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Pre-Pharm > A&P 9: Muscles & Muscle Tissue > Flashcards

A&P 9: Muscles & Muscle Tissue Flashcards

1
Q

Muscle fibers

A

skeletal and smooth muscle cells are elongated and thus called ___ ___

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2
Q

Myo- or mys-

A

muscle

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3
Q

Sarco-

A

flesh

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4
Q

Skeletal muscle tissue

A

packaged into the skeletal muscles, organs that attach to and cover the bony skeleton; striated

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5
Q

Voluntary muscle

A

skeletal muscle; acts under conscious control

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6
Q

Cardiac muscle tissue

A

occurs only in the heart, where it constitutes the bulk of the heart walls; striated, involuntary

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7
Q

Smooth muscle tissue

A

Found in the walls of hollow visceral organs, such as the stomach, urinary bladder, and respiratory passages; elongated cells with no striations; involuntary

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8
Q

Excitability

A

responsiveness; ability to receive and respond to a stimulus (any change in the environment inside or outside the body)

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9
Q

Contractility

A

ability to shorten forcibly when adequately stimulated; sets muscles apart from all other tissue types

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10
Q

Extensibility

A

ability to extend or stretch

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11
Q

Elasticity

A

ability of a muscle cell to recoil and resume its resting length after stretching

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12
Q

Skeletal muscle

A

each one is a discrete organ, made up of several kinds of tissues; skeletal muscle fibers predominate, but blood vessels, nerve fibers, and substantial amounts of connective tissue are also present

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13
Q

Epimysium

A

“outside the muscle”; overcoat of dense irregular connective tissue that surrounds the whole muscle; sometimes blends with the deep fascia that lies between neighboring muscles or the superficial fascia deep to the skin

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14
Q

Fascicles

A

within each skeletal muscle, the muscle fibers are grouped into these bundles

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15
Q

Perimysium

A

surrounding each fascicle is this layer of fibrous connective tissue

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16
Q

Endomysium

A

“within the muscle”; wispy sheath of connective tissue that surrounds each individual muscle fiber; consists of fine areolar connective tissue

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17
Q

Insertion

A

when a muscle contracts, the movable bone (_____) moves toward the immovable or less movable bone

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18
Q

Origin

A

when a muscle contracts, the movable bone (insertion) moves toward the immovable or less movable bone (___); typically lies proximal to the insertion

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19
Q

Direct (fleshy) attachments

A

the epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage

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20
Q

Indirect attachments

A

the muscle’s connective tissue wrappings extend beyond the muscle either as a ropelike tendon or as a sheetlike aponeurosis

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21
Q

Tendon

A

cord of dense fibrous tissue attaching muscle to bone

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22
Q

Aponeurosis

A

fibrous or membranous sheet connecting a muscle and the part it moves

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23
Q

Sarcolemma

A

plasma membrane of a skeletal muscle fiber/cell

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24
Q

Sarcoplasm

A

cytoplasm of a muscle cell; contains unusually large amounts of glycosomes

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25
Q

Glycosomes

A

granules of stored glycogen that provide glucose during muscle cell activity

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26
Q

Myoglobin

A

a red pigment that stores oxygen

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27
Q

Myofibrils

A

a single muscle fiber contains hundreds to thousands of these rodlike ____ that run parallel to its length; densely packed; account for about 80% of cellular volume

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28
Q

Striations

A

repeating series of dark and light bands; evident along the length of each myofibril

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29
Q

A bands

A

dark bands of a muscle fiber; aligned with I bands, give the cell its striated appearance

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30
Q

I bands

A

light bands of a muscle fiber; aligned with A bands, give the cell its striated appearance

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31
Q

H zone

A

each dark A band has this lighter region in its midsection

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32
Q

M line

A

each H zone is bisected vertically by this dark line, formed by molecules of the protein myomesin

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33
Q

Z disc (Z line)

A

each light I band has a midline interruption, a darker area called this

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34
Q

Sarcomere

A

the region of a myofibril between 2 successive Z discs; “muscle segment”; smallest contractile unit of a muscle fiber; the functional unit of skeletal muscle

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35
Q

Myofilaments (filaments)

A

smaller structures within sarcomeres; muscle equivalents of the actin- or myosin-containing microfilaments

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36
Q

Thick filaments

A

central filaments containing myosin (red); extend the entire length of the A band; connected in the middle of the sarcomere at the M line

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37
Q

Thin filaments

A

lateral filaments containing actin (blue); extend across the I band and partway into the A band

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38
Q

Myosin

A

protein that primarily composes thick filaments; each molecule consists of 2 heavy and 4 light polypeptide chains & has a rodlike tail attached by a flexible hinge to 2 globular heads; tail = 2 intertwined helical polypeptide heavy chains

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39
Q

Cross bridges

A

during contraction, the globular heads of myosin link the thick and thin filaments together, forming these, and swivel around their point of attachment

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40
Q

Actin

A

protein that chiefly composes the thin filaments; has kidney-shaped polypeptide subunits, called globular ___ or g ____, which bear the active sites to which the myosin heads attach during contraction

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41
Q

Tropomyosin

A

regulatory protein composed of polypeptide strands of these rod-shaped proteins that spiral around the actin core and help stiffen and stabilize it; arranged end to end along the actin filaments; in a relaxed muscle fiber, block myosin-binding sites on actin so that myosin heads on the thick filaments cannot bind to thin filaments

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42
Q

Troponin

A

major regulatory protein in thin filaments; globular 3-polypeptide complex; TnI = inhibitory subunit that binds to actin; TnT = binds to tropomyosin and helps position it on actin; TnC = binds calcium ions

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43
Q

Elastic filament

A

fiber formed from the protein elastin, which gives a rubbery and resilient quality to the matrix of connective tissue

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44
Q

Titin

A

giant protein that makes up elastic filaments; extends from the Z disc to the thick filament, then runs within the thick filament (forming its core) to attach to the M line; holds the thick filaments in place, thus maintaining the organization of the A band; helps the muscle spring back into shape after stretching

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45
Q

Dystrophin

A

important structural protein; links the thin filaments to the integral proteins of the sarcolemma, which in turn are anchored to the extracellular matrix

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46
Q

Sarcoplasmic reticulum (SR)

A

elaborate smooth endoplasmic reticulum; its interconnecting tubules surround each myofibril like a sleeve

47
Q

Terminal cisterns

A

“end sacs” that form large, perpendicular cross channels at the A band-I band junctions; always occur in pairs

48
Q

T tubule

A

“transverse” tubule; at each A band-I band junction, the sarcolemma of the muscle cell protrudes deep into the cell interior, forming this elongated tube; tremendously increases the muscle fiber’s surface area

49
Q

Triads

A

successive groupings of the 3 membranous structures (terminal cistern, T tubule, and terminal cistern)

50
Q

Contraction

A

activation of myosin’s cross bridges (force-generating sites)

51
Q

Sliding Filament Model of Contraction

A

during contraction, the thin filaments slide past the thick ones so that actin and myosin filaments overlap to a greater degree

52
Q

Action potential

A

a large transient depolarization event, including polarity reversal, that is conducted along the membrane of a muscle cell or nerve fiber; an electrical current

53
Q

Neuromuscular junction (end plate)

A

region where a motor neuron comes into close contact with a skeletal muscle cell; includes the axon terminals, the synaptic cleft, and the junctional folds of the sarcolemma

54
Q

Synaptic cleft

A

space separating an axon terminal and a muscle fiber; filled with gel-like extracellular substance rich in glycoproteins and collagen fibers

55
Q

Synaptic vesicles

A

small membranous sacs within the moundlike axon terminal; contain the neurotransmitter acetylcholine

56
Q

Acetylcholine (ACh)

A

chemical transmitter substance released by some nerve endings; a neurotransmitter

57
Q

Junctional folds

A

the trough-like part of the muscle fiber’s sarcolemma that helps form the neuromuscular junction is highly folded; these folds form a large surface area for the millions of ACh receptors located there

58
Q

ACh receptors

A

receptors located within the junctional folds of a neuromuscular junction

59
Q

Acetylcholinesterase

A

enzyme located in the synaptic cleft that quickly terminates the effects of ACh binding to the ACh receptors; breaks down ACh to its building blocks (acetic acid and choline); the removal of ACh prevents continued and most likely undesirable muscle fiber contraction in the absence of additional nervous system stimulation

60
Q

End Plate Potential

A

local depolarization of the neuromuscular junction - a transient change in membrane potential occurs as the interior of the sarcolemma becomes less negative

61
Q

Refractory Period

A

during repolarization, a muscle fibers is said to be in this, because the cell cannot be stimulated again until repolarization is complete

62
Q

Excitation-contraction (E-C) coupling

A

sequence of events by which transmission of an action potential along the sarcolemma causes myofilaments to slide

63
Q

Muscle tension

A

force exerted by contracting muscle on an object

64
Q

Load

A

opposing force exerted on the muscle by the weight of the object to be moved

65
Q

Motor unit

A

consists of 1 motor neuron and all the muscle fibers it innervates (supplies)

66
Q

Myogram

A

recording of contractile activity

67
Q

Muscle twitch

A

motor unit’s response to a single action potential of its motor neuron

68
Q

Latent period

A

first few milliseconds following stimulation when excitation-contraction coupling is occurring

69
Q

Graded muscle responses

A

variations in the strength of muscles as different demands are placed on them, which are needed for proper control of skeletal movement

70
Q

Wave (temporal) summation

A

if 2 identical stimuli (electrical shocks or nerve impulses) are delivered to a muscle in rapid succession, the 2nd twitch will be stronger than the 1st; on a myogram, the 2nd twitch will appear to ride on the shoulders of the 1st; occurs because the 2nd contraction occurs before the muscle has completely relaxed; contractions are added together

71
Q

Unfused (incomplete) tetanus

A

sustained but quivering contraction that happens if the stimulus strength is held constant and the muscle is stimulated at an increasingly faster rate; relaxation time between twitches becomes shorter and shorter; the concentration of Ca 2+ in the cytosol rises higher and higher; the degree of wave summation becomes greater and greater

72
Q

Fused (complete) tetanus

A

when all evidence of muscle relaxation disappears and contractions fuse into a smooth, sustained contraction plateau; happens infrequently

73
Q

Recruitment

A

multiple motor unit summation; controls the force of contraction more precisely

74
Q

Subthreshold stimuli

A

stimuli that produce no observable contractions

75
Q

Threshold stimulus

A

the stimulus at which the 1st observable contraction occurs

76
Q

Maximal stimulus

A

strongest stimulus that increases contractile force; represents the point at which all the muscle’s motor units are recruited

77
Q

Isotonic contractions

A

“same tension”; muscle length changes and moves a load

78
Q

Concentric contractions

A

isotonic contractions in which the muscle shortens and does work

79
Q

Eccentric contractions

A

isotonic contractions in which the muscle generates force as it lengthens

80
Q

Isometric contractions

A

tension may build to the muscle’s peak tension-producing capacity, but the muscle neither shortens nor lengthens; occur when a muscle attempts to move a load that is greater than the force (tension) the muscle is able to develop

81
Q

Muscle tone

A

state in which even relaxed muscles are almost always slightly contracted

82
Q

Creatine phosphate (CP)

A

unique, high-energy molecule stored in muscles; tapped to regenerate ATP while the metabolic pathways adjust to the suddenly higher demand for ATP

83
Q

Creatine kinase

A

enzyme that catalyzes the CP-ADP reaction; so efficient that the amount of ATP in muscle cells changes very little during the initial period of contraction

84
Q

Glycolysis

A

initial phase of glucose breakdown; “sugar splitting”

85
Q

Lactic acid

A

under anaerobic conditions, most of the pyruvic acid produced during glycolysis is converted into this

86
Q

Anerobic glycolysis

A

overall process of sugar-splitting that does not use oxygen; converts pyruvic acid into lactic acid

87
Q

Aerobic respiration

A

occurs in the mitochondria, requires oxygen, and involves a sequence of chemical reactions that break the bonds of fuel molecules and release energy to make ATP

88
Q

Aerobic endurance

A

the length of time a muscle can continue to contract using aerobic pathways

89
Q

Anaerobic threshold

A

point at which muscle metabolism converts to anaerobic glycolysis

90
Q

Muscle fatigue

A

state of physiological inability to contract even though the muscle still may be receiving stimuli

91
Q

Excess Postexercise oxygen consumption (EPOC)

A

formerly “oxygen debt”; extra amount of oxygen that the body must take in for restorative processes; represents the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used

92
Q

Internal tension

A

as a muscle begins to contract, the force generated by the cross bridges that stretches the connective tissue sheaths (noncontractile components)

93
Q

External tension

A

connective tissue sheaths become taut and transfer tension to the load (muscle insertion)

94
Q

Length-tension relationship

A

occurs when a muscle is slightly stretched and the thin and thick filaments overlap optimally; permits sliding along nearly the entire length of the thin filaments

95
Q

Slow fibers & fast fibers

A

variances in the velocity of fiber shortening; reflects how fast their myosin ATPases split ATP

96
Q

Oxidative fibers

A

the cells that rely mostly on the oxygen-using aerobic pathways for ATP generation

97
Q

Glycolytic fibers

A

cells that rely on anaerobic glycolysis for ATP generation

98
Q

Classifications of skeletal muscle cells (3)

A

slow oxidative fibers, fast oxidative fibers, or fast glycolytic fibers

99
Q

Aerobic (endurance) exercise

A

swimming, jogging, fast walking, biking; result in several recognizable changes in skeletal muscles (1) number of capillaries surrounding the muscle fibers increases (2) the number of mitochondria within the muscle fibers increases (3) the fibers synthesize more myoglobin

100
Q

Resistance exercise

A

muscle hypertrophy results mainly from this high-intensity exercise, typically under anaerobic conditions; ex. weight-lifting, isometric exercises (pits muscles against high-resistance or immovable forces)

101
Q

Overuse injuries

A

doing too much too soon, or ignoring warning signs of muscle or joint pain may lead to lifetime disability

102
Q

Peristalsis

A

alternating contraction and relaxation that squeezes substances through an organ’s internal pathway; propulsive action

103
Q

Varicosities

A

numerous bulbous swellings that release neurotransmitter into a wide synaptic cleft in the general area of the smooth muscle cells

104
Q

Diffuse junctions

A

junctions in which varicosities release neurotransmitter in the general area of smooth muscle cells

105
Q

Caveolae

A

pouchlike infoldings that sequester bits of extracellular fluid containing a high concentration of Ca2+ close to the membrane

106
Q

Dense bodies

A

cytoplasmic structures tethered to the sarcolemma; act as anchoring points for thin filaments and therefore correspond to Z discs of skeletal muscle

107
Q

Calmodulin

A

regulatory molecule; cytoplasmic calcium-binding protein; interacts with myosin kinase or myosin light chain kinase

108
Q

Myosin kinase/myosin light-chain kinase

A

phosphorylates myosin (and activates it)

109
Q

Stress-relaxation response

A

allows a hollow organ to fill or expand slowly to accommodate a greater volume without causing strong contractions that would expel its contents (stomach, intestine, bladder)

110
Q

Unitary smooth muscle

A

AKA visceral muscle; in the walls of all hollow organs except the heart; very common

111
Q

Multi unit smooth muscle

A

the smooth muscles in the large airways to the lungs and in large arteries, the arrector pili muscles attached to hair follicles, and the internal eye muscles that adjust pupil size and allow the eye to focus visually

112
Q

Myoblasts

A

all 3 types of muscle tissue develop from embryonic mesoderm cells called _____

113
Q

Muscular dystrophy

A

group of inherited muscle-destroying diseases that generally appear during childhood

114
Q

Duchenne Muscular Dystrophy

A

most common and serious form of muscular dystrophy; inherited as a sex-linked recessive disease; expressed almost exclusively in males; caused by a defective gene for dystrophin, a cytoplasmic protein that links the cytoskeleton to the extracellular matrix & helps stabilize the sarcolemma

Pre-Pharm (182 decks)

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