and depression has a stronger effect.

22
Q

What occurs in Post-tetanic potentiation (PTP)?

A

Occurs in response to tetanus (e.g. 100 A.P. per second for 15 sec, 1500 A.P. in 15 sec) takes seconds to be initiated and then it lasts for many minutes

23
Q

PTP is a ______________ due to the slow release of Ca2+ from intracellular stores like mitochondria.

A

Presynaptic cell

24
Q

True or False: During tetanus, the Na+/Ca2+ exchanger does work well due to negative membrane potential so incoming Ca2+ can be removed from the cell.

A

False

25
Q

How was Long Term Potentiation discovered?

A

In the hippocampal formation. (region of the brain known to be involved in learning and memory)

26
Q

What are homosynaptic LTP?

A

High-frequency stimulation of the perforant fiber pathway causes an increase in strength of the synapses between the pathways and cells in the dentate gyrus.

27
Q

Why is it called homosynaptic LTP?

A

Meaning that it only occurs at the synapses that received the receptive presynaptic stimulation. LTP can last for hours or even days.

28
Q

What are Associative LTP?

A

They are receptive stimulation of one input to a cell that can actually strengthen the synapse of another input to the cell.

29
Q

How do you produce an associate LTP?

Hint: Describe what is happening in the figure

A

Place two stimulating electrodes in two different parts of the Schoffer collateral pathways. Both parts of the pathway synapse onto cells in the CA1 region. Stimulus I is adjusted to provide strong input to the CA 1 region. Stimulus II is adjusted to provide weak input. The repetitive stimuli applied to electrode I produce an LTP for the synapse directly stimulated by that electrode but does not affect the synapse stimulator by electrode II. Repetitive stimulation at electrode II produces PTP at the synapse stimulated by electrode II but does not produce LTP because stimulus strength is too weak. Stimulation at both synapses at the same does produce LTP and the synapse stimulated by electrode II. –> Associate LTP

30
Q

What are the two main types of ionotropic glutamate receptors?

A

NDMA (N-methyl-D-Aspartate) AMPS (amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptor

31
Q

What are the charatertics of NDMA?

A

Blocked by Mg2+ when cell at rest MG2+ is removed from the channel pore when the cell is sufficiently depolarized by AMPA or other receptors. –> allowing Na+/Ca2+ enter PS cell after glutamate binding

32
Q

What are the charatertics of AMPA?

A

Do not have Mg2+ block Upon glutamate binding, the channel opens allowing Na+ to flow thru. It is not permeable to Ca2+

33
Q

The development of LTP is an _____________________.

A

Increase of Ca2+ in the PS cell –> only NMDAR can let Ca2+ in

34
Q

What happen when a weak stimulation is applied to the presynaptic cell? LTP

A

The AMPA receptor opens, an ESPS will occur in the PS cell, but not strong enough to remove Mg2+.

35
Q

What happen when a strong stimulation is applied to the presynaptic cell? LTP

A

The AMPA receptor opens, an ESPS will occur in the PS cell, the ESPS is strong enough to remove Mg2+, letting Ca2+ enter the cell.

36
Q

Mechanisms of Associative LTP

Choose the best option

Stimulation of (Electrode I/Electrode II) alone does not produce a large enough depolarization of PS to remove ______ from ________ receptor pores.

When activation of (Electrode I/Electrode II/both) occurs, there is a very large depolarization.

______ channels are unblocked and LTP occurs.

A

Stimulation of Electrode II alone does not produce a large enough depolarization of PS cells to remove Mg2+ from NMDA receptor pores. When activation of both electrodes occurs, there is a very large depolarization. NMDA channels are unblocked and LTP occurs.

37
Q

True or False: Both the presynaptic and postsynaptic mechanisms increase the strength of the synapse.

A

True

38
Q

What occurs in the postsynaptically and the presynaptically cells when the increase of Ca2+ activates second messenger cascades and causes?

A

(a) Postsynaptically, the PS membrane to depolarizes move in response to the same amount of NT (b) presynaptically, more NT to be released

39
Q

Where does Long Term Depression occurs?

A

Similar to LTP, same hippocampal pyramidal cells

40
Q

LTD evoked by ____________. Also require __________.

A

Low-frequency stimulation (rather than tetanus) Ca2+ influx

41
Q

What is homosynaptic LTD?

A

A prolonged weakening of synaptic strength LTD is produced by long-lasting low-frequency stimulation or by brief high-frequency stimulation of the presynaptic neuron.

42
Q

What is heterosynaptic LTD?

A

Stimulation of one synapse can cause LTD at another synapse onto the same postsynaptic cell

43
Q

What is associative LTD?

A

Combined weak and strong stimulation at two input results in depression of weakly stimulated input

44
Q

What is the mechanism of LTD?

A

LTD is also caused by an increase in Ca2+ in PS cells. (the exact mechanism are still being discovered)

(low Ca2+)

45
Q

True or False: LTD do not has an affect on both the presynaptic and postsyanpstic

A

False

NPB 110B Exam #2 (7 decks)

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