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Neurobio > Neurobio 2.6 > Flashcards

Neurobio 2.6 Flashcards

1
Q

Method used in first experiment suggesting presence of vesicles.

A

Bernard Katz recorded from endplate of frog neuromuscular junction w/o any stimulation.

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2
Q

What did Katz observe?

A

Spontaneous mini EPPs (minis) at regular intervals. Usually 1 mv, but sometimes ones two or three times larger.

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3
Q

Size of a mini in a frog neuromuscular junctino

A

0.7 mV

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4
Q

Typical duration of mini

A

10ms

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5
Q

Quanta

A

Packets of neurotransmitters

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6
Q

Each quantum produces

A

1 mini

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7
Q

According to quantum hypothesis, a full size EPP occurs when

A

an action potential causes the synchronous release of many quanta

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8
Q

Quantum size

A

Size of a mini

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9
Q

Quantum size of most central synapses

A

0.1-0.2 mV

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10
Q

Quantum content

A

number of packets (quantums) released due to an action potential

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11
Q

Quantum content at neuromuscular junction

A

About 200

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12
Q

Quantum content in CNS

A

between zero and 2

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13
Q

Physical correlates of quantums are

A

vesicles

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14
Q

Why is an AP in muscle cells guaranteed to generate a response?

A

Quantum number is so high

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15
Q

Places vesicles might be found in presynaptic terminal

A
  1. Readily releasable pool

2. Storage pool

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16
Q

Tends to be anchored to cytoskeleton

A

storage pool

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17
Q

Docked at active zones of presynaptic terminal

A

Readily releasable pool

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18
Q

Anchors vesicles to cytoskeleton

A

Synapsin I

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19
Q

Synapsin I is located

A

in vesicle membrane

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20
Q

Effect of calcium on synapsin I

A

interaction between vesicles and cytoskelton becomes weaker, freeing vesicles

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21
Q

Two proteins calcium binds upon entering terminal of presynaptic cell

A 
Synapsin I (storage pool)
Synaptotagmin I (readily releasable pool)
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22
Q

Two effects of calcium entering terminals of presynaptic cell

A

Readily releasable vesicles released and storage pool vesicles mobilized

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23
Q

Function of the SNARE complex

A

Docking of vesicles at active zone of presynaptic membrane.

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24
Q

How calcium relates to SNARE complex

A

Binds synaptotagmin I on vesicle. Somehow the membranes of vesicle and presynaptic terminal active zone then fuse together.

25
Q

Where are the alpha helices of the SNARE complex?

A

Protrude into cytoplasm.

26
Q

Describe SNARE complex

A

Synaptobrevin alpha helix protrudes from vesicle. SNAP-25 and and syntaxin alpha helices protrude from presynaptic membrane. The alpha helices are like velcro.
Synaptotagmin I is on the vesicle.

27
Q

VSNARE

A

synaptobrevin (on vesicle)

28
Q

TSNARE

A

Syntaxin and SNAP-25 (targets of vesicle fusion)

29
Q

Why is curare useful in studying neuromuscular junction?

A

Competitive inhibitor of acetyl choline which prevents action potential but not end plate potential. Now you can study end plate potential alone and without the muscle moving.

30
Q

Some bacterial toxins that target SNARE

A

Tetanus toxin

Botulinum toxin A and C

31
Q

How toxins that target SNARE work (how are they classified)

A

Proteases that hydrolyze the proteins

32
Q

Tetanus toxin targets

A

synaptobrevin

33
Q

Targets SNAP-25

A

Botulinum toxin A

A = apple = SNAPple

34
Q

Targets syntaxin

A

Botulinum toxin C

C for Syn

35
Q

Calcium pump takes about _____

A

100 ms

This is the time needed for calcium in presynaptic cells to return to normal calcium levels

36
Q

Clears away calcium after AP causes entry into presynaptic cell

A

calcium pumps

37
Q

Two types of synaptic plasticity

A
  1. Paired pulse facilitation

2. LTP (long term potentiation)

38
Q

How paired pulse facilitation works

A

When AP’s are fired in succession, residual calcium from previous AP’s causes increase in amplitude of next EPSP’s

39
Q

Short term synaptic plasticity

A

Paired pulse

40
Q

Neurons thought responsible for long-term memory

A

CA1 and CA3 neurons of the hippocampus

41
Q

100 Hz corresponds to ____ interval between pulses

A

10ms

42
Q

Result of one tetanus stimulation

A

The second AP generates EPSP up to three times larger. After first 1/2 hour, EPSP is larger but not as much, goes down after about another 1/2 hour, and after about 2 hours, decays back to normal.

43
Q

Result of four tetanus stimulations

A

EPSP elevation lasts for up to 10 hours

44
Q

Early LTP

A

One tetanus stimulation

45
Q

Late LTP

A

Multiple (four was example given in class) trains of tetanus stimulations

46
Q

Two glutamate receptors on post-synaptic membrane involved in LTP are:

A

AMPA

NMDA

47
Q

Two phases of LTP

A
  1. Induction phase

2. Expression phase

48
Q

What happens during induction phase of LTP?

A
  1. Tetanus causes summation of EPSP’s
  2. Sustained depolarization removes magnesium block from from NMDA receptors
  3. NMDA conducts calcium through post-synaptic membrane and so both AMPA and NMDA receptors are bringing in calcium
49
Q

What happens during expression phase of LTP?

A

Three mechanisms are involved

  1. Ca increase activates calmodulin, which activates CaM kinase II, which phosphorylates AMPAR’s, causing them to generate a larger inward current.
  2. CaM kinase II somehow causes vesicles whose membranes contain AMPAR’s to fuse with post-synaptic membrane
  3. Activation of silent synapses
50
Q

How are silent synapses activated during LTP?

A

At first, they have no AMPA receptors on membrane. Depolarization from neighboring synapses is strong enough to remove magnesium block from NMDA. Calcium enters and, through insertion mechanism, AMPA receptors are inserted into membrane.

51
Q

Two properties of LTP

A

Cooperativity and associativity

52
Q

Cooperativity

A

Many CA3 neurons must be activated in order for the spatial summation of PSP’s to be strong enough to remove magnesium block from NMDAr’s.

53
Q

Associativtity

A

Both pre and post-synaptic neurons must be activate at same time: pre for generating depolarization, and post-synaptic for NMDA magnesium block to get removed

54
Q

Cooperativity and associativity are due to teh special properties of

A

NMDA receptors

55
Q

Following LTP, longer term changes include

A

transcription of new proteins and formation of new synapses

56
Q

Describe a “repetitive” stimulation of CA3

A

100 stimulates pulses at 100Hz (10ms between pulses)

57
Q

Stimulus artifact

A

Recorded by electrode in bath which contains the cell (not a direct biological response)

58
Q

How expression phase relates to IV curve equation

A

Increases Po and N

I = N * Po * gamma * (Vm-Erev)

59
Q

After first of paired-pulse facilitation, Ca++ levels stay elevated about

A

20-100ms

Neurobio (31 decks)

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