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E-lfh FRCA Primary: Pharmacology - Muscle Relaxants > The Neuromuscular Junction and The Nicotinic Acetylcholine Receptor > Flashcards

The Neuromuscular Junction and The Nicotinic Acetylcholine Receptor Flashcards

1
Q

What is the diameter of an alpha motor fibre?

A

10 micrometers

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2
Q

What is the speed of conduction down an alpha motor fibres?

A

50-100 m/s

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3
Q

Regarding Acetylcholine (true of false):

Acetylcholine is synthesised in α-motor neurons

A

True.

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4
Q

Regarding Acetylcholine (true of false):

Acetylcholine contains a tertiary amine group

A

False. Acetylcholine contains a quaternary ammonium ion.

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5
Q

Regarding Acetylcholine (true of false):

Choline is an essential amino acid

A

False. Choline is an essential nutrient but not an amino acid.

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6
Q

Regarding Acetylcholine (true of false):

Acetylcholine requires oxidative phosphorylation of pyruvate for its precursor acetyl-CoA

A

False. Acetyl-CoA is formed from oxidative decarboxylation of pyruvate.

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7
Q

Regarding Acetylcholine (true of false):

Acetylcholine contains a single ester linkage

A

True

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8
Q

During neuromuscular transmission (true or false):

Motor nerves conduct at 5-10 m/s

A

False. Motor neurones conduct faster than this at 50-100 m/sec.

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8
Q

During neuromuscular transmission (true or false):

Nodes of Ranvier contain ligand-gated ionic channels

A

False. There are voltage-gated ion channels at the nodes of Ranvier.

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9
Q

During neuromuscular transmission (true or false):

Schwann cells provide insulation of the nerve fibre

A

True

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10
Q

During neuromuscular transmission (true or false):

Saltatory conduction involves the opening of sodium channels

A

True

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11
Q

During neuromuscular transmission (true or false):

NAChRs are present in the clefts of the post-synaptic membrane

A

False. The nicotinic receptors are on the shoulder and crests of the post-synaptic membrane.

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12
Q

Regarding presynaptic motor nerve terminals at the NMJ (true or false):

Ligand-gated calcium channels regulate vesicle exocytosis

A

False. Voltage-gated calcium channels mediate vesicle release.

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13
Q

Regarding presynaptic motor nerve terminals at the NMJ (true or false):

ACh provides presynaptic feedback-inhibition

A

False. ACh mediates increased release of ACh presynaptically.

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13
Q

Regarding presynaptic motor nerve terminals at the NMJ (true or false):

L-type calcium channels are found presynaptically at the NMJ

A

False. N-type calcium channels are present presynaptically at the NMJ.

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14
Q

Regarding presynaptic motor nerve terminals at the NMJ (true or false):

NAChRs are found presynaptically

A

True

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15
Q

Regarding presynaptic motor nerve terminals at the NMJ (true or false):

In Lambert-Eaton syndrome, there are antibodies against presynaptic calcium channels

16
Q

At the post-synaptic membrane of the NMJ (true or false):

AChE is found in the clefts of the folded membrane

17
Q

At the post-synaptic membrane of the NMJ (true or false):

Individual AChE molecules are free in the synaptic cleft

A

False. AChE tends to form clusters and is loosely anchored to the membrane.

18
Q

At the post-synaptic membrane of the NMJ (true or false):

NAChR have four different types of subunit

A

True. NAChR has five subunits, but two α subunits.

19
Q

At the post-synaptic membrane of the NMJ (true or false):

ACh binds to the β subunit of the nicotinic receptor

A

False. ACh binds to the α subunits.

20
Q

At the post-synaptic membrane of the NMJ (true or false):

Only sodium ions pass through the opened ion channel

A

False. Potassium ions can also pass through, but move outward.

21
Q

Regarding the motor endplate (true or false):

The resting potential of skeletal muscle is -70 mV

A

False. The resting potential of skeletal muscle is between -90 mV and -85 mV. -70mV is the threshold for voltage-gated sodium channels to open.

22
Q

Regarding the motor endplate (true or false):

MEPPs reflect spontaneous release of ACh

23
Q

Regarding the motor endplate (true or false):

Current flow through a single ion channel is around 50 pA

A

False. Current flow through a single ion channel is around 5 pA

24
Q

Regarding the motor endplate (true or false):

The Nernst potential for sodium is -50 mV

A

False. The Nernst potential for sodium is around +50 mV.

25
Q

Regarding the motor endplate (true or false):

The muscle depolarises when the EPP reaches +15 mV

A

False. Muscle depolarises when the EPP reaches the threshold for voltage-gated sodium channels to open, around -70 mV.

26
Q

Pre-synaptically at the NMJ (true or false):

Calcium entry is essential for vesicle exocytosis

27
Q

Pre-synaptically at the NMJ (true or false):

SNARE proteins provide the mechanism for membrane fusion

28
Q

Pre-synaptically at the NMJ (true or false):

Nicotinic receptors have the same subunit composition as at the autonomic ganglia

A

False. Nicotinic receptors and autonomic ganglia have different types of α and β subunits.

29
Q

Pre-synaptically at the NMJ (true or false):

The calcium channel is of the same type as found in myocardial muscle

A

False. T-type and L-type calcium channels are found in cardiac muscle and N-type pre-synaptically.

30
Q

Pre-synaptically at the NMJ (true or false):

All vesicles are anchored to the presynaptic membrane

A

False. Some vesicles are attached awaiting release, but some are free in the cytoplasm.

31
Q

The muscle membrane has (true or false):

Ligand-gated sodium channels that depolarise when the EPP is reached

A

False. Voltage-gated sodium channels are responsible for depolarisation when the endplate potential is reached.

32
Q

The muscle membrane has (true or false):

T-tubules that fold into the cell

33
Q

The muscle membrane has (true or false):

L-type voltage-gated calcium channels in the T-tubules

34
Q

The muscle membrane has (true or false):

Ryanodine RyR2 receptors

A

False. Ryanodine RyR1 receptors are in the membrane of the sarcoplasmic reticulum; RyR2 are found in myocardial cells.

35
Q

The muscle membrane has (true or false):

Voltage-gated calcium channels with pore-forming domains in the α1 subunit

36
Q

At the NMJ (true or false):

ACh acts exclusively through nicotinic receptors

37
Q

At the NMJ (true or false):

Neostigmine is a competitive inhibitor at nicotinic receptors

A

False. Neostigmine inhibits AChE.

38
Q

At the NMJ (true or false):

Nicotine causes receptor up-regulation

A

False. Nicotine causes down-regulation of receptors.

39
Q

At the NMJ (true or false):

Plasma cholinesterase is present in the synaptic cleft

A

False. Plasma cholinesterase is not present at all.

40
Q

At the NMJ (true or false):

Organophosphates increase ACh levels in the synaptic cleft

A

True. Organophosphates increase ACh levels in the synaptic cleft and lead to flaccid paralysis.

E-lfh FRCA Primary: Pharmacology - Muscle Relaxants (7 decks)

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