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physiology allied health > Unit 3: Muscle Physiology > Flashcards

Unit 3: Muscle Physiology Flashcards

1
Q

3 muscle types

A
  • skeletal
  • cardiac
  • smooth
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2
Q

skeletal muscle classification

A

striated, voluntary

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3
Q

skeletal muscle description

A
  • bundles of long, thick, cylindrical, striated, contracticle, multinucleated cells that extend the length of the muscle
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4
Q

skeletal muscle typical location

A

attached to the bones

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5
Q

skeletal muscle function

A

movement of body in relation to external environment

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6
Q

cardiac muscle classification

A

striated, involuntary

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7
Q

cardiac muscle desrciption

A

interlinked, short, slender, cylindrical, striated, branched, contractile cells connected by intercalated discs

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8
Q

cardiac muscle location

A

heart wall

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9
Q

cardiac muscle function

A

pumping blood out of heart

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10
Q

smooth muscle classification

A

unstriated, involuntary

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11
Q

smooth muscle description

A

loose network of short, slender, spindle-shaped, contractile cells arranged in sheets

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12
Q

smooth muscle typical location

A

walls of hollow organs and tubes (stomach and blood vessels)

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13
Q

smooth muscle function

A

movement of contents within hollow organs

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14
Q

skeletal?

A

a

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15
Q

cardiac?

A

b

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16
Q

smooth?

A

c

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17
Q

skeletal muscle histology

A
  • epimysium
  • endomysium
  • fascicle
  • nuclei
  • muscle fibers
  • blood vessels
  • nerves
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18
Q

skeletal muscle - epimysium

A
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19
Q

skeletal muscle - endomysium

A
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20
Q

skeletal muscle - fascicle

A
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21
Q

skeletal muscle - perimysium

A
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22
Q

skeletal muscle - nuclei

A
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23
Q

skeletal muscle - muscle fibers

A
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24
Q

skeletal muscle - blood vessels and nerves

A
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25
Q

muscle definition

A

group of fascicles

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26
Q

fascicles contain … which …

A

muscle fibers; extend the length of the muscle (tendon to tendon)

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27
Q

which tissue surrounds muscle fibers

A

connective tissue

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28
Q

synctia definition

A

multinucleated

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29
Q

sarcolemma

A

plasma cell membrane that encloses each muscle cell/fiber

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30
Q

endomysium

A

connective tissue that wraps individual muscle fibers

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31
Q

perimysium

A

connective tissue that wraps fascicles

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32
Q

fascicles

A

bundles of muscle fibers

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33
Q

epimysium

A

connective tissue that wraps the who muscle

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34
Q

(deep) fascia

A

a layer of thickened connective tissue that covers the entire muscle and is located over the layer of epimysium

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35
Q

what does skeletal muscle require to contract

A

stimulation by the nervous system

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36
Q

where does the nervous system communicate with the skeletal muscle

A

neuromuscular junction (NMJ)

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37
Q

neuromuscular junction (NMJ)

A
  • impuls travels down the axon of the nerve
  • reaches nmj, chemical transmitter acetylcholine is released
  • muscle contraction
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38
Q

motor unit

A

an axon and muscle fibers it communicates with

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39
Q

what supplies efferent innervation to skeletal muscle

A

efferent arm of the somatic nervous system

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40
Q

motor neuron activity is …

A

cholinergic, nicotinic, and only excitatory

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41
Q

cholinergic definition

A

relating to or denoting nerve cells in which acetylcholine acts as a neurotransmitter.

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42
Q

nicotinic definition

A

related to or imitating the action of nicotine on neurons, esp. in blocking the cholinergic receptors of the autonomic ganglia

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43
Q

NMJ - muscle fiber

A
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44
Q

NMJ - NMJ

A
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45
Q

NMJ - terminal buttons

A
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46
Q

NMJ - axon terminal

A
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47
Q

motor end plate

A

the area of the muscle fiber surface where terminal buttons fit into shallow depressions of the sarcolemma of individual muscle fibers

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48
Q

the cleft

A

the space between the terminal button and the motor end plate

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49
Q

nmj sequence of events

A
  1. action potential in a motor neuron is propagated to the terminal button
  2. ap triggers the opening of voltage-gated Ca2+ channels and entry of Ca2+ into the terminal button
  3. Ca2+ triggers release of acetylcholine by exocytosis from the vesicles
  4. acetylcholine diffuses across the space separating the nerve and muscle cells and binds with receptor-channel specific for it on the motor end plate of the muscle cell membrane
  5. nonspecific cation channels open due to binding leading to large movement of Na+ into the muscle cell and small movement of K+ outward
  6. result is an end-plate potential; local current flow occurs between depolarized end plate and the adjacent membrane
  7. local current flow opens voltage-gated Na+ channels in the adjacent membrane
  8. Na+ entry reduces the potential to threshold initiating an action potential propagated through the muscle fiber
  9. acetylcholine destroyed by acetylcholinesterase terminating the muscle cell’s response
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50
Q

acetylcholinesterase

A

an enzyme on the motor end-plate membrane that destroys acetylcholine

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51
Q

transverse (T) tubules

A

folds of the sarcolemma

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52
Q

sarcoplasm

A

cytoplasm containing myofibrils

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53
Q

sarcoplasmic reticulum

A

smooth ER

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54
Q

skeletal muscle fiber organization

A
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55
Q

skeletal muscle fiber structure

A

regular striated patterns of filaments and organelles hint at functionality

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56
Q

what gives skeletal muscle a striated appearance

A

myofibrils

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57
Q

myofibril definition

A

orderly arrangement of thick and thin filaments (actin and myosin)

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58
Q

what do filaments form

A

sarcomeres

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59
Q

sarcomeres

A
  • function unit
  • z line to z line
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60
Q

myofibril parts

A
  • z line
  • m line
  • a band
  • h zone
  • i band
  • cross bridge
  • thick filaments
  • thin filaments
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61
Q

myofibril - z line

A
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62
Q

myofibril - m line

A
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63
Q

myofibril - a band

A
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64
Q

myofibril - i band

A
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65
Q

myofibril - crossbirdges

A
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66
Q

myofibril - thick filaments

A
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67
Q

myofibril - thin filaments

A
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68
Q

is h zone in myofibril thin filaments, thick filaments, or both?

A

thick filament (myosin) only

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69
Q

is a band in myofibril thin filaments, thick filaments, or both?

A

both

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70
Q

is i band in myofibril thin filaments, thick filaments, or both?

A

thin filament (actin) only

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71
Q

during contraction which part of a myofibril decreases in size due to more thin and thick filaments overlapping?

A

h zone

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72
Q

proteins of the sarcomere

A
  • contractile proteins (actin and myosin)
  • structural proteins (titin, dystrophin)
  • regulatory proteins (troponin-complex, tropomyosin)
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73
Q

types of actin and their purpose

A
  • F(ilamentous) actin is contractile
  • G(lobular) actin has a myosin binding site
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74
Q

tropomyosin

A
  • regulatory protein
  • overlaps binding sites on actin for myosin
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75
Q

troponin-complex

A
  • regulatory protein
  • complex of three proteins [attaches to T(ropomyosin), attaches to I (actin), binds C (calcium) reversibly]
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76
Q

what makes up a thin filament in a sarcomere

A
  • actin
  • tropomyosin
  • troponin
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77
Q

what makes up a thick filament in a sarcomere

A

bundles of myosin molecules bound at the tail

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78
Q

myosin tails point towards what

A

the m line

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79
Q

myosin heads point towards what

A

I band

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80
Q

what is the I band

A

thin filament near Z line

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81
Q

is titin present in thick or thin myofilaments

A

both

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82
Q

titin

A
  • Z line to M line
  • template for myosin assembly
  • supports proteins in muscle
  • anchors thick filaments between M and Z lines
  • structural support and elasticity
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83
Q

parts of a single myosin molecule

A
  • 2 identical myosin heavy chains
  • 4 myosin light chains
  • S1 head segment (ATPase activity, actin binding site)
  • S2 tail segment (flexible hinge regions, combines with other tails)
  • thick filament (contact 6 actin filament)
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84
Q

crossbridge cycle purpose

A

how muscles generate force

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85
Q

excitation-contraction coupling purpose

A

how muscle contractions are turned on and off

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86
Q

muscle cell metabolism

A

how muscle cells provide ATP to drive the crossbridge cycle

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87
Q

at rest, the skeletal muscle …

A

myosin binding sites on actin blocked by tropomyosin

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88
Q

when Ca2+ is present, the skeletal muscle …

A
  • Ca2+ binds to Troponin-complex
  • conformational alteration in Troponin-complex
  • moves tropomyosin
  • exposes myosin binding sites
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89
Q

what does Troponinc C bind to in order to produce a corformational change in Troponin I

A

calcium ions

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90
Q

result of Troponin T binding to tropomyosin

A

troponin-tropomyosin complex

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91
Q

which binding holds the troponin-tropomyosin complex in place

A

troponin I binding to actin

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92
Q

troponin/tropomyosin/actin complex function

A

blocks interaction with myosin

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93
Q

troponin without Ca2+ (relaxed)

A

stabilize tropomyosin actin binding

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94
Q

troponin with Ca2+ (contracting)

A

destabilize tropomyosinactin binding –> cross bridge formation

95
Q

how is a sarcomere shortened

A

z-lines of the extremes of the sarcomeres are pulled in

96
Q

cross bridges and sarcomere shortening includes multiple cycles of

A
  1. actin binding
  2. power stroke
  3. detachment
  4. binding
97
Q

sliding filament mechanism

A
  • muscle contraction
  • needs overlapping of thin and thick filaments
  • neither thin or thick filaments shorten
  • filaments slide past each other
  • sarcomere contraction
98
Q

crossbridge cycle due to…

A

sliding is due to cyclical formation and breaking of cross bridges

99
Q

within a sarcomere during contraction

A
  • a band stays the same length
  • i band shortens
  • h zone shortens
  • sarcomere shortens
100
Q

cross-bridge cycle depends on the presence of either:

101
Q

cross-bridge cycle (ATP)

A
  1. link of thin to thick filaments
  2. power stroke, ADP is released from myosin
  3. myosin binds to new ATP
  4. thick and thin filaments detach
  5. ATP hydrolysis, myosin re-energised
  6. myosin head returns to cocked position
  7. binding again
102
Q

power stroke

A

myosin head moves propelling thin filament toward muscle center

103
Q

cross-bridge cycle (ATP) binding again process

A
  • myosin head returns to initial position
  • myosin head undergoes conformational changes (high and low energy form)
  • relies on ATP hydrolysis
104
Q

excitation-contraction

A

sequence of events where an action potential in the sarcolemma causes contraction

105
Q

excitation-contraction (no calcium)

A
  • troponin holds tropomyosin over myosin binding sites on actin
  • no cross bridges form
  • muscle relaxed
106
Q

excitation-contraction (calcium present)

A
  • binds to troponin
  • causing movement of troponin
  • causing movement of tropomyosin
  • exposing binding sites for myosin on actin
  • cross bridges form
  • cycle occurs, muscle contracts
107
Q

excitation-contraction occurance depends on

A
  • neural input from motor neuron
  • Ca2+ release from the sarcoplasmic reticulum
108
Q

steps from excitation to contraction

A
  1. action potential in sarcolemma
  2. action potential down T tubules
  3. DHP receptors of T tubules open Ca2+ channels in lateral sacs of SR
109
Q

if what continues, the crossbridge cycle continues

110
Q

what pumps calcium back into the sarcoplasmic reticulum

A

sr/er ca2+ ATPase

111
Q

there is a need for a continuous what to maintain a force in a muscle

A

cycle of excitation-contraction

112
Q

dihydropyridine (DHP) receptor

A
  • on t tubules
  • voltage gated
  • opens on depolarization
113
Q

DHP receptors triggers what

A

opening of Ryanodine receptors (RyR) on SR

114
Q

sarcoplasmic reticulum gating steps

A
  1. DHP receptor opens on depolarization
  2. triggers opening of RyR on SR
  3. calcium channels in SR open
  4. calcium released into cytosol
115
Q

excitation to contraction coupling

116
Q

the active generation of mechanical force in muscle is due to

A

interaction between actin and myosin

117
Q

ATP is used by muscles for

A
  1. cross-bridge cycle (splitting ATP by myosin ATPase; binding fresh ATP to myosin for dissociation)
  2. active transport of calcium back into SR (relaxation)
118
Q

sources of ATP

A
  • anaerobic/non-oxidative glycolysis (short term)
  • ATP-CP/creatine phosphate (immediate, anaerobic, lactate buildup)
  • aerobic/oxidative phosphorylation (long-term, O2 needed)
119
Q

creatine phosphate and ATP system

A
  • first source of ATP
  • limited amount, used rapidly (10-30 seconds)
  • provides 4-5 times the amount of ATP present in cells at rest
  • rapid one step process
120
Q

anaerobic/non-oxidative glycolysis

A
  • during intense exercise
  • oxygen supply is limited, anaerobic exercise is primary ATP source
  • O2 absent
  • high intensity exercise (20-120 seconds)
  • only 2 ATP/glucose
  • limited glucose
  • lactic acid build up (burning sensation)
121
Q

oxidative phosphorylation

A
  • primary source for light/moderate exercise (>2 minutes)
  • muscle stores limited amount of glucose as glycogen
  • glucose and fatty acid delivered to muscle by blood
  • dominant after 30 minutes
  • adequate oxygen supply
  • occurs in mitochondria
122
Q

mechanics of skeletal muscle contraction

A
  • the twitch
  • factors affecting generated force by individual muscle fibers
  • force generation regulation by whole muscle
  • length-velocity-load relationships
123
Q

twitch contraction

A
  • contraction produced in a muscle fiber in response to 1 AP
  • all or nothing
  • can be defined for a muscle fiber, motor unit, or whole muscle
124
Q

phases of a muscle twitch

A
  1. latent period (time from AP in muscle to onset of contraction; excitation-contraction coupling)
  2. contraction phase (tension increasing, cross-bridge cycle taking place repeatedly, until apex of an arc)
  3. relaxation phase (tension decreases to zero, longer than phase 2, calcium reuptake)
125
Q

isotonic contraction

A

load remains constant as muscle changes length

126
Q

isometric contraction

A

muscle is prevented from shortening, tension develops at constant muscle length

127
Q

isometric twitch contraction

A
  • length is constant
  • contractile elements generate tension
  • stretches series of elastic elements
  • muscle does not shorten, load not lifted
128
Q

isotonic twitch contraction

A
  • constant tension
  • load lifted as muscle shortens
129
Q

are purely isometric contractions common

130
Q

are purely isotonic contractions common

A
  • no
  • even if a load is constant, isometric precedes isotonic contraction phase
  • as tension increases, isometric contraction continues until tension exceeds the load
  • isotonic contraction then begins
  • tension remains constant as muscle shortens
131
Q

is load constant, why

A

no, load changes as limb position changes

132
Q

isokinetic definition

A

constant speed

133
Q

isotonic and isokinetic contractions can be either … or …

A
  • eccentric
  • concentric
134
Q

the level of force generated by muscle depends on

A
  • factors affecting the force or tension generated by individual muscle fibers
  • regulation of the force/tension generated by the whole muscle
135
Q

factors affecting the force or tension generated by individual muscle fibers

A
  • frequency of stimulation
  • fiber diameter
  • changes in fiber length
  • extent of fatigue
136
Q

recruitment definition

A

numbers of fibers contracting

137
Q

increases in frequency of action potentials in muscle fibers increases tension in which two ways

A
  • treppe
  • summation and tetanus
138
Q

treppe

A

independent twitches follow one another closely, peak tension increases to a constant level

139
Q

cause of treppe

A

unknown, possibly increase in cystolic calcium

140
Q

duration of action potential in an isometric twitch

141
Q

duration of a contraction in an isometric twitch

142
Q

effects of high frequency stimulation in a muscle contraction

A

summation and tetanus

143
Q

label the twitch

144
Q

label the summation

145
Q

label the incomplete tetanus

146
Q

label the complete tetanus

147
Q

cause of summation and tetanus

A
  • tension developed
  • calcium increase in cytosol
  • system saturation (all troponin molecules have calcium bound tp it, crossbridge cycle maces out, max tetanic contractions)
148
Q

amount of tension developed depends on …

A

amount of calcium bounded to troponin

149
Q

force-generating capacity

A

inherent ability of muscle to generate force

150
Q

force-generating capacity depends on

A
  • number of crossbridges in each sarcomere and geometrical sarcomere arrangement
  • more crossbridges per sarcomere = more force
  • more sarcomeres in parallel = more force
151
Q

optimum length in a length-tension relationship

A
  • resting length of muscle at which fibers can develop greatest amount of tension
  • due to maximum overlap of thick and thin filaments
152
Q

non-optimum length in a length-tension relationship

A
  • greater than optimum (decrease crossbridge overlap)
  • less than optimum (thin filaments overlap, Z lines contact thick filaments)
153
Q

muscle definition

A

bundle of muscle fibers

154
Q

more fibers contract = ?

A

greater tension

155
Q

in recruitment of motor units

A
  • activation of motor neuron activates all muscle fibers in the muscle unit
  • increase in tension occurs in steps proportional to size of motor units
156
Q

muscles for delicate movements use ________ motor unites

157
Q

muscles for strength use ________ motor unites

158
Q

are the number of motor unites different in different muscles

159
Q

are small or large motor units recruited first

160
Q

types of muscle fibers in skeletal muscle

A
  • slow oxidative
  • fast oxidative
  • fast glycolic
161
Q

muscle receptors

A
  • muscle spindles
  • golgi tendon organs
162
Q

skeletal muscle fibers are classified according to

A
  • contraction speed
  • primary mode of ATP production
163
Q

skeletal muscle fiber contraction speed is dependent on

A

rate of myosin ATPase activity

164
Q

ATP hydrolysis

A

chemical reaction where a phosphate bond on ATP is broken by water, thereby releasing energy

165
Q

fast skeletal muscle fiber contraction

A

myosin with fast ATPase activity

166
Q

slow skeletal muscle fiber contraction

A

myosin with slow ATPase activity

167
Q

fast fibers __________ and _________ two to three times faster than slow fibers

A

contract; relax

168
Q

slow fiber contractions ______ 10 times longer than fast fibers

169
Q

slow oxidative fiber type is __________ size and force

170
Q

fast oxidative fiber type is __________ size and force

A

intermediate

171
Q

fast glycolytic fiber type is __________ size and force

172
Q

one muscle has a _________ of fiber types, but ….

A

mixture; proportions vary depending on function

173
Q

in single motor units …

A

all muscle fibers are the same type

174
Q

skeletal muscle fiber type recruitment order

A
  • slow oxidative
  • fast oxidative
  • fast glycolytic
175
Q

fatigue

A

decline in a muscle’s ability to maintain a constant contraction force during repetitive stimulation

176
Q

muscle fatigue causes

A
  • low intensity exercise (energy reserve depletion)
  • high intensity exercise (lactic acid build up)
  • strong, sustained contractions (blood vessel compression)
  • very high intensity (depletion of acetylcholine)
  • central fatigue (psychological/neural fatigue)
  • other: build up of inorganic phosphates, ion distribution change
177
Q

neuromuscular fatigue definition

A

depletion of acetylcholine causing fatigue

178
Q

skeletal muscle use adaptations

A
  • no cell division
  • change in muscle size due to change in size of individual cells
179
Q

skeletal muscle disuse atrophy

A

decrease in size (lose myofibrils)

180
Q

skeletal muscle denervation atrophy

A

motor neuron destroyed, no excitation, atrophy due to lack of use

181
Q

skeletal muscle hypertrophy

A
  • increase in size (increase myofibrils)
  • actin and myosin production increase
182
Q

muscle hypertrophy definition

A

increase in muscle size

183
Q

muscle spindle job

A

detect muscle length

184
Q

golgi tendon organ within the tendon job

A

detect muscle tension

185
Q

extrafusal fibers

A
  • conscious control in the muscle
  • muscle contractile cells
  • responsible for skeletal muscle contraction
  • innervated by alpha motor neurons
186
Q

muscle v muscle spindle

A

muscle spindle includes intrafusal fibers

187
Q

intrafusal fibers

A
  • unconscious control
  • adjust sensitivity of muscle sensors to stretch
  • innervated by gamma motor neurons
188
Q

sensory fibers in muscle spindle

A
  • type 1a sensory fibers
  • type 2 sensory ending
189
Q

type 1a sensory fibers

A

annulospiral endings that wrap around the central portion of the spindle

190
Q

type 2 sensory ending

A

flower-spray endings located around either spindle end

191
Q

sensory fiber activity in a stretched muscle

192
Q

sensory fiber activity in a relaxed muscle

A

consistent but neither high or low

193
Q

sensory fiber activity in a contracted muscle

194
Q

monosynaptic reflex loop

A

a reflex arc that provides direct communication between sensory and motor neurons innervating the muscle

195
Q

example of a monosynaptic reflex loop

196
Q

agonist

A

contracting muscle

197
Q

antagonist muscle

A

relaxing or lengthening muscle

198
Q

muscle activation steps

199
Q

golgi tendon organ function

A
  • information on whole muscle tension
  • respond to alterations in muscle tension causing tendon tightening and joint uplifting
200
Q

muscle spindles are ___________ to muscle fibers whereas golgi tendon organs are ___ _______

A

parallel; in series

201
Q

we can feel muscle _________ but not muscle ________

A

tension; length

202
Q

stretch intensity increases ?

A

action potential frequency

203
Q

1b sensory (afferent) axons of golgi tendon organs

A
  • advocates the presence of a more complex multi-synaptic positive/negative feedback in spinal cord
  • 1b pathway to send info to brain through ascending pathways for further processing
204
Q

intrafusal fiber function

A

modulate sensory activity in muscle spindle

205
Q

golgi tendon organs are located in series with ___________ __________ to sense muscle tension

A

extrafusal fibers

206
Q

where is smooth muscle found

A

walls of hollow organs

207
Q

smooth muscle produces …

A

continuous contractions of relatively low force

208
Q

is smooth muscle voluntary or involuntary

A

involuntary

209
Q

what controls smooth muscle

A

nervous system, hormones, and local metabolites

210
Q

smooth muscle cells

A
  • contractile cells
  • uninucleated
  • no troponin
  • dense bodies
  • alow myosin ATPase
  • myosin has light chains
  • little sarcoplasmic reticulum
211
Q

smooth muscle contraction

A
  • no bare portion of myosin
  • acting pulled across longer distances in opposite directions
  • anti-parallel crossbridges
  • contraction requires Ca2+ not troponin
212
Q

smooth muscle classifications

A
  • single unit (visceral)
  • multiunit
213
Q

single unit (visceral) smooth muscle

A
  • contracts as a single unit
  • most common
  • tonic or phasic
  • myogenic (pacemaker or slow wave potentials)
  • digestive, reproductive, urinary tracts, uterus
  • small blood vessels
  • functional synctia
  • linked by gap junctions
214
Q

multiunit smooth muscle

A
  • phasic and neurogenic
  • discrete units function independently
  • walls of large blood vessels, small lung airways, eye muscle, base of hair follicles
  • no gap junctions
  • each functional unit is activated separately (separate innervations)
215
Q

phasic smooth muscle

A

contracts in bursts

216
Q

tonic smooth muscle

A

maintains tone

217
Q

neurogenic

A

initiation of contraction orginated in nervous tissue

218
Q

myogenic

A

initiation of contraction originated in muscle tissue

219
Q

function syncytia

A

a unit of contraction comprised of a network of electrically connected cardiac muscle cells

220
Q

smooth muscle excitation-contraction coupling steps

A

1a. opening of Ca2+ channels in plasma membrane
1b. calcium triggers release of calcium from sarcoplasmis reticulum
2. Ca2+ binds with Calmodulin to form Ca-Calmodulin
3. Ca-Calmodulin activates MLCK (myosin light chain kinase) activation causing myosin phosphorylation
4a. unphosphorylated myosin light chain -> no myosin ATPase activity -> no crossbridge activity
4b. phosphorylated myosin light chain -> myosin ATPase active -> crossbridge coupling -> contraction

221
Q

in skeletal muscle, Ca2+ targets ? via ?

A

actin; troponin/tropomyosin system

222
Q

in smooth muscle, Ca2+ targets ? via ?

A

myosin; calmodulin and MLCK process

223
Q

myosin ATPase is ___ __ ____ __ ________ in smooth muscle compared to skeletal muscle

A

10-100x slower

224
Q

smooth muscle relaxation

A
  1. phosphatase enzyme removes phosphate from myosin
  2. calcium removed from cytoplasm (Ca2+ -ATPase, calcium pumps or Ca2+ -Na+ exchanger)
225
Q

phosphatase is _____________ active and competes with _____ thus ? is needed to activate MLCK

A

continuously; MLCK; high Ca2+ concentration

226
Q

smooth muscle is innervated by …

A

ANS (sympathetic and/or parasympathetic)

227
Q

smooth muscle may be …

A

excitatory or inhibitatory

228
Q

smooth muscle neurotransmitter is released from …

A

varicosities

229
Q

gap junctions function

A

allow electrical signal transmitter from one cell to neighboring cell

230
Q

is smooth muscle able to contract by hormonal/chemical stimulation

231
Q

how is cardiac muscle similar to skeletal muscle

A
  • striated with sarcomeres
  • troponin and tropomyosin regulation
  • T tubules
  • sarcoplasmic reticulum
  • similar to slow oxidative fibers (myoglobin, mitochondria, slow and fatigue resitant)
232
Q

how is cardiac muscle similar to smooth muscle

A
  • gap junctions with intercalated disks
  • pacemaker cells
  • innervated by ANS
  • influenced by hormones, paracrines, adjacent cells
  • Ca2_ from ECF and SR
233
Q

why is there no summation in cardiac muscle

A

long refractory period

234
Q

functional benefit of no cardiac muscle summation

A

summation would not allow the heart to relax after each beat to fill with blood

physiology allied health (6 decks)

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