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PHYSL 212 > MUSCLE > Flashcards

MUSCLE Flashcards

1
Q

what does muscle contain

A

contractile proteins

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2
Q

what is the function of muscle

A

convert chemical energy in ATP to sliding of protein filaments

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3
Q

what is muscle specialized for

A

contraction

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4
Q

what are 3 types of muscle cells

A
  1. skeletal
  2. smooth
  3. cardiac
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5
Q

what is skeletal muscle attached to

A

bones

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6
Q

what does contraction of skeletal muscle allow (2)

A
  1. supporting skeleton

2. moving skeleton

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7
Q

what does smooth muscle surround (2)

A
  1. hallow tubes

2. hallow organs

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8
Q

what does contraction of smooth muscle allow

A
  1. propelling contents of hallow tubes + hallow organs

2. regulating diameter of hallow tubes

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9
Q

what does contraction of cardiac muscle allow

A

propelling blood throughout body

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10
Q

what are characteristics of skeletal muscle

A
  1. striated

2. voluntary

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11
Q

what are characteristics of smooth muscle

A
  1. unstriated

2. involuntary

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12
Q

what are characteristics of cardiac muscle

A
  1. striated

2. involuntary

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13
Q

what are 4 functions of muscle

A
  1. move body
  2. manipulate external objects
  3. propel contents through hallow tubes and hallow organs
  4. empty contents to external enviro
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14
Q

what is myocyte

A

muscle cell

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15
Q

what is sarcolemma

A

PM of muscle cell

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16
Q

what is sarcoplasm

A

cyto of muscle cell

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17
Q

what is sarcoplasmic reticulum

A

ER in muscle cell

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18
Q

what is sarcomere

A

contractile unit of muscle

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19
Q

what is muscle fibre

A

single muscle cell

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20
Q

what does skeletal muscle consist of

A

muscle fibres bundled together by CT

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21
Q

how is muscle fibre formed

A

fusion of myoblasts

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22
Q

what are myoblasts

A

cells that are

a. undifferentiated
b. mononucleate

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23
Q

what kind of cell is muscle fibre

A

multinucleate

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24
Q

what are myofibrils made of

A
  • thin filaments

- thick filaments

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25
Q

what are thin and thick filaments made of

A
  • thin ==> actin

- thick ==> myosin

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26
Q

what does motor unit refer to

A

all muscle fibres that single motor nerve innervates

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27
Q

what does number of muscle fibres that single motor nerve innervates depend on

A

dexterity of movement

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28
Q

what does gross movement involve

A

1 nerve innervates hundred of muscle fibres

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29
Q

what does fine movement involve

A

1 nerve innervates 5 to 6 muscle fibres

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30
Q

what is NMJ

A

where motor neuron meets muscle cell

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31
Q

what separates motor neuron from muscle cell

A

synapse

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32
Q

what do synaptic vesicles contain

A

transmitter

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33
Q

where is transmitter released

A

synapse

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34
Q

what is motor end plate

A

area of muscle fibre that is directly under synaptic terminal

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35
Q

what happens at motor end plate

A

motor neuron innervates skeletal muscle

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36
Q

what happens when AP travels down axon of motor neuron

A
  1. synaptic terminal depolarizes
  2. Ca channels opens
  3. Ca rushes into synaptic terminal
  4. vesicles containing Ach migrate to mem
  5. vesicles fuse w mem
  6. vesicles release content into synapse
  7. Ach binds to receptrs on mem of muscle cell at motor end plate
  8. receptors on mem open to allow small amount of Na into muscle cell
    9 small amount of pos charge opens Na channels
  9. large amount of Na enters through Na channels
  10. muscle cell mem depolarizes + AP generates
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37
Q

what is required for skeletal muscle cell to contract

A

stimulation by axon of motor neuron

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38
Q

what does each efferent motor neuron innervate

A

multiple muscle cells

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39
Q

what does motor unit consist of

A
  1. motor neuron

2. all muscle fibres it activates

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40
Q

what does motor unit represent

A

smallest unit of force that can be generated

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41
Q

what is A band

A

dark region with slightly light region in centre

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42
Q

how much of thick filament lies within A band

A

entire width

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43
Q

what is H zone

A

slightly light region in centre of A band

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44
Q

what does H zone contain

A
  1. parts of tick filament

2. none of thin filament

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45
Q

what is M line

A

horizontal line in middle of H zone

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46
Q

what does M line contain

A

system of supporting proteins

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47
Q

what is I band

A

light region

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48
Q

what does I band contain

A

portion of thin filaments that do not project into A band

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49
Q

what is Z line

A

dark horizontal line in middle of I band

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50
Q

what does Z line connect

A

thin filaments of 2 adjacent sarcomeres

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51
Q

what is sarcomere

A
  • distance from Z line to Z line

- smallest functional unit of skeletal muscle

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52
Q

why is sarcomere smallest functional unit of skeletal muscle

A

smallest unit that can contract

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53
Q

what kind of unit is sarcomere

A

repeating unit

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54
Q

what is responsible for striated appearance of skeletal muscle

A

sarcomere

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55
Q

what happens to intracellular Ca levels during excitatory response

A

rise from resting levels

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56
Q

what is actin filament

A

2 strands made of F actin wrapped together to form alpha helix

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57
Q

what is actin associated with

A
  1. tropomyosin

2. troponin

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58
Q

what is troponin composed of

A
  1. troponin T (TnT) ==> binds to tropomyosin
  2. troponin C (TnC) ==> binds to Ca
    3, troponin I (TnI) ==> binds to actin to inhibit contraction
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59
Q

what is tropomyosin composed of

A

2 alpha helices

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60
Q

what is myosin molecule

A

double trimer

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61
Q

what does myosin molecule consist of

A
  • 2 heavy chains
  • 2 regulatory light chains (insides)
  • 2 essential light chains (outsides)
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62
Q

what are 3 regions of heavy chains

A
  1. tail region
  2. hinge region
  3. head region
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63
Q

what region of heavy chain are alpha helices intertwined

A

tail region

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64
Q

what happens to molecule at hinge region

A

unwinds + flares open into 2 globular heads

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65
Q

what does each head of heavy chain form complexes with

A

2 light chains

  • one regulatory light chain
  • one essential light chain
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66
Q

what is function of regulatory light chain

A

regulate ATP ase activity of myosin

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67
Q

what is the function of essential light chain

A

stabilize head region

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68
Q

how are myosin head arranged

A

pointing outwards to leave bare spot in middle

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69
Q

what does myosin head bind

A

actin filament

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70
Q

how do all muscle cells (skeletal, cardiac, smooth) contact

A

cross bridge cycling

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71
Q

where in ATP hydrolyzed in cross bridge cycling

A

at cross bridge

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72
Q

what is energy in ATP converted to in cross bridge cycling

A

small movement

73
Q

what are accessory proteins (4)

A
  1. titin
  2. C protein
  3. alpha actinin
  4. nebulin
74
Q

what is the function of titin

A

anchor thick filaments to Z line

75
Q

what is the function of C protein

A

hold thick filaments in place at M line

76
Q

what is the function of alpha actinin

A

attach thin filaments to Z line

77
Q

what is the function of nebulin

A

anchor thin filament to Z line

78
Q

what is SFT

A

mechanism of muscle contraction

79
Q

what happenes to A band during contraction

A

length remains constant

80
Q

what happens to I band during contraction

A

length changes (i.e. shortens)

81
Q

what happens to sarcomere during contraction

A

length changes (i.e. shortens)

82
Q

what happens to Z lines during contraction

A

move closer together

83
Q

what happens to H zone during contraction

A

gets smaller

84
Q

what does sliding of actin past myosin generate

A

muscle tension

85
Q

how is sarcomere shorted during muscle contraction

A
  • filaments slide past each other

- filaments do not shorten

86
Q

what does cross bridge cycling refer to

A

action of cross bridge (head + hinge region of myosin)

87
Q

what pulls actin towards H zone

A

cross bridges

88
Q

CROSS BRIDGE CYCLING what happens in first step (3)

A
  1. ATP binds to myosin head
  2. myosin reduces affinity for actin
  3. myosin head dissociates from actin
89
Q

CROSS BRIDGE CYCLING what happens in second step (3)

A
  • ATP breaks down to ADP + Pi
  • ADP and Pi stay associated with myosin head
  • myosin head pivots to cocked / resting position perpendicular to actin and myosin filament
90
Q

CROSS BRIDGE CYCLING what happens when myosin head pivots

A

lies up w new G actin monomer

91
Q

CROSS BRIDGE CYCLING what happens in third step (2)

A
  1. myosin head attaches to new G actin monomer

2. ADP and Pi have high affinity for actin

92
Q

CROSS BRIDGE CYCLING what happens in forth step (1)

A
  1. Pi dissociates from myosin head triggering power stroke
93
Q

CROSS BRIDGE CYCLING what happens during power stroke

A
  1. myosin head bends 45 degrees around hinge

2. myosin pulls actin towards tail

94
Q

CROSS BRIDGE CYCLING what happens in fifth step (1)

A
  1. ADP releases from myosin head
95
Q

CROSS BRIDGE CYCLING what happens in attached state

A

myosin (w head bend 45 degrees around hinge) remains attached to actin

96
Q

CROSS BRIDGE CYCLING how long will myosin remain attached to actin

A

until ATP binds

97
Q

RIGOT MORTIS when does rigor mortis develop

A

after death
when there is a lack of
ATP

98
Q

RIGOT MORTIS what happens in rigor mortis

A

myosin head remains attached to actin in attached state

99
Q

RIGOT MORTIS why does myosin head remain attached to actin in rigor mortis

A

lack of ATP

100
Q

when can cross bridge cycling be controlled

A

3rd step

101
Q

what happens when Ca conc less then 10 ^-7

A
  1. inactive cross bridges
    - myosin (w ADP + Pi )cannot bind to actin
  2. muscle relaxes
102
Q

what happens when Ca conc greater than 10 ^-7

A
  1. active cross bridges
    - myosin ADP + Pi can bind to actin
  2. muscle contrats
103
Q

what allows for Ca conc to become greater than 10 ^-7

A

AP

104
Q

what happens at low Ca concentrations

A
  • regulatory proteins (troponin + tropomyosin) inhibit actin -myosin interaction
105
Q

what happens at low Ca concentrations

A
  • Ca binds to regulatory proteins
  • regulatory proteins do not inhibit actin -myosin interaction
  • regulatory proteins undergo conformational change
106
Q

what specifically causes conformational change that allows for actin-myosin interaction and cross bridge cycling

A

Ca binds to TnC of troponin

107
Q

what surrounds myofibrils within muscle fibre

A

SR

108
Q

what does SR contain

A

calcium release channels or ryanodine receptors

109
Q

what does each ryanodine receptor on skeletal muscle contain

A

foot processes

110
Q

what is terminal cisternae

A

enlarged region of SR that stores and releases majority of Ca

111
Q

how is Ca in terminal cisternae stored

A

bound to calsequestrin

112
Q

what is the function of Ca pumps in SR

A

pump Ca from cyto to ST after muscle contraction

113
Q

what are the 2 Ca pumps in SR

A
  1. SERCA 1

2. SERCA 2A

114
Q

what are SERCA 1 and SERCA 2A

A

Ca ATP ase

115
Q

why are SERCA 1 and SERCA 2A Ca ATP ases

A

use en from ATP hydrolysis to pump Ca from cyto to SR

116
Q

how does SR speed up muscle contraction

A

shorter distance from SR to contractile proteins compared to distance from outside of cell to contractile proteins

117
Q

TRANSVERSE TUBULES what are T tubules

A
  1. envaginations of sarcolemma

2. system of ducts that synchronizes release of Ca from terminal cisternae of SR

118
Q

TRANSVERSE TUBULES where do T tubules envaginate

A

junction bw A band and I band

119
Q

TRANSVERSE TUBULES what part of T tubules couples w ryanodine receptors

A

DHP receptors / L type Ca channels

120
Q

TRANSVERSE TUBULES what does couple of T tubules w SR allow

A

AP can be brought into close proximity to SR from T tubule

121
Q

in all 3 muscle types what is intracellular signal that triggers and sustains contraction of msucle

A

increase in intracellular Ca concentration

122
Q

what is triad composed of

A

1 T tubule sandwiched bw 2 SR cisternae

123
Q

what kind of muscle can triads be found

A

skeletal

124
Q

what is dyad composed of

A

1 T tubule next to 1 SR cisternae

125
Q

what kind of muscle can dyads be found

A

cardiac

126
Q

what do triads and dyads play role in

A

coupling excitation and contraction

127
Q

what is equivalent to T tubule system in smooth muscle

A

caveolae

128
Q

what are caveolae

A

rudimentary invaginations of smooth muscle fiber sarcolemma

129
Q

what are carveolae in contact with

A

SR

130
Q

what is “excitation” in coupling referring to

A

excitatory AP

131
Q

what is “ contraction” in coupling referring to

A

contraction of muscle fibre

132
Q

what happens when AP travels from surface mem to T tubule system

A

triad region depolarizes

133
Q

what happens when triad region depolarizes (5)

A
  1. L type Ca channels undergo conformational change
  2. L type Ca channels open
  3. L type Ca channels release Ca from T tubule to cyto
  4. Ryanodine receptors open
  5. SR releases Ca through ryanodine receptors to cyto
134
Q

what allows for ryanodine receptors to open when triad depolarized

A

mechanical coupling w L type Ca channels w foot processes of ryanodine recepotrs

135
Q

what happens when Ca leaves ryanodine receptors

A
  1. Ca binds to troponin
  2. regulatory proteins undergo conformational change
  3. actin-myosin interaction
136
Q

what is involved in Ca removal from intracellular space through PM (2)

A
  1. Na / Ca exchanger (NCX)

2. surface Ca pump (PMA)

137
Q

how does NCX work

A

extrudes 1 Ca from cell in exchange for 3 Na

138
Q

how does PMA work

A

pumps Ca out of cell using ATP hydrolysis

139
Q

why does extrusion of Ca through NCX and PMA play a small role in intracellular Ca removal

A

deplete Ca

140
Q

what is responsible for Ca re-uptake into SR

A

SERCA

141
Q

what is the function of calsequestrin

A
  1. bind to Ca

2. keep Ca lvls low

142
Q

what happens when Ca conc in SR becomes too high

A

inhibits SERCA

143
Q

what does bnding of calsequestrin to Ca allow

A

“keep Ca low” to allow SERCA to continue pumping Ca into SR

144
Q

what is immediate source of energy for muscle contraction

A

ATP

145
Q

how many ATP molecules consumed per 1 round of cross bridge cycling

A

1

146
Q

what is ATP synthesized from

A
  1. lipid metabolism (fatty acids)

2. carb metabolism (glucose)

147
Q

where does most rapid and most readily available pool of energy come from

A

phosphorylation of ADP by creatine phosphate (CrP)

148
Q

what happens during intense exercise

A

fast twitch fibres quickly convert glycogen to ATP

149
Q

how do fast twitch fibres convert glycogen to ARP

A
  1. glycogen broken down into glucose

2. glucose converted to 2ATP + lactic acid

150
Q

what are 2 types of muscle contraction

A
  1. isometric

2. isotonic

151
Q

what happens in isometric contraction

A
  1. length of muscle remains constant
  2. length of sarcomere remains constant
  3. tension developed (by muscle)
152
Q

what is measured during isometric contraction

A

force produced

153
Q

when does isometric contraction occur

A
  1. lifting load that is too heavy

2. pushing load that is too heavy

154
Q

what happens in isotonic contraction

A
  1. length of muscle changes

2. tension remains constant

155
Q

what is measured in isotonic contraction

A

change in length

156
Q

when does isotonic contraction occur

A
  1. lifting load that is not too heavy

2. pushing load that is not too heavy

157
Q

why does tension remain constant during isotonic contraction

A

weight of load being lifted or pushed does not change

158
Q

what is a twitch

A

response of muscle to single AP

159
Q

what happens during twitch

A

contraction phase followed by relaxation phase

160
Q

what is summation

A

second AP fired before giving previous twitch time to fully relax

161
Q

TEMPORAL STIMULATION what does temporal stimulation mean

A

AP s more frequent

162
Q

TEMPORAL STIMULATION what happens during temporal stimulation

A
  • before next twitch tension developed by muscle falls small amount
  • before next twitch muscle has little time to relax
  • built up of tension
163
Q

TEMPORAL STIMULATION why is there a build up of tension

A

there is still residual tension from previous twitch

164
Q

UNFUSED TETANUS what does unfused tetanus mean

A

AP s even more frequent

165
Q

UNFUSED TETANUS what happens during unfused tetanus

A
  • before next twitch tension developed by muscle falls very small amount
  • before next twitch muscle have very little time to relax
  • build up of even more tension
166
Q

TETANUS what does tetanus mean

A

AP s most frequent

167
Q

TETANUS what happens during tetanus

A
  • before next twitch tension developed by muscle does not fall
  • before next twitch muscle has no time to relax
  • build of most tension
168
Q

TETANUS what is tetanus

A

individual muscle twitches become indistinguishable from each other

169
Q

what does it mean if muscle fibres have no time to relax in between AP stimulation

A

no time for Ca to be returned to SR

170
Q

what does not generate force changes in muscle

what does generate force changes in muscle

A

individual fibres // motor units (1 neuron + all muscle fibres it innervates)

171
Q

how are changes in force brought about

A

recruiting more motor units

172
Q

during voluntary contraction what order are motor units activated

A 
1. small (more excitable)
2 large (less excitable)
173
Q

how can tension developed in muscle during contraction be altered

A

altering length of muscle fibre

174
Q

what is optimal muscle length

A

length at which muscle fibre develops greatest isometric tension

100% of muscle length

175
Q

what happens as muscle length increases to 100% muscle length

A

tension increases to 100% isometric tension

176
Q

what happens as muscle length increases past 100% muscle length

A

tension decreases from 100% isometric tension

177
Q

what happens when length is below optimal

A
  • sarcomere not stretched out
  • some myosin unable to interact w correct actin
  • max number of cross bridges not formed
178
Q

what happens when length is at optimal

A
  • sarcomere stretched out
  • all myosin able to interact w correct actin
  • max number of cross bridges formed
179
Q

what happens when length is below optimal

A
  • sarcomere too stretched out
  • some myosin able to interact w correct actin
  • max number of cross bridges not formed

PHYSL 212 (22 decks)

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