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BIOL 336 > L13, 14 & 15: Muscle Physiology > Flashcards

L13, 14 & 15: Muscle Physiology Flashcards

1
Q

three types of muscle?

A

skeletal, cardiac, smooth

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2
Q

skeletal properties?

A

multinucleate, unbranched, voluntary activity

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3
Q

cardiac properties?

A

1 or 2 nuclei, branched, non-voluntary

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4
Q

smooth

A

single nucleus, unbranched, non-voluntary

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5
Q

skeletal muscles are connected

A

to at least two bones

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6
Q

an exception of the two-bone rule

A

biceps

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7
Q

muscles are connected to bones with

A

tendons, connective elastic tissue

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8
Q

muscle bodies are covered by

A

epimysium

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9
Q

muscle bodies are divided into

A

fascicles

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10
Q

fascicles are covered by

A

perimysium

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11
Q

fascicles contain

A

muscle fibers

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12
Q

muscle fibers are covered by

A

endomysium

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13
Q

a muscle fiber semifluid cytoplasm

A

sarcoplasm

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14
Q

contractile machinery in sarcoplasm

A

myofibrils

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15
Q

plasma membrane of a musle fiber

A

sarcolemma

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16
Q

surrounds each myofibril

A

sarcoplasmic reticulum

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17
Q

fundamental unit of myofibril

A

sarcomere

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18
Q

sarcomere elements

A

a band, i band, z line, m line, h zone

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19
Q

z line

A

end of sarcomere, links thin filaments

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20
Q

m line

A

middle of sarcomere, links thick filaments

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21
Q

i band

A

thin filaments only

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22
Q

h zone

A

thick filaments only

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23
Q

a band

A

thick filaments + overlap

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24
Q

which band is dark?

A

a band

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25
Q

which band is light?

A

i band

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26
Q

myosin parts

A

head, neck, tail

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27
Q

myosin types

A

myosin I inside the cell, myosin II in muscles

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28
Q

muscle contracts by

A

a sliding filament mechanism

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29
Q

cross-bridge steps

A

cross-bridge formation, power stroke, cross-bridge detachment, reactivation of myosin

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30
Q

cross-bridge formation?

A

activated myosin head with ADP and Pi binds to actin site, then Pi is released, the bond becomes stronger

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31
Q

power stroke?

A

ADP is released, sliding microfilament due to pivoting of the head

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32
Q

cross-bridge detachment?

A

ATP binds the head, the actin-myosin bond weakens, myosin head detaches

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33
Q

you got this!

A

you got this!

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34
Q

reactivation of myosin?

A

ATP is hydrolyzed to ADP and Pi, the energy activates the head, moves to the cocked position

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35
Q

does the H zone length change due contraction?

A

yes

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36
Q

does the Z distance change due to the contraction?

A

yes

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37
Q

does the A band length changes due to the contraction?

A

no

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38
Q

does the I band length change due to contraction?

A

yes

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39
Q

tropomyosin is

A

a rod-shaped protein, overlaps 7 actin monomers, covering myosin-binding sites

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40
Q

troponin is

A

a 3 subunit protein with TnC subunit doing Ca2+ binding

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41
Q

what causes uncovering of myosin-binding sites?

A

Ca2+ to TnC of troponin results in a conformational change of tropomyosin

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42
Q

what works together to coordinate contraction

A

transverse (t-)tubules and sarcoplasmic reticulum

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43
Q

what carries electrical information in muscle fibers?

A

by T-tubules

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44
Q

what releases calcium?

A

sarcoplasmic reticulum

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45
Q

muscle contraction step 1

A

action potential stimulates the muscle

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46
Q

muscle contraction step 2

A

muscle action potential goes to the T-tubule

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47
Q

muscle contraction step 3

A

t-tubules make SER release Ca2+

48
Q

muscle contraction step 4

A

ATP and Ca2+ are required for thick-thin filament

49
Q

muscle contraction step 5

A

electrical potential returns to normal, Ca2+ is pumped back to SER by Ca2+ pump proteins

50
Q

what releases Ca2+ ions into the cytoplasm from SER

A

ryanodine receptors

51
Q

what activates ryanodine receptors

A

voltage-gated protein, dihydropyridine (DHP) receptor in the T-tubule membrane

52
Q

what triggers the DHP receptor?

A

muscle action potential

53
Q

the only mechanism to stimulate an action potential

A

activation of motor neuron

54
Q

motor neurons are located in

A

ventral horn

55
Q

motor neuron axons are

A

myelinated and largest diameter

56
Q

do motor neurons have a delay?

A

no

57
Q

motor unit

A

motor neuron plus all muscle fiber it innervates

58
Q

neuromuscular junction

A

junction of an axon terminal with the muscle fiber plasma membrane

59
Q

the first major difference between interneuronal synapses and NMJs

A

a single depolarization of motor endplate is much larger

60
Q

why is the depolarization of NMJ is larger than of interneuronal synapse?

A

larger area, more N-AChRs

61
Q

second major difference between interneuronal synapses and NMJs

A

no inhibitory potentials in NMJs

62
Q

tubocurarine

A

nondepolarizing neuromuscular blocking agent, antagonists, relaxes muscles

63
Q

nicotine

A

N-ACh-R agonist

64
Q

muscarine

A

M-ACh-R agonist

65
Q

atropine

A

M-ACh-R antagonist

66
Q

isometric contraction

A

no shortening, static

67
Q

isotonic contraction

A

change of length, dynamic

68
Q

concentratic contraction

A

tension > load, result

69
Q

eccentric contraction

A

load > tension, no result

70
Q

latent period

A

onset of contraction, few msec

71
Q

contraction phase

A

tension increasing, 10-100 msec, calcium levels increases, release exceeds reuptake

72
Q

relaxation phase

A

tension decreasing, long, cytosolic calcium levels decrease, reuptake exceeds release

73
Q

types of isotonic contraction

A

concentric, eccentric

74
Q

as load increases, plateau times

A

decreases

75
Q

as load increases, latent period

A

increases

76
Q

eventually, isotonic movement becomes

A

isometric

77
Q

summation

A

increase in muscle tension from successive action potentials

78
Q

unfused tetanus

A

at low stimulation frequencies, the tension may oscillate as the fiber partially relaxes between stimuli

79
Q

fused tetanus

A

at higher stimulation frequencies tension does not oscillate, it becomes 3-5 times greater than isotonic twitch

80
Q

twitch

A

same tension over a period of time

81
Q

during tetanus, Ca2+ concentration

A

persistently elevated

82
Q

the magnitude of active tension depends on

A

muscle fiber length

83
Q

shorter than optimum length

A

thin filaments overlap, causing a decline in tension

84
Q

beyond optimum length

A

decreased overlap between thin and thick filaments, no binding of myosin heads to actin

85
Q

ATP is used in the skeletal muscle to… reason 1

A

dissociate myosin heads from actin

86
Q

ATP is used in the skeletal muscle to… reason 2

A

energize the myosin heads when hydrolyzed

87
Q

ATP is used in the skeletal muscle to… reason 3

A

lower cytosolic Ca2+ levels via Ca2+ pump in the SER

88
Q

ATP is used in the skeletal muscle to… reason 4

A

restore ions that cross the cell membrane to their original compartment the Na+ K+ ATPase

89
Q

three ways of ATP formation

A

phophorylation of ADP by creatine phosphate, glycolysis, oxidative phosphorylation

90
Q

fatigue

A

muscle is no longer able to generate or sustain the expected power output

91
Q

fatigue depends on

A

intensity and duration of activity, metabolism, muscle composition, fitness level

92
Q

two types of fatigue

A

central and peripheral

93
Q

_ fatigue comes before physiological fatigue

A

phychological

94
Q

central fatigue

A

changes proximal to motor neuron, motivation, recruitment

95
Q

peripheral fatigue

A

motor unit itself, exhaustion of muscle energy supplies

96
Q

high-frequency fatigue

A

fast fatigue, fast rest period

97
Q

low-frequency

A

long duration, long rest period

98
Q

extended submaximal exertion

A

depletion of glycogen stores, decreased Ca2+ release

99
Q

short-duration maximal exertion

A

increased level of inorganic phosphate, altered power stroke

100
Q

maximal exercise

A

K+ rise in the t-tubule ECF, altering the muscle fiber membrane potential

101
Q

muscle fibers are classified on the basis of

A

maximal velocities of shortening and the major pathway used to form ATP

102
Q

high ATPase activity

A

fast and type II fibers

103
Q

low ATPase activity

A

slow and type I fibers

104
Q

major pathways to form ATP

A

oxidative and glycolytic

105
Q

oxidate fibers have lots of

A

myoglobin

106
Q

myoglobin

A

oxygen-binding protein, gives fibers dark red color

107
Q

fiber with glycolytic enzymes

A

white muscle fibers

108
Q

three principal types of skeletal muscle fibers

A

slow-oxidative (type I), fast-oxidative glycolytic fibers (type IIa), fast-glycolytic fibers (type IIb)

109
Q

type I fibers description

A

low myosin ATPase activity, high oxidative capacity

110
Q

type IIa fibers description

A

high myosin ATPase activity, high oxidative capacity, intermediate glycolytic capacity

111
Q

type IIb fibers description

A

high myosin ATPase activity with high glycolytic capacity

112
Q

type I fatigue?

A

resistant to fatigue, maintain long periods of contractile activity

113
Q

type IIa fatigue?

A

intermediate capacity to resist fatigue

114
Q

type IIb

A

fatigue rapidly

115
Q

singe motor unit is composed of

A

single fiber type

116
Q

recruitment order

A

first type IIb, then type IIa, then type I

BIOL 336 (20 decks)

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