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Biol 1190 > lecture 10 > Flashcards

lecture 10 Flashcards

1
Q

3 types of muscular tissue and their functions

A

skeletal - contracts to move bones and stabilize body

cardiac - contacts to move blood blood through heart

smooth - contracts to regulate passage of substances through the body

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2
Q

myology

A

study of muscular tissue

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3
Q

4 properties of muscular tissue

A
  1. electrically excitable
  2. contractile
  3. extensible
  4. elastic
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4
Q

electrically excitable - property

A

muscle can produce electric signals called muscle action potentials

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5
Q

contractile - property

A

muscle action potentials stimulate contraction

contraction generates tension on bones which causes movement

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6
Q

extensible - property

A

tissue can be stretched without tearing

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7
Q

elastic - property

A

resting length is restored after stretching

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8
Q

difference between extensible and elastic properties (dont mix them up)

A

elastic - resting length RESTORED after stretching
extensible - can BE STRETCHED

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9
Q

cells of skeletal muscle tissue

A

myocytes

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10
Q

what do myocytes contain?

A

myofibrils

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11
Q

muscle (organ) is made up of (3)

A

muscle fibres
connective tissue
nerve and blood supply

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12
Q

fascia

A

connective tissue layers that surround muscles

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13
Q

fascia functions

A

group muscles with similar function

provide passage for nerves and vessels

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14
Q

3 layers of the fascia (superficial to deep)

A

epimysium
perimysium
endomysium

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15
Q

epimysium (what is it and what is it made of)

A

most superficial layer of fascia

dense irregular CT that wraps muscles

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16
Q

perimysium (what is it + made of)

A

intermediate layer of fascia

dense irregular CT that wraps fascicles

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17
Q

fascicles

A

bundles of muscle fibres (Cells)

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18
Q

endomysium (what is it + made of)

A

deepest layer of fascia

mostly reticular fibres that wrap individual muscle fibres

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19
Q

layers of muscle (superficial to deep) (7)

A

epimysium wraps:
muscle
perimysium wraps:
fascicles
endomysium wraps:
muscle fibres which contain:
myofibrils

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20
Q

fascia form:

A

tendons

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21
Q

tendons

A

connect muscle to bone via a rope like structure

made of epimysium (dense irregular CT)

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22
Q

aponeuroses

A

special type of tendon that forms a sheet
(eg. epicranial apoenurosis, connects bellies of occipitofrontalis)

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23
Q

why must muscle be extremely vascularized?

A

muscles preform aerobic cellular respiration which makes ATP

aerobic = required oxygen continuously

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24
Q

myoblasts

A

immature muscle cells in the womb, as they mature, they fuse and create multinucleate cells

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25
Q

plasma membrane of myocytes

A

sarcolemma

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26
Q

T tubules

A

invaginations of the sarcolemma

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27
Q

cytoplasm of myocytes (and what it is rich in)

A

sarcoplasm

rich in glycogen

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28
Q

myoglobin

A

only found in muscle cells
binds O2 at heme
receive O2 from in and outside the cell

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29
Q

myofibrils

A

long threads of contractile protein filaments called myofilaments

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30
Q

what gives muscle striated appearance?

A

pattern of overlapping filaments

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31
Q

sarcoplasmic reticulum

A

specialized SER in muscle cells
stores/releases calcium
folded around each myofibril

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32
Q

triad

A

where a terminal cisternae meets a T tubule

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33
Q

terminal cisternae

A

release Ca2+ to each t tubule

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34
Q

muscle hypertrophy

A

increase in sarcoplasmic volume

each fibre increases volume of cellular contents, mainly myofibrils, mitochondria, and SR

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35
Q

each myofilament is made of contractile units called:

A

sarcomeres

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36
Q

sarcomere

A

consists of overlapping thick and thin filaments

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37
Q

all zones and lines of a sarcomere (listed) (5)

A

I band
Z disc
H zone
A band
M line

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38
Q

A band

A

where tick and thin filaments overlap, and everything in between

covers most of the sarcomere

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39
Q

H zone

A

regions BETWEEN the zones of overlap of thick and thin filaments

goes from ends of thin filaments and crosses M line

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40
Q

I band

A

regions between zones of overlap and Z discs

spans over 2 sarcomeres

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41
Q

M line

A

Mid line of the sarcomere

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42
Q

Z disc

A

jagged lines that divide sarcomeres

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43
Q

three types of proteins involved in muscle contraction

A

contractile proteins
regulatory proteins
structural proteins

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44
Q

contractile proteins (2)

A

work to shorten the sarcomere

myosin - thick filaments
actin - thin filaments

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45
Q

myosin (4)

A
  • a motor protein - contractile
  • makes up thick filaments in sarcomere - 300 each ish
  • has heads that extend and contact thin filaments
  • converts chemical potential energy in ATP to mechanical energy
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46
Q

myosin head binding sites

A

top - actin binding site
side - ATP binding site

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47
Q

actin (3)

A
  • cytoskeletal protein - contractile
  • helical thin filaments
  • have myosin binding sites
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48
Q

regulatory proteins

A

associate with thick and thin filaments to control contraction

troponin - binds Ca2+, moves tropomyosin to reveal myosin binding sites on thin filament

tropomyosin - blocks myosin binding sites on thin filaments

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49
Q

troponin

A

regulatory protein - binds Ca2+, moves tropomyosin to reveal myosin binding sites on thin filament

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50
Q

tropomyosin

A

regulatory protein - blocks myosin binding sites on thin filaments

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51
Q

structural proteins

A

stabilize / connect sarcomere to other structures

there are dozens, but know 2

titin - large elastic protein, spans M line to Z disc, stabilizes position of thick filaments

dystrophin - connect thin filaments to integral membrane proteins in the sarcolemma, transmits tension of sarcomere to tendons

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52
Q

titin

A

structural protein - spans Z disc to M line, stabilizes thick filaments

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53
Q

dystrophin

A

structural proteins - connects thin filaments to integral membrane proteins in sarcolemma, which attach to ECM components that attach to the fascia transmitting tension to tendons

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54
Q

how does dystrophin transmit tension of sarcomeres to tendons?

A

tension is transmitted from thin filaments to transmembrane proteins (via dystrophin) attached to components of ECM. This is then attached to fascia which form tendons

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55
Q

contraction cycle steps (4)
assume Ca is already binded to troponin

A
  1. myosin binds and hydrolyzes ATP
  2. myosin binds thin filaments, forms cross bridge
  3. myosin pulls thin filaments, power stroke
  4. myosin releases thin filaments
56
Q

contraction cycle step 1 in detail

A

myosin binds and hydrolyzes ATP

myosin head hydrolyzes (makes ATP go to ADP and a P) ATP and becomes energized

57
Q

contraction cycle step 2 in detail

A

myosin binds to thin filaments, forms cross bridge

myosin head will bind to actin, provided the myosin binding site is free (troponin has moved tropomyosin). cross bridge will form between myosin head and myosin binding site on actin

58
Q

contraction cycle step 3 in detail

A

myosin pulls thin filaments, power stroke

myosin head pivots, pulling thin filament past the thick one to the centre of the sarcomere, also called a power stroke (think of rowing an ore)

59
Q

contraction cycle step 4 in detail

A

myosin releases thin filament

a new ATP will bind to the myosin head, which will detach the cross bridge between myosin head and actins myosin binding site

60
Q

role of Ca2+ in muscle contraction

A

change the conformation of troponin, which will let troponin move tropomyosin off of the myosin binding sites on actin

61
Q

what happens to the H zone as the sarcomere shortens

A

it disappears

62
Q

what happens to the I band as the sarcomere shortens

A

it narrows

63
Q

how to sarcomeres move bones?

A

they shorten and pull on adjacent sarcomeres, they keep transmitting tension until the whole muscle fibre shortens

64
Q

4 steps of how sarcomeres move bones

A
  1. sarcomere shortens
  2. pulls connective tissue
  3. pulls on tendons
  4. moves bones
65
Q

length tension relationship

A

there is an optimal amount of filament overlap at rest

if overlap is too much, myosin cannot generate a lot of tension
- no room for sliding of thin filaments
if not enough, myosin cant generate much tension
- too few cross bridges

66
Q

where is Ca2+ for muscle contraction stored

A

SER (sarcoplasmic) and mitochondria

67
Q

NMJ (neuromuscular junction)

A

where neurons and muscles meet, where somatic muscle neuron releases chemical signals (eg, acetylcholine)

68
Q

acetylcholine

A

released by neurotransmitters at NMJ, will bind to ligand gated ion channel and cause slight depolarization

69
Q

ligand gated ion channel

A

acetylcholine will bind to this and there will be slight depolarization in the cell, causing the voltage gated sodium channels to open

70
Q

ratio of sodium potassium pump

A

3:2
3 Na+ out / 2K+ in

71
Q

the inside of the cell is more ______ than the outside

A

negative

72
Q

depolarization

A

when the cell has a less negative charge than resting

73
Q

repolarization

A

the restoration of a negative membrane potential after depolarization

74
Q

what causes changes in membrane potential during action potentials?

A

plasma membrane transporters

  • voltage gated ion channels
  • signal that opens them is a change in membrane potential
  • they facilitate diffusion and let ions flow down their gradients
75
Q

voltage gated sodium channels (VGSCs)

A

allow Na+ to enter the cell
- only open when a change in membrane potential occurs
(in this case by the ligand gated channels)

76
Q

how does acetylcholine binding to a ligand gated ion channel cause depolarization?

A

acetylcholine binds to a ligand gated channel which allows sodium into the cell. this causes a very slight depolarization which opens the Voltage gated sodium channels and will fully depolarize the cell

77
Q

when does repolarization occur?

A

when the voltage gated potassium channels open and the sodium ones close

78
Q

voltage gated potassium channels (VGKCs)

A

responsible for repolarization
- slower to open than VGNCs
- once open K+ flows rapidly out
- close as membrane repolarizes

79
Q

how to action potentials stimulate muscle contraction

A

excitation-contraction coupling

80
Q

excitation contraction coupling

A
  • span of events that release calcium from the Sarcoplasmic reticulum to carry out contraction
  • when action potential is done, Ca2+ ATPases pump it back to the SER or out of the cell and muscles relax
81
Q

steps of excitation contraction coupling (3)

A
  1. action potential travels along sarcolemma
  2. triggers change in VGCCs that causes release of Ca2+ into the sarcoplasm
  3. Ca2+ carries out its processes with troponin and such
82
Q

VGCCs (how much does it increase ca conc)

A
  • has a plug in the sarcolemma, when moved Ca2+ rushed out of the SR into the cell
  • increase intracellular Ca concentration by 10x
83
Q

acetylcholinesterase

A

enzyme that degrades acetylcholine

84
Q

what happens when there is no Ca2+ in the sarcoplasm?

A

muscles are relaxed

85
Q

all 9 steps of muscle contraction
(all steps, excitation contraction coupling as well)

A
  1. nerve action potential in somatic motor neuron triggers release of acetylcholine
  2. ACh binds receptors, triggering muscle action potential
  3. acetycholinesterase destroys ACh to prevent more action potentials unless there is more ACh
  4. MAP travels along sarcolemma, triggers change in VGCCs, releases Ca2+ into sarcoplasm
  5. Ca2+ binds troponin, moving tropomyosin off myosin binding sites on actin
  6. myosin heads bind actin (cross bridge), power stroke, release
  7. VGCCs close, Ca2+ ATPase pumps Ca2+ into SR or out of cell (active transport)
  8. tropomyosin moves back onto actin, blocking myosin binding sites
  9. muscle relaxes
86
Q

action potential to contraction ratio

A

1:1

87
Q

more frequent action potentials =

A

more tension

88
Q

motor unit

A

1 somatic motor neuron + all of the skeletal muscle fibres it synapses with (~150)

89
Q

large muscles have many

A

motor units

90
Q

twitch contraction

A

contraction generates in all skeletal muscle fibres of one motor unit due to one action potential

91
Q

3 phases of twitch contractions

A

latent period
contraction period
relaxation period

92
Q

latent period of twitch contraction

A

2 msecs
delay between stimulus and muscle action
period in which action potential is moving through the sarcolemma and calcium is being released from the SR

93
Q

contraction period of twitch contraction

A

10-100msecs
cross bridges form and sarcomeres shorten
maximum tension develops in this period

94
Q

relaxation period of twitch contraction

A

Calcium pumped back into SR
myosin detaches from actin
tension decreases

95
Q

refractory period

A

a muscle cannot respond to 2 stimuli at once
temporarily unresponsive to new signals

96
Q

muscle tone functions to ____

A

prevent fatigue, make movements smooth rather than jerky

97
Q

what is muscle tone?

A

some skeletal muscles produce tension to stabilize positions, but not enough to move bones (eg, postural muscles in the neck)

98
Q

which motor units work first in contraction of bigger muscles like the biceps brachii?

A

weaker, than stronger

99
Q

muscle tone produces ____

A

small involuntary contractions of alternating motor units that lead to slight stiffness of the muscle

100
Q

2 types of contractions (+ subtypes)

A

isotonic
- concentric
- eccentric

isometric

101
Q

isotonic contractions

A

concentric
eccentric

102
Q

concentric contractions

A

isotonic contraction

occur when the muscle shortens to decrease the angle around a joint
(biceps curls)

103
Q

eccentric contractions

A

isotonic contraction

occurs when muscle resists a load as it lengthens
(the negative of preacher curls)

104
Q

isometric contraction

A

tension generated is not enough to move the load, but functions to stabilize many joints
(static plate hold)

105
Q

what do muscles require ATP for other than contraction?

A

membrane transport, protein synthesis

106
Q

3 ways muscles generate ATP

A
  1. consuming creatine phosphate
  2. aerobic respiration
  3. anaerobic glycolysis
107
Q

consuming creatine phosphate (way to make ATP) (what is the catalyst)

A

unused ATP is dephosphorylated to make creatine phosphate. muscles can rapidly dephosphorylate creatine phosphate to regenerate ATP. both to and from transfers are catalyzed by creatine kinase

108
Q

creatine consumption - analogy

A

storing money in a bank account when not needed, can withdraw quickly at any time

109
Q

creatine kinase

A

catalyst that catalyzes the forward and backward reactions of creatine + phosphate = creatine phosphate to either store (forward) or make (backward) ATP

110
Q

aerobic respiration simple steps (3)

A
  1. glycolysis
  2. products transported to mitochondria
  3. many reactions occur to make lots of ATP
111
Q

aerobic respiration full process

A
  1. glucose broken into 2 pyruvate, generates 2 net ATP and NADH (loaded w/electrons)
  2. pyruvate sent to mitochondria if O2 is present
  3. converts carbons to CO2 - exhaled, electrons from bonds go to electron transport chain
  4. flow of e- down the chain = free energy = harnessed to make 30-32 ATP
112
Q

number of ATP produced per glucose

A

2

113
Q

number of ATP produced per glucose with oxygen

A

30-32

114
Q

anaerobic glycolysis

A

happens when O2 is absent and muscles cant respire products of glycolysis. pyruvate will consume electrons from NADH and become lactic acid. this acts as a place for e- to go since there is no terminal receptor, O2. NADH becomes NAD+, and glycolysis can continue

115
Q

how does pyruvate fermenting to lactic acid facilitate ATP synthesis?

A

pyruvate accepts electrons from NADH and turns it into NAD+, and that will be used to preform glycolysis again

116
Q

aerobic respiration chemical reaction

A

glucose + O2 –> CO2 + H2O + ATP (30-32)

117
Q

glycolysis chemical reaction (no O2)

A

glucose + 2NAD+ –> 2pyruvate + 2NADH + 2ATP

118
Q

mitochondrial reactions in aerobic respiration

A

krebs cycle mainly

119
Q

why do muscles needs O2 after exercise? (3)

A
  • replenish myoglobin
  • convert lactic acid back to glucose in the liver
  • replenish creatine phosphate
120
Q

oxygen debt

A

muscles in need of O2 AFTER exercise

121
Q

3 types of muscle fibres
(not skeletal, cardiac , etc)

A

slow oxidative fibres
fast oxidative-glycolytic fibres
fast glycolytic fibres

122
Q

slow oxidative fibres

A

dark red
- slow contraction (100-200msecs)
- do not fatigue easily - function in postural muscles/endurance
- oxidative - aerobic respiration as main metabolic mode

123
Q

fast oxidative-glycolytic fibres

A

rosey colour - largest
- fast contraction (<100msecs)
- not as resistant to fatigue, reaches max tension fast
- used in moderate exercise
- oxidative - aerobic respiration as main
- glycolytic - can use anaerobic glycolysis
- large glycogen stores

124
Q

fast glycolytic fibres

A

white in colour
- reach max tension quick but fatigue easily
- function during quick intense movements
- large glycogen stores
- uses anaerobic glycolysis when O2 is limited

125
Q

what gives muscle cells their colour? which muscle cells have which colour?

A

myoglobin and capillaries - dark red or rosey
few of those and few mitochondria - white

slow oxidative fibres - dark red
fast oxidative-glycolytic fibres - rosey
fast glycolytic fibres - white

126
Q

cardiac muscle tissue features (there are fucking lots)

A
  • found in heart
  • striated
  • intercalated discs
  • has desmosomes and gap junctions
  • no epimysium
  • single nucleus per fibre
  • have more/larger mitochondria than other muscle cells
  • longer lasting contractions (10-15x) due to calcium proteins closing slowly
  • autorhythmic - no acetylcholine required
  • mainly uses aerobic respiration, anaerobic for short periods
127
Q

smooth muscle tissue

A
  • NOT arranged in sarcomere
  • intermediate filaments assist in contraction
  • not regularly arranged - hence non striated
  • single nucleus
  • no t tubules
  • caveolae - collect Ca2+ rich interstitial fluid
128
Q

caveolae

A

shallow invaginations of the sarcolemma in smooth muscle cells that collect calcium rich interstitial fluid

129
Q

how does smooth muscle contract?

A

thin filaments are attached to dense bodies, so when they contract, the cell shortens and twists

130
Q

why does smooth muscle contract slower than any other type?

A

they have a smaller SR and no T tubules = delay in calcium reaching troponin

131
Q

what contributes to smooth muscle tone?

A

calcium leaves smooth muscle slowly

132
Q

types of smooth muscle tissue (2)

A

viceral
multi unit

133
Q

viceral smooth muscle

A
  • autorhythmic
  • gap junstions
  • found in walls of hollow organs and blood vessels
  • single unit
134
Q

multi unit smooth muscle

A
  • each fibre has its own autonomic motor neuron
  • found in walls of large arteries, arrector pili, around pupil of eye
135
Q

unique smooth muscel stress-relaxation response and why its important

A

when stretched, smooth muscle initially contracts, and tension decreases over time

important in hollow organs and vessels so contents remain under constant pressure

136
Q

Ca 2+ ATPases

A

pump Ca2+ back into the SR or out of the cell once it is no longer needed for muscle contraction

Biol 1190 (31 decks)

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