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Physiology > Motor Unit, Neuromuscular Junction, And Transmission > Flashcards

Motor Unit, Neuromuscular Junction, And Transmission Flashcards

1
Q

Each motor neuron that leaves the spinal

cord innervates?

A

many different muscle

fibers.

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2
Q

All the muscle fibers innervated
by a single motor nerve fiber are called
?

A

Motor Unit.

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3
Q

small muscles that react rapidly and need

a very fine control, have?

A

few (2-3 only)

muscle fibers in each motor unit

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4
Q

large muscles that don’t need a very fine

control, have ?

A

several hundred muscle fibers

in a motor unit

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5
Q

What’s more muscle fibers or motor neurons?

A

There are more muscle fibers in comparison to motor neurons.

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6
Q

Individual motor axons branch within muscles to synapse on many different fibers that are typically
distributed over a relatively wide area within the muscle.

Why?

A

To ensure that the contractile force of the motor unit is spread evenly.

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7
Q

reduces the chance that damage to one or a few motor neurons will significantly
alter a muscle’s action .

A

arrangement

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8
Q

action potential generated by a motor neuron normally brings to?

A

brings to threshold all of the muscle

fibers it contacts.

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9
Q

A single motor neuron and its associated muscle fibers together constitute the smallest unit of force that
can be activated to produce movement

A

MOTOR UNIT

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10
Q

Classification of Motor Unit

?

A
  1. Slow (S) motor units.
  2. Fast fatigable (FF) motor units.
  3. Fast fatigue-resistant (FR) motor units.
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11
Q

large motor neurons innervate larger, more powerful (i.e that generate
more force) motor units.

Type?

A

Fast Fatigable Motor Units

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12
Q

fibers have sparse mitochondria and are therefore easily
fatigued.
Type?

A

Fast Fatigable Motor Units

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13
Q

especially important for brief exertions that require large forces , such
as running or jumping.
Type?

A

Fast Fatigable Motor Units

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14
Q

small motor units. • In most skeletal muscles, the small motor units innervate small muscle fibers that contract slowly and
generate relatively small forces.
Type?

A

Slow Motor Units

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15
Q

because of their rich myoglobin content, plentiful mitochondria, and rich capillary beds, such
small fibers are resistant to fatigue .

A

Slow Motor Units

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16
Q

They are especially important for activities that require sustained muscular contraction. • Such as the maintenance of an upright posture.
Type?

A

Slow Motor Units

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17
Q

hey have properties that lie between those of the other two.

Type?

A

Fast Fatigue-Resistant Motor Units

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18
Q

Type?

intermediate in size and are not quite as fast as FF units.

A

Fast Fatigue-Resistant Motor Units

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19
Q

substantially more resistant to fatigue , and generate about
twice the force of a slow motor unit.
Type?

A

Fast Fatigue-Resistant Motor Units

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20
Q

Size of motor unit Contraction speed Contraction tension Mitochondrial ATPase Resistance to fatigue
Of FF

A

FF Large Fast High Low Low

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21
Q

It is the synaptic connection between the
terminal end of a motor nerve and the midpoint
of the muscle fiber.
؟

A

Neuromuscular Junction (NMJ)

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22
Q

It is the site for the transmission of action
potential from the nerve to the muscle which
travels in both directions.

A

Neuromuscular Junction (NMJ)

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23
Q

Structure of the Neuromuscular Junction

A
  1. a presynaptic part (nerve terminal,
    terminal knob), 2. the postsynaptic part (motor end plate), 3. and an area between the nerve terminal
    and motor endplate (synaptic cleft).
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24
Q

• A myelinated motor neuron, on reaching the
target muscle, loses its myelin sheath to
form a complex of 100-200 branching?

A

of 100-200 branching nerve

endings (nerve terminals) .

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25
Q

nerve terminal membrane has areas of membrane thickening called ?

A

active zones.

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26
Q 
potassium channels and
voltage-gated calcium channels on its membrane and
contains mitochondria, endoplasmic reticulum, and
synaptic vesicles (SVs).
?
A

nerve terminal

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27
Q

stores the acetylcholine (ACh), the
neurotransmitter at NMJ.
?

A

synaptic vesicles (SVs).

28
Q

The SVs are concentrated around the ?

A

active zone.

29
Q

It is the thickened portion of the muscle plasma

membrane ?

A

Postsynaptic Part (Motor End Plate)

30
Q

It is the thickened portion of the muscle plasma
membrane that is folded to form depressions
called ?

A

junctional folds.

31
Q

The terminal nerve endings do not penetrate the motor endplate but?

A

fit into the junctional folds.

32
Q

Junctional folds have ? Receptor

A

Junctional folds have nicotinic ACh receptors

concentrated at the top.

33
Q

is the space between the nerve terminal and the plasma

membrane of muscle ?

A

synaptic space or junctional cleft/ Synaptic Cleft

34
Q

is the site where presynaptic neurotransmitters, ACh is
released before it interacts with nicotinic ACh receptors on
the motor endplate?

A

Synaptic Cleft

35
Q

It contains acetylcholinesterase enzyme?

A

Synaptic Cleft

36
Q

responsible for the
catabolism of released ACh so that its effect on the post-
synaptic receptors is not prolonged.
?

A

Synaptic Cleft/ It contains acetylcholinesterase enzyme

37
Q

On arrival of an action potential at the nerve terminal in the NMJ, ?open
to cause influx.

A

Ca channels

38
Q

causes a series of events

leading to docking of about 125 SVs at active zones?

A

Increased Ca inside the nerve terminal

39
Q

exocytosis of the ACh from
the synaptic vesicles into the synaptic cleft.
?

A

Neuromuscular Transmission

40
Q

acetylcholine released from the nerve ending, it binds ?

A 
it binds to the endplate nicotinic
acetylcholine receptors (AChRs) on the postjunctional muscle membrane.
41
Q

Neuromuscular Transmission

These AChRs respond by opening channels for the ?

A

influx of sodium ions into the muscle

42
Q

These AChRs respond by opening channels for the influx of sodium ions into the muscle
leading to ?

A

endplate depolarization (end plate potential)

43
Q

• These AChRs respond by opening channels for the influx of sodium ions into the muscle
leading to endplate depolarization (end plate potential) ?

A

which initiates an action potential

at the muscle membrane causing muscle

44
Q

Activation will continue as long as?

A

Ach persists in the space (few milliseconds).

45
Q

Activation is terminated when acetylcholine is hydrolysed by ?

A

acetylcholinesterase

46
Q

the neurotransmitter used at the neuromuscular junction (works
on the nicotinic receptors). ?

A

Acetylcholine

47
Q

works

on the nicotinic receptors). ?

A

Acetylcholine

48
Q

neurotransmitter in the autonomic nervous system (primarily for the
parasympathetic nervous system-works on the muscarinic receptors). ?

A

Acetylcholine

49
Q

Acetylcholine is synthesized in the cytoplasm of the nerve terminal from ?

A

acetate and choline.

50
Q

is stored in the synaptic vesicles ?

A

Acetylcholine

51
Q

Acetylcholine It stimulates two types of receptors:?

A

muscarinic and nicotinic.

52
Q

Diseases of the neuromuscular junction can be classified as:

?

A
  1. presynaptic (e.g., Lambert-Eaton syndrome, botulism)

2. postsynaptic (e.g., myasthenia gravis).

53
Q

It is an autoimmune disease which results from antibodies that destroy nicotinic
acetylcholine receptors at the NMJ ?

A

Myasthenia Gravis

54
Q

disease can affect people of any age, it’s more common in women younger
than 40 and in men older than 60. ?

A

Myasthenia Gravis

55
Q

It causes weakness of the skeletal muscles. ?

A

Myasthenia Gravis

56
Q

Myasthenia Gravis treatment ?

A

Treatment with anticholinesterase drugs allows Ach to accumulate in the synaptic cleft.

57
Q

It is a rare autoimmune disease which results from antibodies against presynaptic voltage-gated
calcium channels in the NMJ resulting in NMJ transmission failure. ?

A

Lambert-Eaton Myasthenic Syndrome (LEMS)

58
Q

characterized by muscle weakness of the limbs.

A

Lambert-Eaton Syndrome

59
Q

LEMS have an underlying malignancy, most commonly?

A

commonly small-cell lung

cancer.

60
Q

rare and potentially fatal illness caused by a toxin produced by the
bacterium Clostridium botulinum. ?

A

Botulism

61
Q

commonly found in improperly prepared food, especially canned
vegetables or fish. also can occur as the result of a wound infection?.

A

Botulism

62
Q

acts at the neuromuscular junction to cause muscle paralysis by
preventing the exocytosis , thereby inhibiting the release of acetylcholine from
presynaptic motor neurons.
?

A

Botulinum toxin

63
Q

Drugs that stimulate the muscle fiber by Ach-like action?

A

nicotine

64
Q

Drugs that block transmission at the NMJ by competing with Ach for its
receptor?

A

curariform drugs

65
Q

Drugs that stimulate the NMJ by inactivating acetylcholinesterase?

A

neostigmine,

nerve gas).

Physiology (2 decks)

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