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Physiology > muscle development > Flashcards

muscle development Flashcards

1
Q

EXCITATION OF SKELETAL MUSCLE:

A

Neuromuscular Transmission and Excitation-Contraction Coupling

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2
Q

Transmission of Impulses from Nerve Endings to Skeletal Muscle Fibers:

A

The Neuromuscular Junction

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3
Q

Each nerve fiber normally stimulates 3 fibers to several hundred________

A

skeletal muscle fibers

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4
Q

The nerve ending makes a junction called the ______________, and the action potential in the muscle fiber travels in both directions toward the muscle fiber ends

A

neuromuscular
junction

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5
Q

Vesicles Containing __________are Released into the Synaptic Space

A

Acetylcholine

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6
Q

are innervated by large, myelinated nerve fibers that originate from large motoneurons in the anterior horns of the spinal cord

A

Skeletal muscle fibers

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7
Q

on the inside surface of the neuronal membranes are linear dense bars, and to the side of these bars are __________

A

voltage-gated calcium channels

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8
Q

When the action potential spreads over the nerve terminal, these
channels open, allowing __________ to diffuse into the terminal.

A

calcium ions

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9
Q

The calcium ions are believed to exert an attractive influence on
the _________vesicles, drawing them adjacent to the dense bars

A

acetylcholine

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10
Q

Some of the vesicles fuse with the neural membrane and empty
their acetylcholine into synaptic space via the process of
___________

A

exocytosis

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11
Q

In the synaptic space are large quantities of the enzyme _____________, which destroys acetylcholine a few
milliseconds after it has been released from the synaptic vesicles.

A

acetylcholinesterase

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12
Q

are located almost entirely
near the mouths of the subneural clefts lying immediately adjacent to the dense bars, where the acetylcholine is emptied into the synaptic space

A

acetylcholine-gated ion channels

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13
Q

Acetylcholine Opens Acetylcholine-Gated Ion Channels on the

A

Postsynaptic Membrane

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14
Q

The principal effect of opening the acetylcholine-gated channels
is to :

A

allow large numbers of sodium ions to move into the muscle fiber (end-plate potential)

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15
Q

Acetylcholine-gated cation channels Normally leads to opening of voltage-gated sodium channels,
which initiate an action potential at the muscle membrane,
causing _________

A

muscle contraction

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16
Q

principal effect of
opening the acetylcholine-gated channels is to allow SODIUM IONS to flow to the inside of the fiber, carrying _______ charges with
them.

A

positive

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17
Q

This action creates a local positive potential change inside the muscle fiber membrane, called the _________

A

end plate potential

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18
Q

After acetylcholine (Ach) has become attached and a
conformational change has opened the channel, allowing sodium
ions to enter the muscle fiber and excite contraction.

Note the negative charges at the channel mouth that prevent passage of
negative ions such as ________ions.

A

chloride

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19
Q

This end plate potential normally causes sufficient depolarization
to open neighboring __________, allowing
even greater sodium ion inflow and initiating an action potential
that spreads along the muscle membrane and causes muscle
contraction.

A

voltage-gated sodium channels

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20
Q

Acetylcholine Released into the Synaptic Space is Destroyed by
___________ or Simply Diffuses Away

A

Acetylcholinesterase

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21
Q

acetylcholine, once released into the synaptic space,
continues to activate the ___________ for as long as it
remains in the space

A

acetylcholine receptors

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22
Q

Most of the acetylcholine is destroyed by the enzyme
__________

A

acetylcholinesterase

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23
Q

The short period during which the acetylcholine remains in the synaptic
space – a ____________ at most – is always sufficient to excite the muscle fiber under normal conditions.

A

few milliseconds

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24
Q

Acetylcholinesterase is attached mainly to the spongy layer of fine connective tissue that fills the synaptic space between the ___________ & ____________

A

presynaptic nerve terminal

postsynaptic muscle
membrane.

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25
Q

Then the rapid removal of the ____________ prevents continued muscle re-excitation after the muscle fiber has recovered from its
initial action potential.

A

acetylcholine

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26
Q

Acetylcholine Produces an End-Plate Potential that Excites the
_________

A

Skeletal Muscle Fiber

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27
Q

The sudden insurgence of sodium ions into the muscle fiber when the acetylcholine-gated channels open causes the electrical potential inside the fiber at the local area of the end plate to increase in the positive direction as much as ______________,
creating a local potential called the end plate potential.

A

50 to 75 millivolts

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28
Q

The end plate potential created by acetylcholine stimulation is
normally far ________that necessary to initiate an action potential in the muscle fiber.

A

greater than

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29
Q

The weakness of the end plate potential at point C resulted from
the effect of ________

A

botulinum toxin

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30
Q

a bacterial poison that decreases the quantity of acetylcholine released by the nerve terminals

A

botulinum toxin

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31
Q

Drugs can Affect the Neuromuscular Junction by having
____, _____, & ____

A

Acetylcholine-Like Actions,

Blocking Neuromuscular Transmission,

Inactivating Acetylcholinesterase

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32
Q

Medication that stimulates drugs that have acetylcholine-like
actions:

A

methacholine,
carbachol,
nicotine

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33
Q

have the same effect on the muscle fiber as does
acetylcholine.

The only difference is that these drugs are not
destroyed or can only be slowly removed by
___________, unlike acetylcholine.

A

cholinesterase

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34
Q

Drugs that block neuromuscular transmission.

A

curariform drugs

ex. tubocurarine

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35
Q

prevent passage of impulses from the end plate into the muscle.

A

curariform drugs

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36
Q

can cause PARALYSIS , classic example is ___________which competes with acetylcholine for
the site, hence, affecting your membrane.

The acetylcholine cannot increase permeability to the
muscle membrane and acetylcholine channels
sufficiently initiates an action potential.

A

tubocurarine

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37
Q

Drugs that inactivate acetylcholinesterase. Three particularly
well-known drugs –

A

neostigmine
physostigmine
diisopropyl fluorophosphate

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38
Q

These will inactivate acetylcholinesterase so that
acetylcholine effect is prolonged, as a result this will increase levels of acetylcholine with successive nerve
impulses causing large amounts of acetylcholine to
accumulate and repetitively stimulate the muscle fiber

A

Drugs that inactivate acetylcholinesterase

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39
Q

potentially last for several hours, thereby allowing
acetylcholine to accumulate in the synaptic space

A

neostigmine and physostigmine

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40
Q

used as a nerve gas poison because the effect of
preventing acetylcholinesterase is longer (recorded to
be weeks, and is very dangerous)

A

Diisopropyl fluorophosphates

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41
Q

causes muscle paralysis.

Paralysis occurs because of the inability of the
neuromuscular junctions to transmit signals from the
nerve fibers to muscle fibers.

A

Myasthenia Gravis

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42
Q

Pathologically,
is thought to be an
autoimmune disease in which patients have developed
antibodies against their own acetylcholine-gated ion
channels.

The end-plate potential that occurs in the muscle fiber
is going to be weak to initiate any voltage-gated sodium channel, thus, the polarization will not occur

An antibody attacks the acetylcholine gated ion
channels on the muscular site, causing weakness to the point of paralysis

A

myasthenia gravis

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43
Q

If the disease is sufficiently advanced, the patient can
die of paralysis (paralysis of the respiratory muscles e.g.
diaphragm).

A

myasthenia gravis

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44
Q

myasthenia gravis can be ameliorated by giving _____________
Mu(anti-cholinesterase) which prevents the
destruction of acetylcholine.

A

neostigmine

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45
Q

This will result in the
accumulation/high levels of acetylcholine in the
synaptic cleft.

A

neostigmine against myasthenia gravis

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46
Q

The resting membrane potential is about ________ in skeletal muscle fibers, which is similar to that of large, myelinated nerve fibers which innervates the skeletal muscles

A

-80 to -90 millivolts

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47
Q

The duration of the action potential is only 1 to 5 milliseconds in the skeletal muscles which is ________ than in large,
myelinated nerve fibers.

A

five times longer

48
Q

Myelination increases velocity

The velocity of conduction is 3 to 5 m/sec in skeletal
muscle, which is about _________ the velocity of conduction
in the large myelinated nerve fibers that excite skeletal muscle

A

1/18

49
Q

Muscles eventually develop ______
which are important for the excitation contraction coupling.

Are internal extensions of the cell membrane.

A

Transverse Tubules (T Tubules)

50
Q

run transverse to the myofibrils and begin at
the cell membrane of the muscle and penetrate from
one side of the muscle to the opposite side.

A

T tubules

51
Q

internal extensions of the cell membrane,

when an action potential spreads over a muscle fiber
membrane, it also spreads along the T tubules to the interior of the muscle fiber

A

T tubules

52
Q

Is Composed of Longitudinal Tubules and
Terminal Cisternae

A

Sarcoplasmic Reticulum

53
Q

_________ of the sarcoplasmic reticulum run
parallel to the myofibrils and terminate in large chambers called
terminal cisternae

A

longitudinal tubules

54
Q

In cardiac muscle, a single T tubule network for each sarcomere is located at the level of the

A

Z disk

55
Q

In mammalian skeletal muscle, there are _______ T tubule networks
for each sarcomere located near the two ends of the myosin filaments, which are the points at which the mechanical forces of
muscle contraction are created.

A

2

56
Q

Calcium lons Are Released From the __________ of the Sarcoplasmic Reticulum

A

Terminal Cisternae

57
Q

From the nerve: post synaptic cleft of the muscle
membrane, goes to the T tubules, then T tubules
coordinate with the _________

A

terminal cisternae

58
Q

After the contraction, a __________assists the removal of the
calcium ions to go back into the sarcoplasmic reticulum

A

Calcium pump

59
Q

A continually active calcium pump located in the walls of the ___________ of the sarcoplasmic reticulum

pumps calcium ions AWAY from the myofibrils,

BACK into the SARCOPLASMIC TUBULES

A

longitudinal tubules

60
Q

The pump can concentrate the calcium ions to about
__________ inside the tubules

A

10,000 fold

61
Q

inside the
reticulum is a calcium-binding protein called

This protein can provide another 40 fold
increase in storage of calcium inside the
reticulum.

A

Calsequestrin

62
Q

This transfer of calcium into the sarcoplasmic reticulum depletes calcium ions in the sarcoplasmic fluid, thereby _________

A

terminating the
muscle contraction

63
Q

refers to the conversion of
action potential into a mechanical muscle contraction.

It is a process that happens in your muscles when you want to move.

A

Excitation Contraction coupling

64
Q

The activation of a nerve, specifically a motor neuron.

Your brain sends a signal to your muscles, telling them to contract (get shorter and
tighter). This signal travels through your nerves like an
electrical message.

A

Excitation

65
Q

The interaction (i.e. shortening) that
takes place between the actin and myosin filaments of the sarcomere.

Calcium is like a key that unlocks your muscle fibers, allowing them to shorten and contract.

Think of it as TURNING ON a switch that makes your
muscles work

A

Contraction

66
Q

Lead to muscle action. When the electrical message reaches your muscle fibers, it needs to make them contract.

It does this by causing tiny storage units
in your muscles, called “calcium storage units,” to
release calcium

A

Coupling

67
Q

calcium storage units

A

Coupling

68
Q

At the beginning of this process, the sarcomere and/or muscle fiber is in a ___________.

Where there is just minimal overlap
of actin and myosin filaments.

A

resting position

69
Q

Because communication is needed between the nervous and muscular systems, in order for contraction to occur, it makes
sense that there is a MEETING PLACE called the ____________for these systems to actually communicate

A

Neuromuscular
Junction

70
Q

participants of neuro muscular junction:

A

motor neuron
synaptic terminal
motor end plate
synaptic cleft
sarcomere
synaptic vesicles
sarcoplasmic reticulum

71
Q

nerve that connects to and powers the muscle fiber

A

motor neuron

72
Q

represents the end component of the motor neuron

A

synaptic terminal

73
Q

area that represents the part of muscle fiber in which the motor neuron sits

A

motor end plate

74
Q

space between the synaptic terminal and end plate

A

synaptic cleft

75
Q

travel along the axons of neurons and reach the synaptic terminal

A

action potential

76
Q

release neurotransmitters called acetylcholine

A

synaptic vesicles

77
Q

a receptor, where the acetylcholine binds in the motor end plate

A

nicotinic acetylcholine receptor

78
Q

sodium begins to enter the muscle fiber, potassium leaves

more sodium enter, less K+ leaving 3:2

A

activation of sodium-potassium pump

79
Q

action potential travels now in __________

initiating calcium from sarcoplasmic reticulum into sarcoplasm

A

t-tubules

80
Q

muscle cell is also referred to as a

A

muscle fiber

81
Q

Muscle cell membrane

A

Sarcolemma:

82
Q

Muscle cell cytoplasm

A

Sarcoplasm

83
Q

Muscle cell smooth endoplasmic
reticulum (SER)

A

Sarcoplasmic reticulum

84
Q

the presence of these cells is a great issue
with the muscles because skeletal muscles have limited ability to proliferate and differentiate into muscle cells and
as a result, sometimes extensive injury to your muscles
would result into muscles not being fully repaired.

It is because it has very limited capacity to
regenerate

A

Satellite cells –

85
Q

induce skeletal muscle
hypertrophy rather than hyperplasia

A

Muscle-building exercises

86
Q

if you go further, it is a dense connective tissue
that surrounds each muscle fiber

A

Epimysium

87
Q

contractile unit of your muscle

A

Sarcomere

88
Q

has the capacity to regenerate

lots of tumors

A

smooth muscle

89
Q

thin and long bundles that fill the muscle fibers
for each muscle fiber

A

myofibril

90
Q

is the direct invagination of the muscle membrane
that terminally bathing the cisternae of sarcoplasmic reticulum
and it is quite important for your Calcium

A

T-tubules

91
Q

less dark band with only thick filaments

middle portion of the A band

A

H band

92
Q

faint line that anchors the thick filaments

midline of the A band

A

M line

93
Q

light band

area with only thin filaments

loc. at lateral portions spanning 2 sarcomeres

A

I band

94
Q

middle of I band

anchor thin filaments and mark the boundary of or sarcomeres

loc. at end margin of sarcomere, midline of I band

A

Z line (Z disc)

95
Q

If you damage a motor neuron (that 3 to
several hundreds of muscular fibers)

and
there is no innervation of muscle there could be _______of
several groups of muscles.

A

atrophy

96
Q

group of skeletal muscle fibers innervated by a single motor neuron that contracts together

A

motor unit

97
Q

motor units:

A

large motor unit
small motor unit

98
Q

large group of motor fibers innervated by a single motor neuron that typically generate a large contractile force but is relatively slow to respond as a whole

ex. muscles of posture that supports your back, thighs and buttocks

A

large motor unit

99
Q

group of motor fibers innervated by a single motor neuron necessary for very DELICATE & FAST MOVEMENT

ex. muscles of the eyes, muscles of the fingers of the hands

A

small motor unit

100
Q

3 types of skeletal muscles

A

type 1 (red, slow-twitch) fibers

type 2a (intermediate fibers)

type 2b (white, fast-twitch) fibers)

101
Q

Small diameter; red appearance due to high
myoglobin content;
many mitochondria

Slow to contract but
resistant to fatigue;
undergo oxidative phosphorylation to produce maximum ATP

Postural muscles; large amount in muscles of endurance athletes

A

type 1 (red, slow-twitch) fibers

102
Q

Medium-sized diameter;
slightly red due to good
amount of myoglobin;
many mitochondria;
glycogen storage

Faster to contract and
fairly resistant to fatigue;
generate ATP by both oxidative phosphorylation
and glycolysis

Large amount in mid-distance runners and swimmers

A

Type 2a (intermediate) fiber

103
Q

Large diameter; light pink due to less myoglobin;
fewer mitochondria;
large glycogen storage

Fast to contract and prone
to fatigue; generate
ATP rapidly by anaerobic
glycolysis. Lactic acid by-products cause fatigue

Extraocular muscles,
muscles of the fingers;
large amount in short-distance runners and weight lifters

A

Type 2b (white, fast-twitch) fibers

104
Q

are like tortoise: Slow moving but steady, and they
take first place

A

Type I fibers

105
Q

are like the hare: Fast but Resting in the middle,
and they come in last place

A

Type 2b fibers

106
Q

are between the other two, chronologically.

They
come in the middle and, hence, are intermediate fibers

A

Type 2a fibers

107
Q

Usually the result at the time of death.

the dead body becomes rigid because the calcium leaks out and into the sarcolemma, and this causes actin and myosin
interaction, but due to a lack of developing ATP, the interaction cannot be separated. This results in MUSCLE RIGIDITY. Remember,
you need ATP also for muscle relaxation

A

Rigor mortis

108
Q

Decrease in muscle cell volume with the loss of
myofibrils as the result of inactivity or loss of motor innervation

A

Atrophy

109
Q

Episodic and progressive muscle weakness commonly as the result of autoimmune antibody binding and
blocking acetylcholine receptors at the neuromuscular junctions

A

Myasthenia gravis

110
Q

often short with a single, oval Nuclei but they
have their own striations. They also store some form of glycogen

and what is characteristic is the presence of Intercalated disc, which are necessary to create a syncytium – that allows for
immediate transfer of action potential and stimulus.

A

cardiac muscleS

111
Q

transverse portion of
the adhesion junctions and the lateral portion of the gap junctions

AND 1 terminal cisternae and T-tubules named______

A

DIAD

112
Q

in sarcoplasmic reticulum of skeletal muscle, 2 T-tubules and cisternae

A

TRIAD

113
Q

Injury and cell death at a region of the heart as a result of poor or blocked blood supply. Injured area s
replaced by scar tissue rather than new cardiac cells due to their inability to proliferate

A

Myocardial infarction (MI)

114
Q

Benign smooth muscle tumors often arising in the
uterus; the most common neoplasm in women

A

Leiomyoma

115
Q

Malignant smooth muscle tumors; 10% to 20%
of soft tissue tumors

A

Leiomyosarcoma

Physiology (11 decks)

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