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Human Physiology Block 1 > Muscle: Structure and Function > Flashcards

Muscle: Structure and Function Flashcards

1
Q

skeletal muscle generally attach to bones through what?

A

tough connective tissue tendons

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2
Q

a muscle attaches to the more fixed bone at its

A

origin

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3
Q

a muscle attaches to the more movable bone at its

A

insertion

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4
Q

decrease angle of joint

A

flexors

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5
Q

increase angle of joint

A

extensors

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6
Q

prime mover of any skeletal movement

A

agonist

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7
Q

muscles that act on the same joint to produce opposite actions

A

antagonists

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8
Q

fibrous connective tissue from tendons forms sheaths called ( ) that extend around and into skeletal muscle

A

epimysium

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9
Q

inside the muscle, the epimysium divides muscle into columns called ( )

A

fascicles

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10
Q

connective tissue around fascicles

A

perimysium

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11
Q

muscle fibers are ensheathed by a thin connective tissue layer called the ( )

A

endomysium

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12
Q

the plasma membrane of the muscle is called what?

A

sarcolemma

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13
Q

muscles are similar to other cells except they are ( )

A

multinucleate and striated

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14
Q

what does the NMJ include?

A

1) the single synaptic ending of the motor neuron that’s innervating each muscle fiber
2) underlying specializations of sarcolemma

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15
Q

the place on the sarcolemma where the NMJ occurs is the

A

motor end plate

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16
Q

Ach release can be inhibited by what?

A

Botulinum toxin (botox)

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17
Q

The Ach transduces the signal and it can be inhibited by what?

A

curare

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18
Q

what inhibits AchEsterase release?

A

neostigmae

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19
Q

each fiber contains bundles of subunits called ( ), which make up about 80% of the fiber volume

A

myofibrils

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20
Q

myofibrils are packed with ( ), which are composed of thin and thick filaments

A

myofilaments

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21
Q

give rise to bands which underlie striations

A

thick and thin filaments

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22
Q

dark and contains thick filaments (mostly myosin)

A

A band

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23
Q

light area at the center of the A band

A

H band

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24
Q

the area where actin and myosin don’t overlap

A

H band

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25
Q

light and contains thin filaments (mostly actin)

A

I band

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26
Q

at the center of I band is ( ), which is where actins attach

A

Z disc/line

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27
Q

contractile units of skeletal muscle consisting of components b/w 2 Z discs

A

sarcomeres

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28
Q

structural proteins that anchor myosin during contraction

A

M line

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29
Q

an elastic protein attaching myosin to Z disc that contributes to elastic recoil of muscle

A

Titin

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30
Q

which ones shorten and why: I, H, or A band

A

I and H bands because they are relatively thin filaments

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31
Q

what is the Sliding Filament Theory of Contraction?

A

the muscle contracts because myofibris get shorter

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32
Q

cross bridges are formed by heads of myosin molecules that extend toward and interact with ( )

A

actin

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33
Q

the sliding of filaments is produced by the actions of ( )

A

cross bridges

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34
Q

Each myosin head (cross bridge) contains an ATP-binding site which functions as an

A

ATPase

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35
Q

Myosin can’t bind to actin unless it is ( )

A

“cocked” by ATP

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36
Q

After binding, myosin undergoes a conformational change (power stroke) which exerts force on ( )

A

actin

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37
Q

what happens after a power stroke?

A

myosin detaches

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38
Q

the control of cross bridge attachment to actin is through what?

A

troponin-topomyosin system

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39
Q

what filament lies in grove between double row of G-actins (which make up actin thin filament)

A

tropomyosin

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40
Q

what is attached to tropomyosin at intervals of every 7 actins?

A

troponin

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41
Q

in relaxed muscle, what blocks binding sites on actin so crossbridges can’t occur?

A

tropomyosin

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42
Q

when does tropomyosin block site on actin so crossbridges can’t occur?

A

when Ca2+ levels are low

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43
Q

Ca2+ levels decrease because it is continually pumped back into the ( )

A

sarcoplastic reticulum

44
Q

calcium reservoir in muscle

A

sarcoplastic reticulum

45
Q

most ca2+ in the SR is in ( )

A

terminal cisternae

46
Q

running along terminal cisternae are ( )

A

T tubules

47
Q

contraction can occur only when ( )

A

binding sites are exposed

48
Q

when Ca2+ levels rise, Ca2+ binds to ( ) causing conformational changes that moves tropomyosin and exposes binding sites

A

troponin

49
Q

Release of Ach at the NMJ causes large depolarizing ( ) and ( ) in the muscle

A

end-plate potentials and APs

50
Q

APs race over the sarcolemma and down into the muscle through

A

T tubules

51
Q

T tubules are extensions of

A

sarcolemma

52
Q

Ca2+ in the SR are mechanically linked to channels in the ( )

A

T tubules

53
Q

APs in the T tubules cause release of Ca2+ from the cisternae through what? what is it called?

A

Voltage gated and Ca2+ release channels—it’s called electromechanical release

54
Q

When APs cease, the muscle relaxes bc Ca2+ channels close and the Ca2+ is pumped back into the SR by ( )

A

Ca2+ ATPase pumps

55
Q

Is ATP needed for relaxation or for contraction?

A

BOTH!

56
Q

a single rapid contraction and relaxation of muscle fibers

A

twitch

57
Q

if a 2nd stimulus occurs before muscle relaxes for 1st, the 2nd twitch will be greater; this is called what?

A

summation

58
Q

contractions of varying strength are obtained by stimulation of varying numbers of fibers

A

graded contractions

59
Q

if a muscles is stimulated by an increasing frequency of electrical shocks, its tension will increase to a maximum

A

incomplete tetanus

60
Q

if the frequency is so fast that no relaxation occurs, a smooth sustained contraction results

A

complete tetanus/tetany

61
Q

if a muscle is repeatedly stimulated with a max voltage to produce individual twitches, successive twithces get larger

A

treppe/staircase effect

62
Q

what is treppe caused by?

A

accumulation of intracellular Ca2+

63
Q

the exerted force does not cause load to move and length of fibers remains constant

A

isometric contraction

64
Q

force remains constant throughout the process

A

isotonic contraction

65
Q

2 ways length changes:

A

1) concentric contraction

2) eccentric contraction

66
Q

Series-Elastic Component

A

tendons and connective tissue are elastic and absorb tension as muscle contracts, and recoil as muscle relaxes and spring back to resting length

67
Q

strength of muscle contraction influenced by:

A

1) frequency of stimulation
2) thickness of each muscle fiber
3) inital length of muscle fiber

68
Q

ideal resting length

A

that which can generate max force

69
Q

if the exercise is moderate, aerobic respiration contributes the majority of the muscle requirements after how long?

A

the first 2 minutes

70
Q

the percentage of VO2max at which there is significant rise in blood lactate levels

A

lactage (anaerobic) threshold

71
Q

during light exercise, most of the energy is derived from

A

aerobic respiration of fatty acids

72
Q

during moderate exercise, energy is derived

A

equally from fatty acids and glucose

73
Q

during heavy exercise, energy is derived

A

2/3 from glucose and liver increased glycogenolysis and the GLUT-4 glucose carrier is moved to muscle cell’s plasma membrane

74
Q

when does O2 debt occur?

A

when O2 is withdrawn from hemoglobin and myoglovin and bc of the O2 needed for metabolism of lactic acid produced by anaerobic respiration

75
Q

a source of high energy phosphate that allows the regeneration of ATP from ADP

A

Phosophocreatine

76
Q

Type I fibers

A

slow-twich, slow-fatigue; slow oxidative

77
Q

type: use mostly aerobic respiration, have rich capillary supply, many mitochondira, and aerobic enzymes

A

Type I

78
Q

type: small motor neurons with small motor units

A

Type I

79
Q

Type IIX fibers

A

fast twitch, fast fatigue; white fast glycolytic

80
Q

type: adapted to contract fast using anaerobic

A

Type IIX

81
Q

type: large stores of glycogen, few capillaries and mitochondria, little myoglobin

A

Type IIX

82
Q

Type IIA

A

fast twitch, fast fatigue; fast oxidative

83
Q

type: intermediate

A

Type IIA

84
Q

sustained muscle contraction fatigue is due to an accumulation of ( )

A

extracellular K+

85
Q

caused by changes in CNS rather than by fatigue in muscles themselves

A

central fatigue

86
Q

the first “wall” an athlete must overcome in endurance exercise

A

central fatigue

87
Q

endurance training improves aerobic capacity by ( ) and lactate threshold by ( )

A

20%; 30%

88
Q

once a myofibril has attained certain thickness, what happens?

A

it may split into two myofibrils

89
Q

allow AP to spread throughout cardiac muscle

A

intercalated disks (gap junctions)

90
Q

has no sarcromeres

A

smooth muscle

91
Q

contains 16X more actin than myosin which allows greater stretching and contracting

A

smooth muscle

92
Q

smooth: actin filaments are anchored to ( )

A

dense bodies

93
Q

smooth: contraction is controlled by Ca2+ but is different from striated muscle in that it ( )

A

has little SR and no troponin/tropomyosin

94
Q

smooth: Ca2+-calmodulin complex activates what?

A

myosin light chain kinase (MLCK)

95
Q

smooth: myosin is dephosphorylated by what and can no longer form cross bridges?

A

myosin phosphatase

96
Q

smooth muscle has slower contractions than striated but can form a state of prolonged binding of myosin to actin called ( )

A

latch state

97
Q

smooth muscle can be divided into:

A

1) single unit

2) multiunit

98
Q

smooth type: spontaneously active (myogenic)

A

single unit

99
Q

smooth type: have gap junctions to spread electrical activity

A

single unit

100
Q

smooth type: some of these cells are pacemakers

A

single unit

101
Q

smooth type: requires nerve stimulation by autonomic nervous system

A

multiunit

102
Q

smooth type: NT is released along a series of synapses called variscosities

A

mulitunit

103
Q

smooth muscle’s variscosities are called ( )

A

synapses en passant

104
Q

smooth type: ex: inestinal and uterine smooth muscles

A

single

105
Q

smooth type: ex: arterial smooth muscle and the ciliary muscles attached to the lens of the eye

A

multi

Human Physiology Block 1 (15 decks)

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