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Chapter 11 Flashcards

1
Q

Characteristics of all muscle cells?

A

Conductivity, contractibility, excitability, extensibility, elasticity

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2
Q

What is excitability?

A

Responding to stimulation w/ electrical charges

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3
Q

What is conductivity?

A

When a small local excitation sets off a wave that leads to contraction

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4
Q

What is contractibility?

A

Shortening when stimulated

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5
Q

What is extensibility?

A

Stretching between contractions

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6
Q

What is elasticity?

A

Returning to original rest length after being stretched

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7
Q

What is skeletal muscle?

A

The muscles that move our body. Voluntary, striated

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8
Q

What are striations?

A

Light and dark transverse bands on muscle, representing overlapping arrangements of contractile proteins

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9
Q

What does voluntary mean?

A

Muscles that are subject to conscious control (skeletal)

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10
Q

What does involuntary mean?

A

Muscles that are not under conscious control. Never attached to bones (cardiac and smooth)

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11
Q

What are skeletal muscle cells called?

A

Muscle fibers or myofibers

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12
Q

What is skeletal muscle composed of?

A

The muscular tissue as well as fibrous connective tissue (endomysium, perimysium, epimysium)

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13
Q

How do bones move?

A

A muscle contracts, pulling on the collagen fibers continuous with tendons and a bone matrix, moving the bone

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14
Q

What properties does collagen have?

A

It is somewhat extensible and elastic

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15
Q

How does collagen assist with muscle stretching?

A

It helps prevent excessive stretching

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16
Q

What happens with collagen when a muscle relaxes?

A

The elastic recoil helps the muscle return to its resting length

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17
Q

Does collagen’s recoil help muscles with power?

A

It’s unclear

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18
Q

What are tendons?

A

Attachments between muscle and bone
matrix

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19
Q

What is the plasma membrane of a muscle fiber?

A

Sarcolemma

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20
Q

What is the cytoplasm of a muscle fiber?

A

Sarcoplasm

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21
Q

What are the protein cords occupying most of the sarcoplasm?

A

Myofibrils

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22
Q

What is glycogen?

A

Found in sarcoplasm, a carb that provides energy for the cell during exercise

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23
Q

What is myoglobin?

A

A red, oxygen-binding pigment which provides oxygen during exercise

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24
Q

How many nuclei are in a muscle cell? Where are they?

A

Multiple, they’re pressed against the inside of the sarcolemma

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25
Q

What are myoblasts?

A

Specialized stem cells which fuse to produce muscle fibers

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26
Q

What are satellite cells?

A

Unspecialized stem cells between the muscle fiber and endomysium. They help regenerate damaged skeletal muscle

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27
Q

Where are the mitochondria of a muscle cell?

A

Packed into spaces between myofibrils

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28
Q

What is the smooth endoplasmic reticulum of a muscle cell?

A

Sarcoplasmic reticulum

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29
Q

What does sarcoplasmic reticulum do?

A

Form a network around each myofibril, and exhibit terminal cisterns

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30
Q

What are terminal cisterns?

A

Dilated end-sacs of SR which cross the muscle fiber from one side to the other

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31
Q

What do terminal cisterns do regarding calcium?

A

It acts as a reservoir. It releases calcium through channels to activate contraction

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32
Q

What are transverse tubules (T tubules)?

A

Tubular infoldings in the sarcolemma, which penetrate through the cell and emerge on the other side

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33
Q

What is a triad?

A

A T tubule and the 2 terminal cisterns associated with it

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34
Q

What is required for a muscle to contract?

A

Calcium ions (Ca+)

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35
Q

Where does a muscle cell store its calcium when at rest?

A

The sarcoplasmic reticulum, bound to calsequestrin

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36
Q

What happens to calcium when a cell is stimulated?

A

T tubules signal to ion gates in the SR membrane to open, flooding Ca+ into the cytosol

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37
Q

What are myofilaments?

A

Long proteins that fill most of the muscle cell. They make up myofibrils

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38
Q

What are thick filaments?

A

A type of myofilament. Made of several hundred molecules of a protein called myosin

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39
Q

How are thick filaments shaped?

A

2 chains of myosin make a tail and a double globular head that projects out from an angle. Each myosin is shaped like a golf club

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40
Q

What are thin filaments?

A

A type of myofilament. Composed of 2 intertwined strands of a protein called fibrous actin (F actin), and molecules of tropomyosin

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41
Q

How is F actin made?

A

By a string of subunits called globular actin (G actin)

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42
Q

How does G actin work?

A

It has active sites that can bind to the heads of myosin molecules

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43
Q

What is tropomyosin?

A

Found in thin filaments, it is released when a muscle fiber is relaxed, and blocks the active sites of actins so myosin cannot bind to them

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44
Q

What is bound to tropomyosin?

A

It has calcium-binding proteins called troponin bound to it

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45
Q

What are elastic filaments?

A

A type of myofilament, made of a huge spongy protein called titin

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46
Q

Where are elastic filaments?

A

Through the core of each thick filament, anchoring it to the Z disc at one and and M line at the other

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47
Q

What does titin do?

A

Stabilize the thick filament, centering it between thin filaments, preventing overstretching, and recoiling it like a spring after a muscle is stretched

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48
Q

What are contractile proteins?

A

Myosin and actin. Shorten the muscle fiber

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49
Q

What are regulatory proteins?

A

Tropomyosin and troponin. Act like a switch to determine when a muscle fiber can and cannot contract

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50
Q

What is dystrophin?

A

An accessory protein which is located between the sarcolemma and outermost myofilaments

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51
Q

What does dystrophin do?

A

Links actin in outermost myofilaments to endomysium

52
Q

What happens to dystrophin when thin filaments move?

A

It gets pulled on, in turn pulling the extracellular connective tissues that lead to a tendon

53
Q

How is muscular dystrophy caused?

A

Genetic defects in dystrophin

53
Q

How is contraction activated?

A

Calcium is released into the sarcoplasm. It binds to troponin. Troponin changes shape and moves tropomyosin off of the actin’s active sites

54
Q

What are striations?

A

Bands made from the organization of myosin and actin (contractile proteins) in cardial and skeletal muscle cells

55
Q

What are A bands?

A

Dark bands of striated muscle. Thick and thin filaments overlap. Anisotrophic

56
Q

What are I bands?

A

Light bands of striated muscle. Only thin filaments and elastic fibers. Isotrophic

57
Q

What is the H band?

A

In the middle of an A band, a lighter region where it’s only thick filaments

58
Q

What is the M line?

A

The middle of an H band

59
Q

What is a Z disc?

A

An anchor for thin filaments and elastic fibers. Bisects the I bands

60
Q

What is a sarcomere?

A

A segment of a myofibril from one Z disc to another. The functional contractile units of the muscle fiber

61
Q

How do muscle cells shorten?

A

The individual sarcomeres shorten, pulling Z discs to one another. The dystrophin and linking proteins pull on the extracellular proteins of the muscle. They pull on the sarcolemma to achieve cell shortening

62
Q

Do thick or thin filaments change length during shortening?

A

No, they just overlap more

63
Q

What is denervation atrophy?

A

When a muscle degrades from being paralyzed for so long

64
Q

What are skeletal muscle cells innervated by?

A

Somatic nerve cells

65
Q

Where are the cell bodies of somatic nerve cells?

A

Brainstem and spinal cord

66
Q

What is a motor unit?

A

One nerve cell and all of the muscle fibers innervated by it

67
Q

What are small motor units for?

A

Fine control

68
Q

What are large motor units for?

A

Strength

69
Q

What is a synapse?

A

The point where a nerve fiber meets its target

70
Q

What is a neuromuscular junction?

A

A synapse where the target cell is a muscle fiber

71
Q

What is an axon terminal?

A

The point where a nerve fiber ends

72
Q

What are synaptic vesicles?

A

Organelles in axon terminals where acetylcholine is found

73
Q

What is acetylcholine?

A

AKA ACh, a neurotransmitter that acts as a chemical messenger from nerve cell to plasma cell

74
Q

What is a synaptic cleft?

A

The gap between an axon terminal and sarcolemma

75
Q

What are junctional folds?

A

Infolds in the sarcolemma that increase ACh-sensitive membrane’s surface area

76
Q

What are ACh receptors?

A

Proteins embedded in the sarcolemma

77
Q

What is a basal lamina?

A

Covering the NMJ, it separates the muscle fiber and nerve ending from surrounding connective tissue

78
Q

What is acetylcholinesterase?

A

AKA AChE, an enzyme that breaks down ACh after it’s stimulated a muscle, so it can relax

79
Q

Are muscle and nerve cells electrically excitable?

A

Yes

80
Q

What is electrophysiology?

A

The study of the electrical activity of cells

81
Q

What is voltage?

A

Difference in electrical charge from one point to another

82
Q

What is polarized?

A

The intracellular fluid, it has more anions than the ECF

83
Q

What is resting membrane potential usually at?

A

-90 mv in skeletal muscle cells

84
Q

What happens to ion concentration when a nerve or muscle cell is stimulated?

A

Na+ ions flood into the cell, overriding the negative charge inside the membrane and turning it positive. AKA, depolarization

85
Q

What happens to the ion concentration after depolarization?

A

K+ exits the cell, repolarizing the membrane. The loss of positive potassium ions turned the membrane negative again

86
Q

What is action potential?

A

The quick shift in electrical charge within a membrane

87
Q

How does action potential spread?

A

It acts as a wave, producing a nerve impulse

88
Q

How can toxins cause paralysis?

A

They can bind to AChE and prevent it from degrading ACh, leading to spastic paralysis, or, they can compete w/ ACh for receptor sites, leading to flaccid paralysis

89
Q

What is excitation?

A

Process in which nerve action potentials lead to muscle action potentials

90
Q

What is excitation-contraction coupling?

A

Events that link the action potentials on the
sarcolemma to activation of the myofilaments, thereby preparing them to contract

91
Q

What is contraction?

A

Step in which the muscle fiber develops tension and may shorten

92
Q

What is sliding filament theory?

A

The mechanism of contraction. Thin filament slides over thick filament, pulling Z discs, shortening sarcomere, generating tension

93
Q

What is the length-tension relationship?

A

The amount of tension generated by a muscle depends on how stretched or shortened it was before stimulation

94
Q

What is optimum resting length?

A

2.0-2.25 µm

95
Q

How does rigor mortis work?

A

Calcium is released into cytosol and it starts the myosin-actin crossbridging, but theres no ATP for the muscle to relax with

96
Q

What happens during excitation?

A

A nerve signal opens the calcium channels, letting them enter the synaptic terminal. This tells the vesicles to release ACh, which binds to sarcolemma and opens the channel so Na+ can come in and K+ can go out, making an end-plate potential. Then, more channels for Na+ and K+ open in response, causing an action potential

97
Q

What happens during excitation-contraction coupling?

A

A wave of action potentials hits the T tubules, bringing them down into the cell, opening ion channels in the T tubules. This in turn opens channels in the SR so calcium can enter the cytosol. Calcium binds to the troponin on thin filaments, changing the chape of the troponin-tropomyosin complex, so the active sites on actin are exposed and ready for myosin

98
Q

What happens during contraction?

A

The myosin head needs ATP on it. Then, the ATP turns into ADP and phosphate, which also activates the head. The head binds to an active site on actin, making a crossbridge. It lets go of the ADP and P and bends down, pulling the thin filament with it (power stroke). Then a new ATP binds to myosin, breaking the bridge (recovery stroke), and the myosin attaches to a new active site farther down

99
Q

What can contraction be compared to?

A

Pulling an anchor up by a rope

100
Q

What happens during relaxation?

A

Nerve signals stop arriving at the NMJ, so ACh stops getting released. AChE breaks it down and it gets reabsorbed into the SR. The calcium levels fall dramatically and tropomyosin moves back to blocking active sites on the actin

101
Q

What are myocytes?

A

Any type of muscle cell

102
Q

What are cardiomyocytes?

A

Cardiac muscle cells

103
Q

What’s the difference between cardiac and smooth muscle, and skeletal muscle?

A

Skeletal is voluntary, the others are not

104
Q

Purpose of cardiac muscle?

A

Pump blood

105
Q

What are intercalated discs?

A

Intercellular connections on cardiomyocytes. Allow electrical impulse conduction from cell to cell

106
Q

What nervous system is associated w/ cardiac muscle?

A

Autonomic nervous system

107
Q

What nervous system is associated w/ skeletal muscle?

A

Somatic nervous system

108
Q

What nervous system is associated with smooth muscle?

A

Autonomic nervous system

109
Q

How do cells in cardiac muscle contract?

A

In unison

110
Q

How long do contractions of cardiac muscle need to last?

A

Long enough to expel blood

111
Q

How do damaged cardiac muscle cells regenerate?

A

Fibrosis (scar tissue)

112
Q

How does the autonomic nervous system affect cardiac muscle?

A

Increases or decreases heart rate/contraction strength

113
Q

How do smooth muscles get nerve supply?

A

Some get it from autonomic fibers

114
Q

How does smooth muscle regenerate?

A

Mitosis

115
Q

What is smooth muscle for?

A

It lines the internal walls of viscera and does some fine control

116
Q

What is unique to smooth muscle’s method of contraction?

A

It’s really slow but it can stay contracted for a while

117
Q

What are dense bodies?

A

Protein plaques in place of Z discs in smooth muscle

118
Q

What is a multiunit smooth muscle?

A

Autonomic innervation, branches synapse w/ myocytes to form a motor unit

119
Q

What is a single-unit smooth muscle?

A

AKA visceral muscle, electrically couples to each other via gap junctions. Stimulate each other, so they contract as a unit

120
Q

What excites smooth muscle?

A

Autonomic nervous system, chemicals, temperature, stretch, autorhythmicity

121
Q

What is contraction triggered by, energized by, and achieved by?

A

Triggered by calcium ions, energized by ATP, achieved by sliding filaments

122
Q

What is latch-bridge mechanism?

A

Heads of myosin molecules in smooth muscle don’t detach actin immediately and dont consume more ATP

123
Q

What is muscular dystrophy?

A

Hereditary diseases where skeletal muscles degenerate and are replaced w/ fat and fibrous scar tissue

124
Q

What is duchenne?

A

A form of muscular dystrophy, common in boys 2-10

125
Q

What is myasthenia gravis?

A

A form of muscular dystrophy, antibodies attach NMJs and bind ACh receptors together. Women 20-40

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