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M2M Unit IV > Muscle > Flashcards

Muscle Flashcards

1
Q

In the relaxed state, the binding of myosin to actin is prevented because the binding site on actin is covered by _______.

A

tropomyosin

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1
Q

Dystrophin links the _____ with the _____.

A

cytoskeleton; extracellular matrix

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1
Q

The _____ is located in the t-tubule membrane.

A

DHPR (dihydropyridine receptor)

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2
Q

Single amino acid mutations in the regulatory regions of a _____ or a _____ produce muscle disease.

A

myofilament protein; regulatory protein

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3
Q

Striations results from the ______ in precise register across the width of the myofiber.

A

stacking of sarcomeres

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3
Q

At the Z line, _____ is a molecule that crosslinks actin filaments.

A

alpha-actinin

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4
Q

Increased calcium in the _____ cell binds to calmodulin and the Ca-calmodulin binds to CaM kinase and activates it so that one of the light chains on the _____ is phosphorylated.

A

smooth muscle; myosin head

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4
Q

As you exercise, more _____ are added and the muscle fibers get larger.

A

myofilaments

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5
Q

What is a muscle cell stem cell called?

A

satellite cells

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6
Q

Transmission of the action potential to the interior occurs via the ______ membrane.

A

transverse tubule (t-tubule)

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6
Q

Cardiac and smooth muscle can function without _____.

A

nervous innervation

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6
Q

How can cardiac and smooth muscle tension be graded?

A

1) neurotransmitters 2) hormone-like molecules 3) cell length

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7
Q

Bound to the actin filaments are two important regulatory proteins, _____ and ______.

A

tropomyosin; troponin

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7
Q

_____ links the cytoskeleton with the extracellular matrix.

A

Dystrophin

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7
Q

Depolarization of a muscle cell will open Na channels and an _____ is initiated.

A

action potential

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8
Q

A muscle cell is called a _____.

A

myofiber

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10
Q

The ______ is the connective tissue within the fascicles that surrounds and invests the muscle cells.

A

endomysium

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11
Q

The ______ is in the SR membrane and is a Ca release channel.

A

RyR (ryanodine receptor)

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12
Q

The ______ surrounds the fascicles.

A

perimysium

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12
Q

Where are the nuclei located in skeletal muscle cells?

A

in the periphery

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13
Q

The majority of people with _____ have mutations in the cardiac myosin heavy chain

A

FHC

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14
Q

Dantrolene blocks muscle contraction by blocking ____ release from the SR.

A

Ca+2

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15
Q

A fascicle is a ______.

A

bundle of muscle cells

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15
Q

______ causes a conformational change in the DHP receptor that in turn causes the calcium release channel to open and Ca flows out of the SR.

A

Depolarization

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16
Q

The endomysium is the connective tissue within the fascicles that ______.

A

surrounds and invests the muscle cells

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18
Q

How many nuclei does a skeletal muscle cell have?

A

many- can be several hundred

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19
Q

Both cardiac and smooth muscle cells are linked by ______.

A

gap junctions

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20
Q

About half of all cases of sudden death due to cardiac arrest in young athletes are due to ______.

A

familial hypertrophic cardiomyopathy (FHC).

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21
Q

The shortening of the sarcomere is about ____.

A

8 nm

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22
Q

Increased _____ in the smooth muscle cell binds to calmodulin, and the Ca-calmodulin binds to _____ and activates it so that one of the light chains on the myosin head is phosphorylated.

A

calcium; CaM kinase

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22
Q

In MH, the steady Ca+2 leak from the SR activates the _____ to pump Ca+2 back into the SR and a futile, heat-producing cycle occurs and is lethal if not corrected.

A

Ca+2 ATPase

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23
Q

In smooth muscle, removal of Ca is accomplished by ____ and _____ in the sarcolemma.

A

Ca pumps; Na-Ca exchangers

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23
Q

What is the incidence rate of MH?

A

1:15,000

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24
Q

_____ contains no troponin, but calcium is still the key regulatory molecule.

A

Smooth muscle

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24
Q

The DHPR (dihydropyridine receptor) is located in the ______.

A

t-tubule membrane

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25
Q

What does FHC stand for?

A

familial hypertrophic cardiomyopathy

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26
Q

Transmission of the action potential to the ____ occurs via the transverse tubule (t-tubule) membrane.

A

interior

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27
Q

Small motor units are recruited _____ and progressively larger motor units are _____ as the strength of contraction is increased.

A

first; recruited

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28
Q

Smooth muscle cells are so thin that Ca+2 entering via Ca+2 channels in the surface membrane can easily ______.

A

diffuse to the center of the cell

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30
Q

_____ makes up the thin filaments.

A

F-actin

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30
Q

The myosin in fast twitch muscle cycles about ____ times per second.

A

20

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31
Q

One of the subunits of the DHP receptor is a _____; the other molecule is the RyR (ryanodine receptor).

A

voltage-gated Ca channel

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32
Q

Fibroblasts prevent the premature differentiation of _____.

A

satellite cells

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33
Q

Each _____ is wrapped in its own SR.

A

myofibril

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33
Q

Depolarization causes a conformational change in the _____ that in turn causes the calcium release channel to open and Ca flows out of the SR.

A

DHP receptor

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33
Q

An abnormal calcium release channel in the SR causes a disease called _______.

A

malignant hyperthermia (MH)

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33
Q

What does MH stand for?

A

malignant hyperthermia

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34
Q

______ can repair itself; the cells can dedifferentiate, enter mitosis, and regenerate new muscle cells.

A

Smooth muscle

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35
Q

As strength increases, the cross sectional area of each cell is increased; new ______ are formed.

A

myofibrils

36
Q

The thick filaments are_____ long and contain 300-400 myosins.

A

1.6 micrometers

36
Q

_____ are recruited first and progressively _____ are recruited as the strength of contraction is increased.

A

Small motor units; larger motor units

38
Q

Binding of _____ allows myosin to dissociate from actin.

A

ATP

39
Q

What is the triad?

A

apposition of the SR and the t-tubule that looks dark in microscopy

40
Q

The AChR is an _____ that opens and causes depolarization.

A

ion channel

41
Q

In normal, relaxed muscle [Ca]i is _____.

A

low (

42
Q

Muscles that ______ tend to have small motor units while large muscles that make _____ have large motor units.

A

perform fine movements; gross movements

43
Q

______ in the regulatory regions of a myofilament protein or a regulatory protein produce muscle disease.

A

Single amino acid mutations

44
Q

Calsequestrin is found at the _____, and each molecule binds about 50 Ca.

A

terminal cisterna

45
Q

Patients with MH have a _____ when they are given volatile anesthetics (such as halothane) for surgery.

A

catastrophic rise in body temperature

46
Q

The end of the SR at its contact with the _____ is called the terminal cisterna.

A

t-tubule

46
Q

Patients with MH have a catastrophic rise in body temperature when they are given _____ for surgery.

A

volatile anesthetics (such as halothane)

48
Q

Nebulin is associated with ______ and is thought to be important for keeping the thin filaments organized.

A

actin thin filaments

50
Q

_____ is associated with actin thin filaments and is thought to be important for keeping the thin filaments organized.

A

Nebulin

51
Q

Where is the DHP receptor located?

A

in all muscles

52
Q

_____ is found at the terminal cisterna, and each molecule binds about 50 Ca.

A

Calsequestrin

53
Q

The end of the SR at its contact with the t-tubule is called the _____.

A

terminal cisterna

55
Q

Bound to the _____ filaments are two important regulatory proteins, tropomyosin and troponin.

A

actin

55
Q

Calsequestrin is found at the terminal cisterna, and each molecule binds about _____.

A

50 Ca

55
Q

The DHP receptor is the cause of ______.

A

muscular dysgenesis

57
Q

In smooth muscle, removal of ____ is accomplished by pumps and Na-Ca exchangers in the sarcolemma.

A

Ca

59
Q

There are no _____ in cardiac muscle, so scar tissue forms.

A

satellite cells (stem cells)

60
Q

A _____ is a bundle of muscle cells.

A

fascicle

62
Q

The myosin in ____ cycles about 5 times per second.

A

slow twitch muscle

65
Q

An action potential in the motor axon causes release of the neurotransmitter _______.

A

acetylcholine (ACh)

66
Q

An ______ in the motor axon causes release of the neurotransmitter acetylcholine (ACh).

A

action potential

68
Q

Muscle cells contain several long contractile units called _____ that are composed of sarcomeres linked end to end.

A

myofibrils

69
Q

What is the current treatment for MH?

A

dantrolene

71
Q

Each skeletal muscle cell of a mammal is innervated at _____, usually near _____.

A

one spot; the center of the cell

72
Q

What is halothane?

A

a volatile anesthetic

73
Q

In MH, the _____ from the SR activates the Ca+2 ATPase to pump Ca+2 back into the SR and a futile, heat-producing cycle occurs and is lethal if not corrected.

A

steady Ca+2 leak

74
Q

How can skeletal muscle tension be graded?

A

1) increase freq of APs 2) recruit additional motor units 3) change the muscle length

76
Q

F-actin makes up the ______.

A

thin filaments

77
Q

An ______ in the SR causes a disease called malignant hyperthermia (MH).

A

abnormal calcium release channel

79
Q

______ result from the stacking of sarcomeres in precise register across the width of the myofiber.

A

Striations

81
Q

At the____, alpha-actinin is a molecule that crosslinks ______.

A

Z line; actin filaments

82
Q

Muscles that perform fine movements tend to have _____ while large muscles that make gross movements have ______.

A

small motor units; large motor units

84
Q

The myosin in _____ cycles about 20 times per second.

A

fast twitch muscle

84
Q

The ______ are used for postural or relatively maintained contractions.

A

slow oxidative fibers

85
Q

The thick filaments are 1.6 micrometers long and contain ______ myosins.

A

300-400

86
Q

The myofilaments are bundled into _____.

A

myofibrils

88
Q

Each troponin is bound to the end of one _____ molecules and induces a conformational change in the ______ that exposes the binding sites.

A

tropomyosin; tropomyosin

90
Q

The myosin in slow twitch muscle cycles about ___ times per second.

A

5

91
Q

In some cases FHC is due to mutations in ______.

A

troponin

92
Q

The rate of myosin turnover is _____ in fast twitch muscle than in slow twitch muscle.

A

faster

93
Q

The majority of people with FHC have mutations in the ______.

A

cardiac myosin heavy chain

95
Q

The RyR (ryanodine receptor) is in the SR membrane and is a ______.

A

Ca release channel

96
Q

The fast twitch fibers have high _____ content.

A

glycolytic

97
Q

In ______, [Ca]i is low (

A

normal, relaxed muscle

97
Q

Each myofibril is wrapped in its own ____.

A

SR

98
Q

____ links the myosin thick filaments to the Z-line.

A

Titin

100
Q

______ blocks muscle contraction by blocking Ca+2 release from the SR.

A

Dantrolene

101
Q

Actin exists as either _____ (______) or ______ (___).

A

G-actin (globular-single units); F-actin (filamentous)

101
Q

The rate of ______ is faster in fast twitch muscle than in slow twitch muscle.

A

myosin turnover

102
Q

One of the subunits of the DHP receptor is a voltage-gated Ca channel; the other molecule is the ______.

A

RyR (ryanodine receptor)

103
Q

_____ prevent the premature differentiation of satellite cells.

A

Fibroblasts

104
Q

Smooth muscle contains no _____, but calcium is still the key regulatory molecule.

A

troponin

105
Q

Depolarization of a muscle cell will open _____ and an action potential is initiated.

A

Na channels

107
Q

The _____ is the cause of muscular dysgenesis.

A

DHP receptor

108
Q

_____ is rod shaped and binds to 6-7 actin molecules of one strand.

A

Tropomyosin

109
Q

As strength increases, the _____ of each cell is increased; new myofibrils are formed.

A

cross sectional area

110
Q

The AChR is an ion channel that opens and causes ______.

A

depolarization

111
Q

Titin links the _____ to the _____.

A

myosin thick filaments; Z-line

112
Q

What is the mortality rate for MH?

A

10%

113
Q

Binding of ATP allows _____ to dissociate from _____.

A

myosin; actin

114
Q

Muscle cells contain several long contractile units called myofibrils that are composed of _____ linked end to end.

A

sarcomeres

115
Q

What is the contractile unit of the muscle called?

A

myofibril

116
Q

About _____ of all cases of sudden death due to cardiac arrest in young athletes are due to familial hypertrophic cardiomyopathy (FHC).

A

half

117
Q

Increased calcium in the smooth muscle cell binds to _____ and this binds to CaM kinase and activates it so that one of the _____ on the myosin head is phosphorylated.

A

calmodulin; light chains

119
Q

The _____ surrounds the entire muscle.

A

epimysium

120
Q

Virtually all muscles are a mix of _____ but each motor unit is ______.

A

all three types of fibers; homogeneous

121
Q

The _____ are bundled into myofibrils.

A

myofilaments

122
Q

As soon as myosin binds, it exerts a force of about ____.

A

5 pN

M2M Unit IV (11 decks)

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