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A&P > Muscle Tissue > Flashcards

Muscle Tissue Flashcards

1
Q

How does muscle tissue contribute to homeostasis?

A

produce body movements, moving substances through the body, and produce heat to maintain body temp

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2
Q

What is authorhythmicity?

A

built in rhythm of the cardiac and some smooth muscle

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3
Q

No Mr. Rose

A

.

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4
Q

4 Special properties of muscle tissue

A

electrical excitability, contractility, extensibility, elasticity

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5
Q

What is electrical excitability?

A

ability to respond to certain stimuli by producing electrical signals called action potentials

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6
Q

Purpose and composition of hypodermis

A

protects muscle, composed of areolar and adipose tissue

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7
Q

Fascia

A

dense sheet of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other organs; holds muscles with similar function together

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8
Q

3 Layers of connective tissue that extend from fascia to protect and strengthen skeletal muscle

A

epimysium, perimysium, endomysium

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9
Q

Epimysium

A

outer layer, encircles entire muscle, consists of dense irregular connective tissue

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10
Q

Perimysium

A

dense irregular connective tissue, surrounds groups of 10 to 100 muscle fibers- separtes them into fascicles

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11
Q

Endomysium

A

penetrates the interior of each fascicle and separates individual muscle fibers from one another; mostly reticular fibers

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12
Q

Aponeurosis

A

connective tissue elements extend as a broad, flat sheet

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13
Q

What neuron stimulates skeletal muscle? What provides blood supply?

A

somatic motor neuron (axon branches and connects to muscle), capillaries

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14
Q

Sarcolemma

A

plasma membrane of a muscle cell

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15
Q

Transverse (T) tubules

A

invaginations of the sarcolemma, tunnel in from the surface toward the center of each muscle fiber, filled with interstitial fluid

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16
Q

What is the sarcoplasm and what does it contain?

A

cytoplasm of muscle fiber; much glycogen, myoglobin

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17
Q

What is myoglobin?

A

protein that binds O2 that diffuses into muscle from ISF, releases O2 when it is needed by mitochondria

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18
Q

Myofibrils

A

contractile organelles of skeletal muscle; stuffed inside sarcoplasm

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19
Q

Sarcoplasmic reticulum

A

fluid-filled system of membranous sacs that encircle each myofibril

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20
Q

Terminal cisterns

A

dilated end sacs of the sarcoplasmic reticulum; butt afaints the T tubule from both sides; releases calcium ions in muscle contractions

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21
Q

Triad

A

a T tubule and the 2 terminal cisterns on either side of it

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22
Q

2 Myofilaments of myofibrils

A

thin and thick filaments

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23
Q

Thin filaments

A

composed of the protein actin

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24
Q

Thick filaments

A

composed of the protein myosin

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25
Q

Sarcomere

A

basic functional unit of a myofibril, extend from one Z disc to the next

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26
Q

Z discs

A

narrow, plate-shaped region of dense protein that separate one sarcomere from the next

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27
Q

A band

A

darker middle part of the sarcomere, extends the entire length of the thick filaments

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28
Q

I band

A

lighter, less dense area that contains the rest of the thin filaments (no thick)

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29
Q

H zone

A

center of each A band, contains only thick filaments

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30
Q

M line

A

supporting proteins that hold the thick filaments together at the center of the H zone

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31
Q

What are the two contractile proteins in muscle fibers?

A

actin and myosin

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32
Q

Myosin

A

make up thick filaments, motor protein (pulls on structures to achieve movement); myosin tail points toward the M line and the 2 myosin heads have binding sites

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33
Q

What are the binding sites on myosin heads?

A

actin-binding site and ATP-binding site

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34
Q

How many thin filaments surround each thick filament?

A

6

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35
Q

Actin

A

make up thin filaments, each molecule has a myosin-binding site

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36
Q

Tropomyosin

A

regulatory protein in thin filaments, covers myosin binding site in relaxed muscle

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37
Q

Troponin

A

regulatory protein in thin filaments, moves tropomyosin out of the way

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38
Q

List the structural proteins of myofibrils

A

titin, α-actinin, myomesin, nebulin, dystrophin

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39
Q

What is the 3rd most plentiful protein in skeletal muscle?

A

titin

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40
Q

Titin

A

connects a Z disc to the M line, helps stabilize the position of the thick filament; very elastic- helps sarcomere return to its resting position

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41
Q

Level of organization of skeletal muscle

A

skeletal muscle -> fascicle -> muscle fiber -> myofibril -> filaments

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42
Q

Sliding filament mechanism

A

myosin heads pull the thin filaments toward the M line; the I band and H zone narrow and then disappear when muscle is maximally contracted

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43
Q

What initiates the contraction cycle?

A

release of calcium ions from the sarcoplasmic reticulum which binds to troponin which moves tropomyosin out of the way

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44
Q

4 Steps in the contraction cycle

A

(1) ATP hydrolysis (2) attachement of myosin and actin (3) power stroke (4) detachement of myosin and actin

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45
Q

What is excitation-contraction coupling?

A

sequence of events that links excitation (muscle action potential) to contraction (sliding of the filaments)

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46
Q

Process of excitation-contraction coupling

A

AP enters T tubules and opens voltage gated calcium channels, once voltage channels are open calcium release channels release calcium from SR into sarcoplasm, calcium binds to troponin which moves tropomyosin; calcium-ATPase pumps pump calcium back into SR

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47
Q

Calsequestrin

A

protein inside SR that bind calcium and allow even more calcium to be stored in the SR

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48
Q

T/F calcium is 10 000 times higher in the sarcoplasm of a relaxed muscle than in the SR

A

False. It’s 10 000 times higher in the SR than the sarcoplasm

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49
Q

What is the length-tension relationship in skeletal muscles?

A

the forcefulness of muscle contraction depends on the length of the sarcomeres within a muscle before contraction begins

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50
Q

What does the neuromuscular junction consist of?

A

synaptic end bulbs, synaptic cleft, motor end plate of the muscle fiber

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51
Q

What neuron stimulates skeletal muscle fibers?

A

somatic motor neurons

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52
Q

Synapse

A

a region where communication occurs between 2 neurons or between a neuron and target cell

53
Q

Synaptic cleft

A

gap in synapse that separates 2 cells

54
Q

What is the axon terminal?

A

end of the motor neuron at the NMJ

55
Q

Synaptic end bulbs

A

clusters of the end of the axon terminal

56
Q

Synaptic vesicles

A

membrane enclosed sacs suspended in the cytosol within each synaptic end bulb, contain acetylcholine

57
Q

Motor end plate

A

region of the sarcolemma opposite the synaptic end bulbs

58
Q

ACh receptors

A

integral transmembrane proteins on motor end plate, ligand-gated ion channels

59
Q

Junctional folds

A

deep groves in the motor end plate that provide a large surface area for ACh receptors

60
Q

4 Steps in muscle action potential

A

(1) release of ACh (2) activation of ACh receptors (3) production of muscle AP (4) termination of ACh activity

61
Q

3 Ways muscle fibers produce ATP

A

creatine phosphate, anaerobic glycolysis, aerobic respiration

62
Q

Which form of ATP production is unique to muscle fibers?

A

creatine phosphate

63
Q

What is creatine?

A

small, amino-acid like molecule that is synthesized in the liver, kidneys, and pancreas and then transported to muscle fibers

64
Q

T/F Creatine phosphate is the first source of energy when muscle contractions begin

A

True

65
Q

How does creatine phosphate work to produce ATP?

A

creatine phosphate is plentiful in the sarcoplasm; when muscle contractions begin, creatine kinase catalyzes the transfer of a phosphate group from creatine phosphate back to ADPx; occurs very rapidly

66
Q

How long do the stores of creatine phosphate and ATP provide energy for muscles to contract?

A

15 seconds

67
Q

Where does glycolysis occur and how much net ATP does it produce?

A

cytosol, 2 ATP

68
Q

What is are the products of anaerobic glycolysis?

A

2 lactic acid and 2 ATP

69
Q

How long does anearobic glycolysis provide energy for muscle contraction?

A

2 minutes

70
Q

What does that catabolism of glucose produce (glycolysis)?

A

2 pyruvic acid

71
Q

Aerobic respiration

A

When sufficient oxygen is present, the pyruvic acid formed by glycolysis enters the mitochondria where is undergoes aerobic respiration

72
Q

What to reaction cycles/chains make up aerobic respiration?

A

the Krebs cycle and electron transport chain

73
Q

How much ATP is produced from the catabolism of 1 glucose via aerobic respiration?

A

30-32 ATP

74
Q

What are the 2 sources of oxygen for muscle tissue?

A

oxygen that diffuses into muscle fibers from the blood and oxygen released by myoglobin within muscle fibers

75
Q

Muscle fatigue

A

the inability of a muscle to maintain force of contraction after prolonged activity

76
Q

Mechanisms that cause muscle fatigue

A

inadequate calcium in sarcoplasm, depletion of creatine phosphate, insufficient oxygen, depletion of glycogen and other nutrients, buildup of lactic acid and ADP, failure of AP’s to release enough ACh

77
Q

How does extra oxygen restore metabolic conditions to the resting level?

A

convert lactic acid back into glycogen stores in the liver, resynthesize creatine phosphate and ATP in muscle fibers, replace the oxygen removed from myoglobin

78
Q

Oxygen debt

A

added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise

79
Q

Recovery oxygen uptakes

A

better term than oxygen debt for the elevated use oxygen after exercise

80
Q

Motor unit

A

consists of a somatic motor neuron plus all of the skeletal muscle fibers it stimulates

81
Q

T/F All the muscle fibers in one motor unit contract in unison

A

True

82
Q

What does the total strength of a contraction depend on?

A

size of the motor units and the number that are activated at a given time

83
Q

Twitch contraction

A

brief contraction of all muscle fibers in a motor unit in response to a single AP in its motor neuron

84
Q

Latent period

A

time between stimulus application and muscle contraction; muscle AP sweeps over sarcolemma and calcium is released from SR; 2 msec

85
Q

Contraction period

A

calcium binds to troponin, myosin-binding sites on actin are exposed, and cross-bridges form; 10-100 msec

86
Q

Relaxation period

A

calcium actively transported back into SR, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle decreases; 10-100 msec

87
Q

Refractory period

A

period of lost excitability in which another contraction cannot occur

88
Q

Wave summation

A

stimuli arriving at different times causes larger contractions

89
Q

Unfused (incomplete) tetanus

A

sustained wavering contraction, occurs when a skeletal muscle is stimulated 20-30 timers per sec and the muscle can only partially relax

90
Q

Fused (complete) tetanus

A

sustained contraction in which individual twitches cannot be detected; occurs when a skeletal muscle is stimulated 80-100+ times per sec and the muscle does not relax

91
Q

When does wave summation and tetanus occur?

A

when additional calcium is released from the SR by subsequent stimuli while calcium is still high in the sarcoplasm from the first stimuli

92
Q

Motor unit recruitment

A

process in which the number of active motor units increases

93
Q

T/F motor unit recruitment contributes to smooth movements

A

true

94
Q

T/F large motor units = smoother movements

A

false. Smaller = smoother

95
Q

Muscle tone

A

small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units

96
Q

Define flaccid and when does it occur

A

a state of limpness in which muscle tone is lost; when the motor neurons serving a skeletal muscle are damaged or cut

97
Q

What do the motor units do to maintain muscle tone?

A

alternate being active and inactive in a shifting pattern

98
Q

Isotonic contraction

A

the tension (force of contraction) developed in the muscle remains almost constant while the muscle changes length

99
Q

What are isotonic contractions used for?

A

body movements and moving objects

100
Q

2 Types of isotonic contractions

A

concentric and eccentric

101
Q

Concentric isotonic reactions

A

tension generated is enough to overcome the resistance of the object being moved, the muscle shortens and produces movement eg. picking up a book from the table

102
Q

Eccentric isotonic contraction

A

tension exerted by the myosin cross-bridge resists movement of a load; the length of the muscle increases during a contraction eg. lowering the book back onto the table

103
Q

Isometric contraction

A

tension generated is not enough to exceed the resistance of the object being moved; the muscle does not change lengths eg. holding a book out in front of you

104
Q

What are isometric contractions used for?

A

stabilize joints while others are moved

105
Q

Red muscle fibers

A

skeletal muscle fibers that have a high myoglobin content, appear darker, contain more mitochondria, and are supplied by more blood capillaries

106
Q

White muscle fibers

A

skeletal muscle fibers that have a low content of myoglobin and appear lighter

107
Q

Slow oxidative (SO) fibers

A

contain large amounts of myoglobin and many blood capillaries, generate ATP mainly by aerobic respiration, ATPase hydrolyzes ATP slowly, contraction cycle is slow, very resistive to fatigue; for maintaining posture and aerobic endurance (marathon)

108
Q

Fast oxidative-glycolytic (FOG) fibers

A

largest fibers, contain large amounts of myoglbin and capillaries, generate lots of ATP via aerobic respiration, high intracellular glyocogen level so also generate ATP by anaerobic glycolysis, ATPase hydrolyzes ATP 3-5 times faster than SO; for walking or sprinting

109
Q

Fast glycolytic (FG) fibers

A

low myoglobin, few capillaries, few mitochondria; contain large amounts of glycogen and generate ATP mainly by glycolysis; contract strongly and quickly; for intense anaerobic movements for short duration eg. weight lifting, throwing ball

110
Q

T/F About 1/2 the fibers in skeletal muscle are FOG fibers

A

false. SO fibers

111
Q

T/F a motor unit contains a mixture of skeletal muscle fibers

A

false. All the same type of fiber

112
Q

Intercalated discs

A

irregular transverse thickenings of the sarcolemma that connect the ends of cardiac muscle fibers to one another

113
Q

What time of cell junctions are in the intercalated discs?

A

desmosomes (hold fibers together) and gap junctions

114
Q

Which muscle tissue layer does cardiac muscle lack?

A

epimysium

115
Q

T/F a cardiac muscle contraction lasts 10 to 15 times longer than a skeletal muscle contraction

A

true

116
Q

Visceral (single-unit) smooth muscle tissue

A

contract in unison as a single unit, autorhythmic, connected via gap junctions; found in the skin, walls of small arteries, hollow organs (stomach, intestines, uterus, bladder)

117
Q

Multi-unit smooth muscle tissue

A

consists of individual fibers, each with its own motor neuron terminals and with few gap junctions; stimulation of one fiber results in contraction of only that fiber; found in the walls of large arteries, airways, arrector pilli muscles, iris, and lens

118
Q

What are caveolae?

A

small pouchlike invaginations of the plasma membrane in smooth muscle that contain extracellular calcium to be used in contractions

119
Q

Dense bodies

A

thin filaments of smooth muscle attach to same, some dispersed throughout sarcoplasm, others are attache to sarcolemma; similar to Z discs

120
Q

T/F Smooth muscle lacks T tubules

A

true

121
Q

How does a smooth muscle contract?

A

thick and thin filaments generate tension thats transmitted to intermediate filaments, intermediate filaments pull on dense bodies attached to sarcolemma causing lengthwise shortening of the muscle fiber; as muscle contracts it rotates as a corkscrew turns

122
Q

Differences of smooth muscle

A

contracts slower but longer, can shorten and stretch to a greater extent, smaller reservoir of calcium

123
Q

Calmodulin

A

regulatory protein in smooth muscle that binds to calcium in the sarcoplasm; activates an enzyme called myosin light chain kinase which adds a phosphate group to the myosin head so it can contract

124
Q

Smooth muscle tone

A

state of continued partial contraction caused by the prolonged presence of calcium in the cytosol

125
Q

What initiates contraction/relaxation of smooth muscle?

A

autonomic nervous system, stretching, hormones, changes in pH, oxygen and carbon dioxide levels, temperature, ion concentrations

126
Q

Stress-relaxation response

A

phenomenon in smooth muscle when a smooth muscle fiber is stretched it initially contracts and then the tension decreases

127
Q

Hypertrophy

A

enlargement of existing cells

128
Q

Hyperplasia

A

increase in the number of fibers

129
Q

T/F Skeletal muscle fibers cannon undergo cellular division

A

true

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