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S&C > Jan 31st Content > Flashcards

Jan 31st Content Flashcards

1
Q

Muscle classifications

A

skeletal, smooth, cardiac

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2
Q

Characteristics of skeletal muscle

A

multinucleated, has mitochondria, transverse tubules (t-tubules), myofibrils, sarcomeres, intracellular structures (sarcolemma, sarcoplasm, sarcoplasmic reticulum)

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3
Q

Sarcolemma =

A

plasma membrane

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4
Q

Sarcoplasm =

A

cytoplasm

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5
Q

Sarcoplasmic reticulum =

A

smooth ER

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6
Q

What transfers force to the tendon then force to bone resulting in movement?

A

connective tissue

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7
Q

Force produced at the level of the

A

sarcomere

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8
Q

Epimysium

A

surrounds entire muscle

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9
Q

Perimysium

A

middle; surround bundles of muscle fibers

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10
Q

Endomysium

A

surrounds individual muscle fibers

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11
Q

Satellite cells

A

myogenic stem cells located within the sarcolemma

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12
Q

Satellite cells help with

A

regenerative cell growth

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13
Q

Satellite cells may play a role in

A

hypertrophy

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14
Q

Through donation of what do muscle fibers continue to grow

A

nuclei

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15
Q

Structures that give skeletal and cardiac muscle their striated appearance

A

myofibrils

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16
Q

Myofibrils consist of orderly arrangements of

A

actin (thin) & myosin (thick)

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17
Q

Structure of the sarcomere

A

I-band (Z-line, titin), A-band (thin filament, m-line, thick filament), I-band (titin, z-line)

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18
Q

Myofibrils lead to

A

sarcomeres

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19
Q

Tropomyosin is locked onto

A

actin

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20
Q

Troponin is the lock that attaches to

A

tropomyosin

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21
Q

Troponin pulls away when

A

calcium attaches to it

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22
Q

A molecule spring that provides tension

A

Titin

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23
Q

Myofibrils inside

A

endomysium

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24
Q

Myosin filaments are oriented with their trials pointed

A

toward the center of the sarcomere

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25
Q

Proportion of actin to myosin in myofibril =

A

density

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26
Q

Myosin is

A

thick

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27
Q

Actin is

A

thin

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28
Q

Actin consists of

A

tropomyosin and troponin

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29
Q

Skeletal Muscle Mass

A

75% water, 20% protein, 5% other

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30
Q

Arteries and veins lie parallel to

A

individual muscle fibers

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31
Q

Extensive branching of blood vessels ensures each muscle fiber an

A

adequate oxygenated blood supply from the arterial and rapid removal of CO2 in venous circulation

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32
Q

Trained muscle increased capillary to muscle fibers ratio helps explain

A

improved exercise capacity with endurance training

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33
Q

Enhanced capillary microcirculation expedites removal of

A

heat and metabolic byproducts from active tissues in addition to facilitating delivery of oxygen, nutrients, and hormones

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34
Q

Enhanced vascularization at capillary levels proves beneficial during activities that require

A

high level steady-rate aerobic metabolism

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35
Q

Vascular stretch and shear stress on the vessel walls from increased blood flow during exercise stimulates _____________ __________ with ____________ __________ ___________

A

capillary development; intense aerobic training

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36
Q

Capillary to fiber ratio

A

fibers grow more than added capillaries; ratio decreases

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37
Q

Motor units are made up of

A

a motor neuron and the skeletal muscle fibers innervated by the motor neuron’s axon terminals

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38
Q

Groups of motor units work together to

A

coordinate contractions of a single muscle

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39
Q

All motor units within a muscle are considered a

A

motor pool

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40
Q

What moves down the axon arriving at the nerve terminak?

A

action potential

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41
Q

Action potential ________ the nerve terminal

A

depolarizes

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42
Q

Depolarization of the nerve terminal activates

A

voltage-gated calcium channels

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43
Q

Calcium enters the synaptic terminal and increases

A

cytosolic calcium concentration

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44
Q

Increased cytosolic calcium causes release of

A

neurotransmitter from vesicles

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45
Q

Neurotransmitter enters into __________ _________ through ____________

A

synaptic cleft; exocytosis

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46
Q

Neurotransmitter dissociates from receptor and is removed from synpase by (3)

A

metabolism, reuptake into nerve terminal, or diffusion away from synapse

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47
Q

Neurotransmitter =

A

Acetylcholine

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48
Q

Postsynaptic receptor

A

nicotinic-cholinergic receptor (NAChR)

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49
Q

What is nicotinic-cholinergic receptor (NAChR)?

A

a ligand-gated channel

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50
Q

Nicotinic-cholinergic receptor (NAChR) is selective for

A

sodium and potassium

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51
Q

Activation of nicotinic-cholinergic receptor (NAChR) allows

A

diffusion of sodium into the cell and potassium out of the cell

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52
Q

Acetylcholine esterase (AChE) is localized in

A

folds of the endplate

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53
Q

Acetylcholine esterase (AChE) hydrolyses the Ach to

A

choline and acetate

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54
Q

What is taken back into the nerve terminal by sodium dependent co-transporter

A

choline

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55
Q

Choline taken back into the nerve terminal is used to

A

synthesize new Ach

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56
Q

What diffuses away from the synaptic cleft

A

acetate

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57
Q

Acetate is taken up by _______ and enters __________ ___________

A

cells; metabolic pathways

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58
Q

Duration of synaptic transmission

A

1 ms

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59
Q

Only channels present at endplate

A

nicotinic-cholinergic receptor (NAChR)

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60
Q

Endplate is/is not electrically excitable

A

is not

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61
Q

The membrane surrounding the endplate is/is not electrically excitable

A

is

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62
Q

Membrane surrounding the endplate contains

A

voltage-gated sodium and potassium channels

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63
Q

Current produced by EPP spread to surrounding muscle membrane and ________ it to _________

A

depolarized; threshold

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64
Q

Current activates ________________ __________ __________ and produces an

A

voltage-gated sodium channels; action potential

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65
Q

Ratio correspondence of motor neuron action potentials and action potentials in muscle

A

1:1

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66
Q

Voltage-dependent calcium channels (DHP receptors) located in

A

t-tubules

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67
Q

Activation of what channels allows calcium to flow out of the SR into cytoplasm

A

calcium release channels

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68
Q

What is in the SR membrane that pumps cytosolic calcium into the SR

A

calcium ATPase

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69
Q

Action potentials travel down sarcolemma from endplate into the ____________ and activate ___________ __________ ____________

A

t-tubules; voltage-gated calcium channels

70
Q

Activation of voltage gated calcium channels activates

A

calcium release channels

71
Q

Activation of calcium release channels causes release of

A

calcium from lateral sacs of SR

72
Q

Calcium binds to

A

troponin

73
Q

Troponin removes blocking action of

A

tropomyosin

74
Q

Myosin cross-bridge bind to

A

actin

75
Q

Sequestration of calcium into the SR decrease

A

cytosolic calcium concentrations

76
Q

Calcium dissociates from

A

troponin

77
Q

Once calcium dissociates from troponin, what ceases

A

cross-bridge cycling

78
Q

One cross-bridge cycling ceases, the sarcomere

A

extends to resting length

79
Q

Force generation produces shortening of skeletal muscle fiber, overlapping of filaments in each sarcomere, propelled by movements of cross-bridges

A

Sliding filament theory

80
Q

Ability of muscle fiber to generate force and movement depends on

A

interaction of contractile proteins actin and myosin

81
Q

Cross-Bridge Cycle

A
  1. energized cross-bridge binds to actin
  2. phosphate release from myosin for power stroke pulli actin towards center of sarcomere
  3. ATP binds to myosin head causes detach
  4. ATP hydrolyzed into ADP + Pi for new cross-bridge
82
Q

If no ATP available for cross-bridge, it remains

A

attached to actin producing rigor mortis

83
Q

Rigor mortis peaks

A

12 hours after death

84
Q

rigor mortis disappears

A

48-60 hours after death due to breakdown of muscle

85
Q

Regulator proteins

A

tropomyosin and troponin

86
Q

Protein that intertwines with actin and covers myosin binding sites on actin

A

tropomyosin

87
Q

protein binds to tropomyosin and holds it over myosin binding site

A

troponin

88
Q

Subunits of troponin

A

inhibitory, calcium-binding, tropomyosin-binding

89
Q

Calcium-binding sites are on

A

troponin

90
Q

Binding of calcium to calcium-binding sites causes

A

change of troponin to move tropomyosin and expose myosin binding sites on actin

91
Q

Endoplasmic reticulum-like organelles that store calcium in skeletal muscle (and cardiac) muscle fibers

A

sarcoplasmic reticulum (SR)

92
Q

The SR surrounds the

A

myofibrils

93
Q

Enlargements at the end of SR and is associated with the transverse tubule

A

lateral sacs

94
Q

Invaginations of the muscle plasma membrane (sarcolemma)

A

transverse tubules (t-tubules)

95
Q

Activation of motor neuron cell body leads to

A

an action potnetial

96
Q

Action potential at nerve terminal of motor neurons causes release of

A

acetylcholine at neuromuscular junction

97
Q

Acetylcholine activates

A

nicotinic receptors in endplate

98
Q

Activation of nicotinic receptors produces a

A

end-plate potential

99
Q

End-plate potential depolarizes the ____________ ___________ ___________ and produces an _________ ______________

A

surrounding muscle membrane; action potential

100
Q

Action potential propagates to the

A

end of the muscle fiber

101
Q

Action potential enters t-tubule and activates

A

voltage-gated calcium channels (DHP receptors)

102
Q

Calcium is released from sarcoplasmic reticulum via

A

calcium release channels

103
Q

Calcium binds to

A

troponin

104
Q

Tropomyosin moves to uncover

A

myosin binding sites on actin

105
Q

Once myosin binding sites are uncovered

A

cross bridge cycling begins

106
Q

Calcium ATPase pumps calcium back into

A

sarcoplasmic reticulum

107
Q

Once calcium ATPase pumps calcium back to the SR, calcium dissociates from

A

troponin

108
Q

Once calcium dissociates from troponin, tropomyosin

A

covers myosin binding sites and cross bridge cycling ends

109
Q

The plateau and descending limb of the isometric/concentric force-length relationship are well predicted and explained by the amount of

A

overlap between actin and myosin filaments

110
Q

When muscle is stretched while activated and held at a final length long enough for force transients to cease, steady force achieved is higher than steady force developed when muscle is activated while already held isometrically at same final length

A

Residual Force Enhancement

111
Q

Force enhancement after active muscle stretching was maintained when muscles were deactivated

A

Passive Force Enhancement

112
Q

Force enhancement has a passive component and part of that passive components originates in the

A

molecular spring titin

113
Q

Hypothesized that titin is a molecular spring whose stiffness can be regulated by

A

activation and/or force production

114
Q

Titin extends from

A

sarcomere’s z-disc to m-band

115
Q

Titin runs freely in the

A

I-band

116
Q

Titin’s extensibility provdes sarcomeres with

A

passive force

117
Q

Passive force from titin is thought to

A

maintain thick filaments during contraction and provide stability and uniformity to adjacent sarcomeres

118
Q

Structural arrangement of serially aligned spring elements indicates titin’s stiffness can be

A

regulated

119
Q

Skeletal muscles are activated by release of

A

calcium from SR

120
Q

Stretching myofibrils within physiological limits results in

A

higher passive forces in presence of physiological levels of calcium

121
Q

Deactivation of actively stretched myofibrils at an average sarcomere length of 5.0 um resulted in

A

no change in force

122
Q

Passive structures of muscles are ________ and ________ when passively stretched out and become _________ and ___________ during active stretching

A

soft and compliant; hard and stiff

123
Q

Titin forces increase when actin-myosin force

A

decrease

124
Q

When titin is eliminated, all passive and active force transmission across sarcomeres is

A

lost

125
Q

The long axis of a muscle determines the

A

arrangement of individual fibers

126
Q

Differences in sarcomere alignment and length strongly affect a muscle’s

A

force and power generating capacity

127
Q

Fibers run parallel to muscle’s long axis and taper at tendinous attachment

A

fusiform

128
Q

Fan-shaped fiber’s fasciculi lie obliquely

A

pennate

129
Q

Fusiform’s fiber length and fiber force generation transmits directly to

A

tendon

130
Q

Fusiform fiber arrangement facilitates

A

rapid muscle shortening

131
Q

In fusiform, what are equal

A

physiological and anatomical

132
Q

In pennate, anatomical misses

A

some fibers

133
Q

In pennate, physiological contains

A

all fibers

134
Q

Total cross-sectional areas of all fibers within a particular muscle

A

Physiologic Cross Sectional Area

135
Q

How do pennate differ from fusiform?

A

contain shorter fibers, possess more individual fibers, exhibit less range of motion

136
Q

Muscles with greater pennation are slower in _______ _________, and generate greater _________ and __________

A

contractile velocity; force and power

137
Q

Series-fibered muscle features

A

individual fibers that run parallel to muscle’s line of pull

138
Q

Complex parallel arrangement features

A

muscle fibers that terminate in muscle’s midbelly and taper to interact with connective tissue matrix or adjacent fibers

139
Q

Arrangement enables parallel packing of

A

short fibers within a long muscle

140
Q

Force exerted by muscle on object

A

tension

141
Q

Force exerted by object on muscle

A

Load

142
Q

Contraction under conditions in which it develops tension but does not change length

A

isometric

143
Q

Contraction in which muscle changes length while load on muscle remains constant

A

isotonic

144
Q

When tension is greater than load, muscle shortens

A

concentric

145
Q

Load is greater than tension on an unsupported muscle

A

eccentric

146
Q

Contraction of muscle fiber in response to a single action potential

A

twitch

147
Q

Keep length constant and measure tension

A

isometric twitch

148
Q

Keep load constant and measure muscle length

A

isotonic twitch

149
Q

Following action potential, an interval of a few ms known as latent period before tension of muscle fiber begins to increase

A

latency

150
Q

Time interval from beginning of tension development at the end of the latent period to peak tension

A

contraction time

151
Q

The latent period is longer in which twitch

A

isotonic twitch

152
Q

Isometric twitch experiment, twitch tension begins to rise as soon as

A

first cross-bridge attaches

153
Q

Isotonic twitch experiment, the latent period includes both time for ________________________ and extra time to accumulate enough _______________ _________________

A

excitation-contraction coupling; attached cross-bridges

154
Q

Characteristics of isotonic twitch depend upon magnitude of

A

load being lifted

155
Q

At heavier loads

A

latent period is longer, velocity of shortening is slower, duration of twitch is shorter, distance shortened is less

156
Q

Maximum velocity with

A

zero load

157
Q

Zero velocity at

A

maximum load

158
Q

Unloaded shortening velocity is determined by rate at which

A

individual cross-bridges undergo cyclical activity

159
Q

One ATP splits during each cross-bridge cycle, the rate of ATP splitting determines

A

shortening velocity

160
Q

Increasing the load on a cross-bridge slows its forward movement during

A

power stroke

161
Q

If interval between stimuli is long enough for tension to return to baseline, the amplitude of the second twitch will be

A

similar to the first

162
Q

Increases tension due to second stimulus occurring before the tension returns to baseline

A

summation

163
Q

Unfused Tetanus

A

oscillating summated tension

164
Q

Fused Tetanus

A

sustained summated tension

165
Q

Maximal tetanic tension is about _______ the tension of a single twitch

A

5x

166
Q

Tension developed is dependent on

A

overlap of thick and thin filaments

167
Q

Maximal tension occurs when

A

all of the myosin cross bridges can bind to actin

168
Q

As muscle fiber is stretched, fewer cross bridges can bind to actin until no cross bridges can bind, meaning

A

no tension is developed

169
Q

As muscle fiber shortened, thin filaments on one side will interfere with cross bridge formation on opposite side and this will

A

reduce tension developed

170
Q

At very short lengths, the z-lines collide with ends of relatively rigid thick filaments, creating an

A

internal resistance to sarcomere shortening

171
Q

Initial length that produces maximal active tension

A

optimal length

172
Q

Muscles normally operate at plus/minus what % of optimal muscle length

A

30%

S&C (11 decks)

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