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BIPN 105 > NMJ > Flashcards

NMJ Flashcards

1
Q

What is the Neuromuscular Junction (NMJ) anatomy?

A
  • Presynaptic terminal
  • Synaptic vesicles with ACh in the presynaptic terminal
  • calcium channels on the presynaptic membrane
  • synaptic cleft
  • Postsynaptic membrane (skeletal muscle cell)
  • receptors on postsynaptic membrane for ACh
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2
Q

What kind of Ca2+ channels are on the presynaptic membrane?

A

P/Q type Ca channels

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3
Q

What is the name of the receptors on the postsynaptic membrane?

A

nmAChR- nicotinic cholinergic receptor

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4
Q

What is the postsynaptic membrane cell?

A

Skeletal muscle cell

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5
Q

How many ACh does the nmAChR require to activate?

A

2 ACh

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6
Q

What kind of cation channel is nmAChR?

A

Non-specific mixed cation channel (Na+ and K+)

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7
Q

What is the flow of Na+ and K+?

A

Na+ flows inside the cell

K+ flows outside the cell

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8
Q

What are the sizes of the force of Na+ and K+? What does it trigger?

A

Fk= very small
Fna= very large
–> nmAChR activation, Na+ influx–> depolarization

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9
Q

What is the function of NMJ?

A

Nerve AP–> muscle AP (MAP)

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10
Q

What does EPP is “graded” mean?

A

Not “all or nothing” event

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11
Q

What increases the size of EPP?

A

more ACh-> higher EPP

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12
Q

By triggering EPP, what is the result?

A

Muscle AP (MAP)

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13
Q

What are the 3 steps of Termination of an EPP?

A
  1. Stop exocytosis of ACh
  2. ACh dissociates from nmAChR
  3. ACh removed
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14
Q

How is exocytosis of ACh stopped?

A

Ca2+ diffuses away from vesicles:

[Ca2+]inside - ATPase pumps–> [Ca2+] outside

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15
Q

What happens when ACh dissociates from nmAChR?

A

nmAChR deactivates -> EPP dissipates

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16
Q

How is ACh removed?

A
  • diffuses away

- enzymatic breakdown in cleft by AChE

17
Q

What is AChE?

A

Acetylcholineesterase- breaks down ACh to choline and acetate

18
Q

What are the 2 steps of Recycling?

A
  1. Choline uptake into the presynaptic terminal

2. Choline + AcCoA – ChAT–> ACh + CoA –> ACh into vesicles

19
Q

What is ChAT?

A

choline acetyltransferase

20
Q

Draw the recycling phase

A
21
Q

How does Choline get reuptake to the presynaptic terminal?

A

By a Na+-choline cotransporter

- Na+ comes in too

22
Q

What converts choline to ACh?

A

ChAT - choline acetyltransferase

23
Q

What moves the ACh to the vesicles?

A

VAChT- vesicle ACh transporter

24
Q

What stimulates Fatigue of the presynaptic terminal?

A

High frequency nerve stimulation- depletion of ACh/vesicles

25
Q

What is Synaptic delay?

A

the delay between presynaptic depolarization and postsynaptic depolarization (EPP)

26
Q

What is the “normal” range for synaptic delay?

A

0.5-3 ms

27
Q

What is the slowest step of synaptic transmission?

A

activation of nmAChR

28
Q

What are the two mechanisms behind Facilitation?

A
  1. residual intracellular Ca2+ near presynaptic terminal membrane-> increases P/Q channel activation
  2. increased Ca2+ influx causes increased ACh release
29
Q

When does facilitation of the EPP occur?

A

When intervals of the stimulus are short enough

30
Q

Between A alpha neuron and Skeletal muscle (SKM), which has a lower Vrest?

A

SKM Resting potential= -90 mV

Aa neuron= -70mV

31
Q

Between A alpha neuron and Skeletal muscle (SKM), which has a lower Vthreshold?

A

Both are equal= -50mV

32
Q

Between A alpha neuron and Skeletal muscle (SKM), which has a longer Absolute refractory period?

A

SKM= 3-4 ms

A alpha neuron= 1ms

33
Q

Between A alpha neuron and Skeletal muscle (SKM), which has a faster conduction velocity?

A

A alpha neurone= 20-100m/s

SKM= 1 m/s

34
Q

Why is SKM slower than A alpha neuron in conduction velocity?

A

because there is no myelination

BIPN 105 (6 decks)

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