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F22 - ANP1105 > 2 - Sept.27&30 - muscles pg. 279-298 & 299-316 > Flashcards

2 - Sept.27&30 - muscles pg. 279-298 & 299-316 Flashcards

1
Q

myo- or mys-

A

muscle

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2
Q

sarco-

A

flesh

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3
Q

muscle fibers

A

to describe skeletal and smooth muscle cells because they are elongated

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4
Q

skeletal muscles are

A

the longest muscle cell, striated and voluntary - can be activated by reflexes

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5
Q

what are skeletal muscles responsible for

A

overall body movement

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6
Q

cardiac muscle constitutes to the —— of the heart walls

A

bulk

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7
Q

cardiac muscle cells are

A

striated, not voluntary

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8
Q

where is smooth muscle found

A

walls of hollow visceral organs like stomach, urinary bladder and respiratory passages

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9
Q

role of smooth muscle

A

to force fluids and other substances through internal body channels

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10
Q

smooth muscle is

A

visceral, non-striated and not voluntary - contractions are slow an sustained

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11
Q

special characteristics of muscle

A

excitability (responsiveness), contractibility, extensibility, elasticity

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12
Q

muscle function

A

producing movement, maintaining posture & body position, stabilizing joints, generating heat

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13
Q

what are striations

A

repeating bands of the proteins actin and myosin that are present along the length of myofibrils

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14
Q

what is the skeletal muscle made up of

A

mainly fibres but also blood vessels, nerve fibres and connective tissue

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15
Q

every skeletal muscle fibres is supplied with what and why

A

never ending, it controls its activity

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16
Q

what Is the general rule for all muscles in terms of blood supply

A

one nerve, one artery, one or more vein for each muscle

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17
Q

muscle cells also give away a lot of

A

metabolic waste

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18
Q

what are the connective sheaths that wrap each individual muscle fibre to keep it intact

A

epimysium, perimysium & fascicles, endomysium

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19
Q

epimysium

A

the overcoat on dense irregular cognitive tissue that surrounds the whole muscle - sometimes blends with deep fascia

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20
Q

perimysium and fascicles

A

each skeletal muscle is grouped into fascicles & surrounding each is a fibrous connective tissue

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21
Q

endomysium

A

wispy sheath of connective tissue that surrounds each individual muscle fibre and consists of fine areolar connective tissue

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22
Q

muscle attachment can be either

A

direct or indirect

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23
Q

direct muscle attachment

A

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

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24
Q

indirect muscle attachment

A

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

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25
Q

what is the purpose for the tendon or aponeurosis in indirect muscle attachment

A

anchors the muscle to the connective tissue covering of a skeletal element (bone or cartilage) or to the fascia of other muscles

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26
Q

what attachments are more common? why?

A

indirect, because they provide durability and are a small size

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27
Q

what are tendons made up of

A

tough connective tissue

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28
Q

tendons are more ideal than fleshy muscle because

A

it’s less fragile, easier to move over a bone and saves space

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29
Q

what does a skeletal muscle look like

A

long-cylindrical with multiple nuclei located beneath its sarcolemma (plasma membrane)

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30
Q

how is each skeletal muscle made (per fibre)

A

through the fusion of hundreds of embryonic cells

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31
Q

sarcoplasm

A

cytoplasm of the muscle cell

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32
Q

what occupies most of the muscle cell volume?

A

myofibril

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33
Q

A sarcomere is a segment of ?

A

myofibril

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34
Q

what are the two types of contractile myofilaments

A

thick & thin

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35
Q

what do thick filaments contain

A

bundled myosin molecules

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36
Q

what do thin filaments contain

A

actin molecules plus other proteins

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37
Q

what do elastic filaments provide?

A

elastic recoil when tension is released and helps maintain organization of myofilaments

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38
Q

how is muscle shortening occur?

A

the thin filament slides past the thick filaments

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39
Q

what are the connective tissue sheaths of skeletal muscle?

A

epimysium, perimysium and endomysium

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40
Q

when muscle fibers contract and pull on the sheaths, wha does this cause/create?

A

a pulling force to the bone to be moved

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41
Q

sarcolemma is the

A

plasma membrane

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42
Q

the sarcoplasm contains a huge amount of

A

glycosomes and myoglobin

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43
Q

glycosomes

A

granules of stored glycogen that provide glucose during muscle cell activity for ATP

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44
Q

Myoglobin

A

red pigment that stores oxygen

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45
Q

what are the 3 specialized structures in a muscle cell?

A

myofibrils, sarcoplasmic reticulum and T-tubules

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46
Q

a single muscle fibers contains hundreds to thousands of

A

myofibrils

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47
Q

myofibrils run —- to the muscle fibre length

A

parallel

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48
Q

myofibrils are made up of a chain of

A

sarcomeres linked end to end

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49
Q

sarcomeres contain even smaller rodlike structures called

A

myofilaments

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50
Q

striations are

A

repeating series of dark and light bands

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51
Q

where are striations located

A

along the length of each myofibril

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52
Q

for an undamaged muscle, which bands are light and dark

A

dark - A bands
light - I bands

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53
Q

each dark A band has a lighter region called ———– located in the ——-

A

H zone, midsection

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54
Q

Each H zone is ——- vertically by a dark line called ——-

A

bisected, M line

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55
Q

how is the M line formed

A

molecules of protein myomesin

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56
Q

each light I band has a midline interruption that is a —— area, called the ——?

A

Darker, Z disc/line

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57
Q

the region of a myofibril between two successive z discs is called a

A

sarcomere

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58
Q

a sarcomere is the

A

smallest contractile unit of a muscle fibre - aka the functional unit of a skeletal muscle

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59
Q

a sarcomere contains an ——- band flanked by half an —— band at each end

A

A, I

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60
Q

With each myofibril, the sarcomeres

A

align end to end like boxcars in a train

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61
Q

myofilaments are the muscle equivalents of

A

the actin-containing microfilaments and myosin motor proteins

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62
Q

what role do the proteins actin and myosin play? Where do these roles reach its highest development?

A

play a role in motility and shape change in most cells in the body; in the contractile muscle fibers

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63
Q

the central thick filaments extend to? and what are they connected in the middle of the sarcomere?

A

the entire length of the A band; the M line

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64
Q

where does the more lateral thin filament extend?

A

across the I band, partway into the A band

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65
Q

What anchors the thin filaments? What is it also known as?

A

Z disc; a protein sheet

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66
Q

Why does the H zone of the A band appear less dense?

A

because think filaments do not extend into this region

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67
Q

why is the M line in the centre of the H zone slightly dark?

A

due to the fine protein strands located there that hold the adjacent thick filaments together

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68
Q

The myofilaments are ——— in alignment at the Z discs and the M lines and are ——– to the sarcolemma at the —— discs

A

Held; anchored; Z

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69
Q

Muscle contraction depends on what?

A

myosin- and actin- myofilaments (thick & thin)

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70
Q

what does each myosin molecule consist of (chemically)

A

6 polypeptide chains: two heavy (aka high-molecular-weight) chains and 4 light chains

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71
Q

What do the heavy chains in a myosin molecule do?

A

twist together to form the myosin ‘rodlike’ tail

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72
Q

how does each heavy chain in a myosin molecule end and what’s it attached to?

A

ends in a globular ‘head’; attached to the tail via flexible hinge

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73
Q

what are the globular heads associated with?

A

each with 2 light chains

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74
Q

The globular heads are the ——- of the myosin?

A

business end

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75
Q

What happens during contraction with the globular heads?

A

they link the thick and thin filaments together, form a cross bridge and swivel around the point of attachment to generate force

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76
Q

How does the myosin itself gathers released energy to drive movement?

A

by splitting into ATP and acts as a ATPase

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77
Q

how many molecules of myosin are in a thick filament

A

300

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78
Q

what forms the central part of the thick filament?

A

the tail

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79
Q

the H zone is considered to be —– because it’s made up of the tail of myosin

A

smooth

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80
Q

Actin has a subunit called

A

globular actin o G actin

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81
Q

each G actin has a ————- to which the myosin heads attach during contraction

A

myosin-binding site (active site)

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82
Q

G acting subunits polymerize into long actin filaments called

A

filamentous or F, actin

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83
Q

what forms the backbone of each thin filament

A

intertwined G actin and F actin

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84
Q

What are the other regulatory proteins located in thin filaments

A

polypeptide stands of tropomyosin and troponin

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85
Q

tropomyosin function in a relaxed muscle fiber (assuming it’s successive - end to end of molecule)

A

block myosin-binding sites on actin so myosin heads on thick filaments don’t bind to the thin filaments

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86
Q

troponin is a globular protein with three polypeptide subunits - what do the 3 subunits do?

A
  1. attacks troponin to actin
  2. brings tropomyosin and helps position it on actin
  3. binds calcium ions
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87
Q

function of troponin and tropomyosin

A

help control the myosin-actin interactions involved in muscle contraction

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88
Q

important proteins for the structure of the myofibril

A

elastic filament and dystrophin

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89
Q

elastic filament is composed of a protein called

A

titin

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90
Q

where does titin extend from and to?

A

from the Z dick to the thick filament, then within the thick filament (also forming its core) to attach to the M line

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91
Q

titan forms the core of what filament & does what for the filament?

A

thick filament; holds it in place, maintaining the A band and helps spring the shape back to normal after stretching

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92
Q

What part of the titin is extensible and unfolding when the muscle stretching and recoils when tension is released?

A

that spans the I band

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93
Q

how does the titin prevent sarcomeres from pulling apart when stretching

A

stiffens as it uncoils to help resist excessive stretching

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94
Q

function of dystrophin

A

links the thin filaments to the integral proteins of the sarcolemma

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95
Q

what are other proteins that bind filaments or sarcomeres together to maintain their alignment

A

Nebulin, myomesin, C proteins

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96
Q

where do Intermediate (desmin) filaments extend to and it’s function?

A

extends from the Z disc and connects each myofibril to the next throughout the width of the muscle cell (horizontally)

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97
Q

Duchenne muscular dystrophy (DMD) is caused by

A

a defective gene for dystrophin

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98
Q

skeletal muscle fibers contain two sets of intracellular tubules that help regulate muscle contraction - what are they called

A

the sarcoplasmic reticulum and T-tubules

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99
Q

Sarcoplasmic reticulum (SR) is

A

an elaborate sloth endoplasmic reticulum

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100
Q

endo-

A

within

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101
Q

Sarcoplasmic reticulum function

A

regulates intracellular levels of ionic calcium by storing it and releasing it when demanded through stimulation for muscle contraction

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102
Q

What provides the final ‘go’ signal for contraction

A

calcium

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103
Q

majority of SR tubules run ——– along the myofibril to ——- with each other at the —– zone

A

longitudinally; communicate; H

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104
Q

terminal cisterns

A

form larger, perpendicular cross channels at the A band-I band junctions and always in pairs

105
Q

what is closely associated with SR that is involved in producing energy used during contraction

A

large numbers of mitochondria and glycogen granules

106
Q

Cross bridges

A

the attachment of myosin with actin within a muscle cell

107
Q

role of ATPase in muscle contraction

A

energy is released during ATP hydrolysis and changes the angle of myosin head - ready to bind to actin if sites are available

108
Q

Where is the T-tubule located

A

at A band - I band junction, just under the sarcolemma - on top f the myofibril

109
Q

T- tubule stands for

A

transverse tubule

110
Q

how does the t-tubule drastically increase the muscle fiber’s surface area

A

the cavity of the tubule is continuous with extracellular space

111
Q

how does the increased surface area from the t-tubule benefit the muscle fiber?

A

allows for changes in membrane potential to rapidly penetrate deep into the muscle fiber

112
Q

along the length, each t-tubule runs between paired terminal cisterns of the SR to form?

A

triads

113
Q

triads are —— groupings of 3 —– structures including ?

A

successive, membraneous; terminal cistern, t-tubule and terminal cistern

114
Q

since t-tubules are continuations of the sarcolemma, they can do what with nerve impulses?

A

conduct impulses to the deepest regions of the muscle cell and every sarcomere

115
Q

what do the impulses trigger?

A

the release of calcium from the adjacent terminal cisterns

116
Q

T-tubule function

A

rapid communication messaging system that ensures every muscle contraction is synchronous from all fibers

117
Q

what acts as voltage sensors for contraction

A

the protruding integral proteins of the t-tubules

118
Q

what forms gated channels, where the terminal cisterns release calcium

A

the integral proteins of the SR

119
Q

contration refers to the

A

activation of myosin’s cross bridges

120
Q

when does literal ‘shortening’ occur in muscle contraction

A

if the cross bridges generate enough tension on the thin filaments to exceed the forces that oppose shortening

121
Q

where does the thin and thick filaments overlap in a relaxed muscle fiber

A

end of the A band

122
Q

during contraction, thin filaments

A

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

123
Q

how does the length of filaments not change during contraction

A

the cross bridge attachments forms and breaks several times during contraction to generate greater tension and thus propelling thin filaments forward

124
Q

knowing how filaments do not lengthen during contraction, what is the last piece of the puzzle that creates muscle cell shortening

A

the event occurs simultaneously in the sarcomere all over the cell

125
Q

at the microscopic level, what things occur as the muscle cell shortens

A
  1. I band shortens
  2. distance between successive Z discs shortens
  3. the H zone disappears
  4. the touching A bands move closer together, without change in length
126
Q

why are the successive Z discs distance between each other shortens?

A

due to the thin filaments sliding centrally, the Z discs are pulled towards the M line since thin filaments are attached to Z discs

127
Q

what is the neurotransmitter that motor neurons use to tell skeletal muscles to contact

A

acetylcholine

128
Q

what are the 4 groups of steps in skeletal muscle contraction

A
  1. event at the neuromuscular junction
  2. muscle fiber excitation
  3. excitation-contraction coupling
  4. cross bridge cycle
129
Q

neuromuscular junctions (motor end plates)

A

specialized chemical synapses formed at the sites where terminal branches of the axon of a motor neuron contact a target muscle cell

130
Q

how many neuromuscular junctions are in each muscle fiber? where is it located?

A

one; midway along its length

131
Q

step one of skeletal muscle contraction - summary

A

the motor neuron releases ACh that stimulates the muscle fiber causing local depolarization

132
Q

end plate potential (EPP)

A

chemically induced change in electric potential of the motor end plate

133
Q

step two of skeletal muscle contraction - summary

A

EPP triggers an action potential that travels across the entire sarcolemma

134
Q

Step 3 of skeletal muscle contraction - summary

A

the action potential in the sarcolemma propagates along t-tubules causing calcium to release from terminal cisterns of SR - Ca is final trigger for contraction

135
Q

what does calcium do in the muscle

A

Ca binds to troponin and causes the myosin-binding sites on actin to be exposed for myosin heads to bind

136
Q

step 4 skeletal muscle contraction - summary

A

the muscle contracts as a result of a repeating cycle of steps hat cause myofilaments to slide relative to each other

137
Q

what are the three steps involved in triggering and then propagating an action potential

A
  1. generation of end plate potential
  2. action potential depolarization
  3. repolarization
138
Q

when EPP occurs, EPP spreads to

A

the adjacent sarcolemma and triggers an AP there

139
Q

after ACh binds to ACh receptors, its effects are quickly terminated by

A

acetylcholinesterase

140
Q

acetylcholinesterase location

A

synaptic cleft

141
Q

acetylcholinesterase function

A

breaks down ACh to its building blocks, acetic acid and choline to prevent continued muscle fiber contraction in absence of addition stimulation

142
Q

Excitation-contraction (E-C) coupling is

A

transmission of AP along the sarcolemma that causes myofilaments to slide

143
Q

E-C coupling occurs when

A

rapid communication between electrical events occurring in the plasma membrane of skeletal muscle fibres and Ca2+ release from the SR, which leads to contraction.

144
Q

troponin binds to —— when levels rise and thus allow for the unblocking of myosin-binding sites on actin

A

calcium

145
Q

the cross bridge cycle repeats and each repetition causes the myosin head to

A

take another ‘step’ by attaching to an actin site further along the thin filament

146
Q

thin filaments continue to slide in cross bridge cycle as long as there’s adequate levels of

A

calcium and ATP

147
Q

muscle tension is

A

the force exerted by a contracting muscle on an object

148
Q

load

A

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

149
Q

what are the two facts of muscle mechanics

A
  1. principles of contraction of a single muscle fiber and a whole skeletal muscle (many fibers) is pretty much the same
  2. muscle tension and load definitions
150
Q

motor unit

A

single nerve cell that supplies nerves to a group of skeletal muscle

151
Q

muscle fibers in a single motor unit are not —— ——- but are —— ——— the muscle

A

clustered together, spread throughout

152
Q

knowing the position of muscle fibers in a single motor unit, what would be the result of stimulation to a singular motor unit?

A

a weak but uniform muscle contration

153
Q

muscle twitch is the

A

response of a muscle to a single stimulation

154
Q

what causes muscle twitches to vary in length between different muscle locations

A

variations in enzymes and metabolic properties of myofibrils

155
Q

graded muscle contractions

A

variations in the degree of muscle contraction by changing either the frequency or strength of the stimulus

156
Q

an increase in frequency of stimulation to muscle causes ——- ——– and the higher the frequency, the ?

A

temporal summation; greater the strength of contraction of a given motor unit

157
Q

an increase in strength of stimulation causes —— , the stronger the stimulation the …?

A

recruitment; more motor units are activated, and the stronger the contraction

158
Q

in the body, the brain determines the strength of muscle’s contraction by changing what?

A

(1) rate of firing AP along the axon of its motor neuron (frequency) and (2) the number of neurons activated (strength)

159
Q

(temporal/wave) summation

A

accumulation of effect especially for muscular, sensory or mental stimuli

160
Q

the second contraction of a muscle is stronger causing summation - why is it stronger?

A

because the muscle was already partially contracted - contraction was added to the previous

161
Q

unfused tetanus

A

degree of wave summation where progression to a sustained but quivering contraction

162
Q

fused tetanus

A

no muscle relaxation and contraction fuses into a smooth, sustained contraction plateau

163
Q

sub threshold stimuli

A

stimuli that produces no observable contraction

164
Q

threshold stimulus

A

the stimulus at which the first observable contraction occurs

165
Q

maximal stimulus

A

strongest stimulus that increases contractile force - all motor units are recruited

166
Q

the recruitment process is not ——— , it is dictated by the —– ——–

A

random; size principle

167
Q

size principle - in any muscle,

A

motor units with the smallest muscle fibers are activated first, then the larger muscle fibers which increase contractile strength and then the largest motor units with the largest muscle fibers are activated when the most powerful contraction is needed

168
Q

prolonging of all muscle contraction due to size principle is important to

A

prevent and or delay fatigue

169
Q

muscle tone

A

when muscles are always slightly contracted to help maintain health and responsiveness to stimuli

170
Q

what are the two main categories of contractions

A

isotonic and isometric

171
Q

isotonic muscle contraction

A

muscle tension that develops overcomes the load and the muscle shortens in length

172
Q

isometric muscle contractions

A

does not always shorten and move a load

173
Q

what Is measured in isometric muscular contractions

A

the increasing muscle tension

174
Q

isometric muscular contractions have no change in —– ——- and a higher amount of ——– and —- —- ——

A

resting length; resistance; peak tension developed

175
Q

isotonic muscular contraction has a decrease in —– —- and a lower amount of —– and — — —- compared to isometric muscular contraction

A

resting length; resistance; peak tension developed

176
Q

what are the two sub categories of isotonic contractions

A

concentric and eccentric

177
Q

concentric contractions

A

the muscle shortens and does work

178
Q

eccentric contractions

A

the muscle generates force as it lengthens

179
Q

eccentric contractions are still equally important as concentric contractions for

A

coordination and purposeful movements

180
Q

which contractions is 50% more forceful than the other

A

eccentric

181
Q

when do muscles isometrically contract

A

when they’re primarily used to maintain upright posture or hold joints stationary while other move

182
Q

what event in the muscle is identical in both isotonic and isometric contractions but the results are not

A

the electrochemical and mechanical events

183
Q

thin filaments in isometric contractions ———- move even through the cross bridges generates force

A

do not

184
Q

What is the only energy source directly used for muscle contraction

A

ATP

185
Q

what are the three pathways for regenerating ATP during muscle activity

A

direct phosphorylation, anaerobic pathway and aerobic pathway

186
Q

what pathway of regenerating ATP during contraction requires oxygen?

A

aerobic

187
Q

what is the approximate length of energy from each of the 3 pathways of regenerating ATP?

A

Direct phos - 15 sec
anaerobic - 40 sec
aerobic - several hours

188
Q

what is the slowest and fastest ATP regeneration pathway?

A

aerobic and direct phosphorylation

189
Q

what is an alternative compound that is a source of energy for muscle tissue

A

creatine phosphate

190
Q

muscle cells store 2-3 time more —– than ATP?

A

creatine phosphate

191
Q

creatine kinase

A

enzyme that catalyzes the transfer of phosphate from CP to ADP to create ATP

192
Q

aerobic endurance

A

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

193
Q

anaerobic threshold

A

the point where the muscle metabolism converts to anaerobic glycolysis

194
Q

muscle fatigue

A

physiological inability to contract a muscle even though it’s receiving stimuli

195
Q

what does muscle fatigue prevent?

A

complete depletion of ATP in muscle

196
Q

what chemical changes are involved in muscle fatigue?

A

ionic imbalances, increased inorganic phosphate and magnesium, decreased ATP and glycogen

197
Q

what does ionic imbalances in the muscle do to stop muscle contraction?

A

inhibits action potential which reduces movement to voltage sensitive proteins in T tubules and thus reducing Ca released from SR

198
Q

excess post exercise oxygen consumption

A

the volume of oxygen required after exercise to replenish stores of oxygen, ATP, creatine phosphate, glycogen and oxidize the lactic acid that has formed

199
Q

the force of muscle contraction depends on

A

the number of myosin cross bridges that are attached to actin

200
Q

what’s are the four factors that increase the force of skeletal muscle contraction

A
  1. high frequency of stimulation
  2. large number of recruited muscle fibers (=more motor units used)
  3. large muscle fibers
  4. muscle & sarcomere being stretched slightly over 100% of resting length
201
Q

where does muscle generate maximum force between of it’s optimal resting length?

A

80-120%

202
Q

what factors influence velocity and duration of skeletal muscle contraction?

A

muscle fiber type, load and recruitment

203
Q

two functional characteristics of muscle fiber types

A

speed of contraction and major pathways for forming ATP

204
Q

velocity of fiber shortening consists of two groups, slow and fast fibers. What is the general difference between the two reflect?

A

how fast their myosin ATPases split ATP; pattern of electricity of motor neuron; how fast calcium moves into SR

205
Q

knowing the two functional criteria for classifying types of muscle fibers- what are the different skeletal muscle cell groups?

A

slow oxidative fibers, fast oxidative fibers and fast glycolytic fibers

206
Q

How many types of fiber muscle would all muscle fibers in a particular motor unit have?

A

one - all the same type

207
Q

what does a greater load result in? (duration & velocity)

A

longer latent period, slower shortening and briefer duration of shortening

208
Q

Aerobic (endurance) exercises result in what changes in the skeletal muscles?

A

increased number of capillaries and mitochondria in muscle fiber and fibers synthesize more myoglobin

209
Q

in what type of fiber is aerobic exercise benefits seen the most?

A

slow oxidative fibers

210
Q

what type of exercise promotes muscle hypertrophy?

A

high-intensity resistance especially under anaerobic conditions

211
Q

what are the two sheets of smooth muscle?

A

longitudinal layer and circular layer

212
Q

What are the differences smooth muscle fibers have in contrast to skeletal muscles? (smooth muscle…)

A
  1. is small spindle-shaped cells
  2. lacks the coarse connective tissue sheaths
  3. has varicosites instead of neuromuscular junctions
    4.has less elaborate SR and no T-tubules
  4. usually electrically connected by gap junctions
213
Q

Varicosities

A

knoblike swellings of certain autonomic axons containing mitochondria and synaptic vesicles

214
Q

what do varicosities do for smooth muscle?

A

form diffuse junctions that sprinkle neurotransmitters in the general area of SM cells

215
Q

Caveloae description and function

A

pouch like inholdings containing large numbers of calcium channels; major source of calcium for smooth muscle contraction

216
Q

no striations in smooth muscle, meaning there’s no?

A

sarcomeres

217
Q

how does the proportion and organization of smooth muscle myofilaments differ from skeletal muscle?

A
  1. less thick filaments, but myosin heads are along the entire length
  2. no troponin complex in thin filaments
  3. contains non contractile intermediate filaments to resist tension
  4. thick and thin filaments are diagonally
218
Q

The intermediate filament–dense body network forms a strong, cable-like intracellular cytoskeleton that?

A

harnesses the pull generated by the sliding of the thick and thin filaments

219
Q

what do gap junctions connect in smooth muscle?

A

adjacent fibers

220
Q

what differentiates smooth muscle in different body organs?

A
  1. fiber arrangement and organization
  2. innervation
  3. responsiveness to various stimuli
221
Q

what are the two major types of smooth muscle?

A

unitary and multi unit

222
Q

unitary smooth muscle is also called

A

visceral muscle

223
Q

location of unitary smooth muscle & commonality

A

in the walls of all hollow organs except the heart & is far more common

224
Q

unitary smooth muscle characteristics

A
  1. arranged in opposing sheets
  2. innervated by varicosities of automotive nerve fibers
  3. exhibit rhythmic spontaneous action potentials
  4. are electrically coupled by gap junctions and contract as a unit
  5. respond to various chemical stimuli
225
Q

multi-unit smooth muscle example locations

A

large airways to lungs, large arteries, internal eye muscles

226
Q

what is absent in multi-unit smooth muscle that is present in unitary smooth muscle?

A

gap junctions and spontaneous depolarizations

227
Q

like skeletal muscle, multi-unit smooth muscle

A
  1. consists of muscle fibers that are structurally independent of one another
  2. richly supplied with nerve endings which is formed with a motor unit
  3. responds to neural stimulation with graded contractions that involve recruitment
228
Q

unitary and multi-unit smooth muscles both served and respond to, that skeletal muscles do not

A

innervated by autonomic (involuntary) nervous system division and respond to hormones

229
Q

what are the 2 special features of smooth muscle contraction that differs from skeletal muscles? & explain.

A
  1. response to stretch; SM spontaneously contracts when stretched to allow substance movement
  2. length and tension changes; SM stretches more and generates more tension than skeletal due to irregular filament arrangement and lack of sarcomeres
230
Q

What is the purpose of smooth muscle 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

231
Q

what does the stress-relaxation response look like in smooth muscle?

A

when stretched, it contracts but the tension is brief and then the muscle relaxes and adapts to the new length

232
Q

what are some other unique characteristics of smooth muscle?

A

smooth muscle tone, slow prolonged contractions and low energy requirements

233
Q

what are some ways smooth muscle contraction is regulated?

A

by nerves, hormones or local chemical changes

234
Q

what does the effect of a specific neurotransmitter on a smooth muscle cell depend on?

A

type of receptor molecules on the cell’s sarcolemma

235
Q

Some smooth muscle layers have no nerve supply at all, so how do they respond to chemical factors?

A

they depolarize spontaneously or in response to chemical stimuli that bind to G protein-linked receptors

236
Q

what are some chemical factors that cause smooth muscle to contract or relax without action potential by inhibiting or enhancing calcium entry into sarcoplasm?

A

certain hormones, histamine, excess CO2, low pH and lack of O2

237
Q

smooth muscle takes —– times longer to contract and relax than skeletal muscle, yet it can maintain the same contractile tension for prolonged periods at less than —% of the energy cost

A

30; 1

238
Q

smooth muscle tone

A

moderate degree of contraction all the time without fatiguing

239
Q

what is part of the striking energy economy of smooth muscle?

A

sluggishness of its ATPases and myofilaments may latch together during prolonged contractions (which saves energy)

240
Q

Smooth muscle contraction responds in unison. What is the synchronization reflecting?

A

electrical coupling of smooth muscle cells by gap junctions that transmit depolarization to each fiber

241
Q

purpose of pacemaker cells

A

once excited, they set the pace of contraction for the entire muscle sheet

242
Q

what can modify the rate and intensity of smooth muscle contraction

A

neural and chemical stimuli

243
Q

what happens to pacemaker cells when there’s an absence of external stimuli?

A

depolarize spontaneously

244
Q

smooth muscle contraction is similar to skeletal muscle contraction in what ways?

A
  1. calcium ion level is the final trigger for contraction
  2. actin and myosin interact by the sliding filament mechanism
  3. ATP energizes the sliding process
245
Q

calmodulin

A

a cytoplasmic calcium-binding protein

246
Q

how does calcium activate myosin in smooth muscle contraction?

A

by interacting with calmodulin

247
Q

what does calmodulin do after calcium activates myosin?

A

interacts with myosin light chain kinase or myosin kinase to phosphorylates the myosin and in turn activiating it

248
Q

what is part of the process for stopping smooth muscle contraction

A

calcium detachment from calmodulin; active transport of calcium into SR and extracellular fluid; dephosphorylation of myosin by a phosphate enzyme (reducing myosin ATPase activity)

249
Q

with rare exceptions from what cell do all three types of muscle tissues develop from?

A

myoblasts

250
Q

in skeletal muscle formation, several myoblasts fuse to form?

A

multinuclear myotubes

251
Q

how is the number of fast and slow contractile fiber types determined during development?

A

by the nerves that innervate them

252
Q

myoblasts producing cardiac and smooth muscle cells do not fuse but instead develop what?

A

gap junctions early in embryonic stages

253
Q

satellite cells

A

myoblast-like cells associated with skeletal muscles, that help retain injured fibers and allow limited regeneration of dead skeletal muscle

254
Q

how do heart muscles repair?

A

mainly by scar tissue

255
Q

smooth muscle blood vessels divide how often?

A

regularly throughout life

256
Q

both skeletal muscle and cardiac muscles can retain what ability in a growing child and in adults?

A

ability to lengthen and thicken in child; hyptertrophy in load response in adults

257
Q

what hormone is responsible for hypertrophy?

A

testosterone

258
Q

what is a preventative and can show disease reversal when done daily to help maintain healthy muscles?

A

exercise

F22 - ANP1105 (11 decks)

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