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ESA1 > ToB 14 Muscle > Flashcards

ToB 14 Muscle Flashcards

1
Q

Define myalgia:

A

Muscle pain

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2
Q

Define myasthenia:

A

Muscle weakness

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3
Q

Define myopathy:

A

A disease of muscle tissue

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4
Q

Define myoclonus:

A

Sudden spasm of groups of muscles

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5
Q

Define sarcolemma:

A

Outer membrane of a muscle cell

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6
Q

Define sarcoplasm:

A

Cytoplasm of a muscle cell

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7
Q

Define sarcoplasmic reticulum:

A

Smooth endoplasmic reticulum of a muscle cell

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8
Q

What are the 3 types of muscle?

A

1) Cardiac
2) Skeletal
3) Smooth

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9
Q

Define striated:

A

Striped appearance

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10
Q

Which muscle type(s) appear striated?

A

Cardiac

Skeletal

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11
Q

Which muscle type(s) appear non-striated?

A

Smooth

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12
Q

Which is the largest muscle cell type?

A

Skeletal muscle cells

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13
Q

What muscle cell type is approx. 50-100 um long, and 10-20 um in diameter?

A

Cardiac

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14
Q

What muscle cell type is approx. 20-200 um long, and 5-10 um in diameter?

A

Smooth

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15
Q

What muscle cell type is approx. 1mm-20cm long, and 10-100 um in diameter?

A

Skeletal

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16
Q

Which muscle cell type has the largest diameter?

A

Skeletal

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17
Q

Which muscle cell type is branched?

A

Cardiac

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18
Q

How does being branched suit the function of cardiac muscle cells?

A

It allows every cell to be in contact with 4/5 other cells, allowing the rapid conduction of electrical impulse across, for rapid and precise muscle contraction.

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19
Q

Which muscle cell type has peripherally placed nuclei?

A

Skeletal

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20
Q

Which muscle cell type is multinucleated?

A

Skeletal

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21
Q

Which muscle cell type(s) are cylindrical?

A

Skeletal

Cardiac

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22
Q

Describe the shape of a smooth muscle cell:

A

Spindle-shaped
Tapering ends
Fusiform

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23
Q

Which muscle type(s) have a single central nucleus?

A

Cardiac

Smooth

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24
Q

In what type of muscle do the cells run the whole length of the muscle?

A

Skeletal

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25
Q

What is the difference between the somatic nervous system and the autonomic nervous system?

A

The somatic system controls things which are under conscious control, the autonomic system controls things which are not under voluntary control.

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26
Q

Which muscle type is under somatic control?

A

Skeletal muscle

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27
Q

Which muscle type(s) are under autonomic control?

A

Smooth

Cardiac

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28
Q

Which muscle type generates slow/sustained or rhythmic contractions?

A

Smooth

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29
Q

Which muscle type gives rapid, forceful contractions?

A

Skeletal

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30
Q

From which embryonic germ layer does muscle derive?

A

Mesoderm

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31
Q

What is the name of the cell which can differentiate into a muscle cell?

A

Myoblast

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32
Q

How do skeletal muscle cells form?

A

Myoblasts line up forming a chain or primary myotubule. These develop gap junctions, and the central nuclei are peripherally displaced due to the production of actin and myosin.

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33
Q

What are the 3 types of skeletal muscle fibres?

A

1) Red (slow contracting)
2) Intermediate
3) White (fast fatigue)

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34
Q

With which stain can you see the different types of skeletal muscle fibres present?

A

No stain required to differentiate between the different skeletal muscle fibres.

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35
Q

Which skeletal muscle fibre type has the largest diameter?

A

White (fast fatigue) fibres

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36
Q

Which skeletal muscle fibre type has the smallest diameter?

A

Red (slow contracting) fibres

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37
Q

Which skeletal muscle fibre type has the richest vascularisation?

A

Red (slow contracting) fibres

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38
Q

Compare the amount of mitochondria present in the different skeletal muscle fibre types:

A

Red fibres have the most mitochondria present. Intermediate fibres have less, with white fibres having the least mitochondria present.

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39
Q

Which skeletal muscle fiber type fatigues the fastest?

A

White fibres

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40
Q

Why do oxidative slow contracting skeletal muscle fibers appear red?

A

Because of the high proportion of myoglobin (red) in oxidative muscle fibres, compared to the white, fast fatigue fibers.

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41
Q

Which skeletal muscle fiber type is richest in oxidative enzymes?

A

Red (slow contracting)

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42
Q

Which skeletal muscle fiber type has the least amount of oxidative enzymes present?

A

White (fast fatigue)

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43
Q

Which skeletal muscle fiber type has the most myosin ATPase activity?

A

White (fast fatigue)

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44
Q

Why do white skeletal muscle fibers require higher myosin ATPase activity than red fibres?

A

White fibers give faster, stronger contractions. The strength and speed of a contraction depends on the speed that cross-bridge cycling can occur. More ATPase activity means the cycling can occur faster.

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45
Q

Which type of skeletal muscle fiber contains the most myoglobin?

A

Red oxidative fibers

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46
Q

Why do red fibers contain more myoglobin than white skeletal muscle fibers?

A

Red fibers are oxidative, so requires myoglobin, which is an oxygen-binding protein, which provides a store of oxygen within the fiber.

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47
Q

Name the oxygen binding protein found in high quantities in oxidative skeletal muscle fibers:

A

Myoglobin

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48
Q

Fast glycolytic skeletal muscle fibers have a fast contraction velocity due to high activity of ?

A

Myosin ATPase

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49
Q

Fast glycolytic skeletal muscle fibers produce more tension in a twitch because they have more ?

A

Cross-bridges present

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50
Q

What type of skeletal muscle fiber is innervated by the smallest somatic efferent neurons?

A

Slow, oxidative (red)

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51
Q

Which size neurons are the easiest to excite?

A

The smallest

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52
Q

Which skeletal muscle fibre type is recruited first when causing a muscle contraction?

A

Slow, oxidative (red)

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53
Q

Slow oxidative fibers are resistant to ?

A

Fatigue

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54
Q

Through recruitment, an increase in muscle force is achieved by increased activation of ?

A

Motor units

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55
Q

Which type of skeletal muscle fiber has the most neuromuscular junctions present?

A

White (fast fatigue)

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56
Q

What is the function of the extraocular muscles?

A

Control the movement of the eye

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57
Q

What type of skeletal muscle fibers are found in the postural muscles of the back?

A

Red oxidative fibers

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58
Q

What type of skeletal muscles fiber are the extraocular fibers?

A

White fast fatigue fibers

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59
Q

How would the skeletal muscle fibers differ in the breast muscles of migrating birds vs domestic hen?

A

Migrating birds = red oxidative fibers

Domestic hen = white fast fatigue fibers

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60
Q

What is a fascicle?

A

Group of muscle fibers/cells, wrapped by perimysium

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61
Q

What membrane covers each muscle fiber/cell individually?

A

Endomysium

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62
Q

What membrane encases a fascicle?

A

Perimysium

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63
Q

What is the epimysium?

A

The membrane/sheath which encases the entire muscle (groups of muscle facicles)

64
Q

What connects muscle to bone?

A

Tendons

65
Q

Are all skeletal muscles attached to bone?

A

No, but most are

66
Q

How is the tongue so mobile?

A

The extrinsic muscles of the tongue have multidirectional orientation, and interdigitate with connective tissue which has high plasticity and strength.

67
Q

What is carried to and from the muscle via the perimysium?

A

Nerves
Blood vessels
Lymphatic vessels

68
Q

What letter is used to name the dark band of a striated muscle filament?

A

A (anisotropic) band

69
Q

What letter is used to name the light band of a striated muscle filament?

A

I (isotropic) band

70
Q

Name the dark band of a striated muscle filament, and what it contains:

A

A(nisotropic) band, containing myosin and interdigitating actin fibers

71
Q

Name the light band of a striated muscle filament, and what it contains:

A

I(sotropic) band, containing only actin

72
Q

What is a sarcomere?

A

A contractile unit of a myofibril in striated muscle, consisting of a dark band and the nearer half of each adjacent pale band (between 2 adjacent z lines)

73
Q

What is the H zone of a striated myofibril?

A

The area which contains only myosin. It is a lighter band present in the center of the A band.

74
Q

What disc lies in between sarcomeres?

A

Z disc

75
Q

Name the dark line in the middle of the A band:

A

M line

76
Q

Where are the actin filaments anchored, within a striated myofibril?

A

Z line

77
Q

What does MHAZI mean?

A 
M line lies within the
H band, which is within the
A band, which lies between the 
Z lines, which are present in the
I band
78
Q

What happens to the length of the A, H and I bands of striated muscle with contraction?

A

A band stays the same, H and I band shortens as the actin interdigitates with the myosin

79
Q

What types of filaments are present in a cross section of a myofilament, cut through the H band?

A

Myosin filaments only

80
Q

What types of filaments are present in a cross section of a myofilament, cut through the A band during contraction of the muscle?

A

Actin and myosin filaments, interdigitating

81
Q

How does the presence of different filaments in the A band change with contracted vs stretched muscle?

A

During contraction both actin and myosin filaments are present, as the muscle shortens so the filaments overlap.
When the muscle is stretched, z lines move apart, and there is less/no overlap of actin and myosin, so only myosin will be present in the A band.

82
Q

What 3 molecules make up the troponin complex?

A

TnI
TnC
TnT

83
Q

What molecules complex to form the thin filaments in striated muscle?

A

Actin
Troponin
Tropomyosin

84
Q

Which Troponin forms are most useful assays as a clinical marker for cardiac ischemia?

A

TnI

TnT

85
Q

What is the assay of choice, used as a marker for cardiac ischemia?

A

Troponin assay

86
Q

Within what time frame must troponin levels be measured to give useful marker for cardiac ischemia?

A

20 hrs

87
Q

Within what time frame is troponin released from ischaemic cardiac muscle?

A

1 hr

88
Q

Why is a troponin assay so reliable as a marker for cardiac ischemia?

A
  • Serum troponin is very constant, so the smallest changes are indicative of cardiac ischaemia
  • Ischaemic cardiac muscle will always release troponin
  • Relatively long half life (stays in blood for ~20hrs)
89
Q

An extremely high level of troponin in the blood is indicative of what?

A

Cardiac ischaemia.

Cannot be used to estimate degree of damage, as not proportional.

90
Q

List the structural features of a myosin II molecule:

A
  • 2 globular heads of heavy chain
  • Neck/hinge region of heavy chain
  • Tail-like structure of heavy chains coiled (alpha helix)
91
Q

Which form of myosin molecules generate force in skeletal muscle contractions?

A

Myosin II molecules

92
Q

Which component of the thin filament forms a bistranded helix?

A

Actin filaments

93
Q

Why can’t cross-bridging occur in the center of a sarcomere?

A

There are no myosin heads protruding from the thick filaments in the center of the sarcomere.

94
Q

Which type of filament contains ATPase activity?

A

Thick filament (myosin)

95
Q

How many myosin binding sites does each actin molecule have?

A

1

96
Q

Where does Ca2+ bind to initiate muscle contraction?

A

TnC of troponin complex

97
Q

How does the presence of Ca2+ allow cross-bridging to occur?

A
  • Ca2+ binds to TnC
  • Conformational change
  • Troponin complex is bound to Tropomyosin, and the conformation change causes Tropomyosin to move away from the myosin binding sites on actin
98
Q

Which part of the thin filament blocks the myosin binding sites on actin?

A

Tropomyosin

99
Q

The presence of which ion is required for muscle contraction?

A

Ca2+

100
Q

Name the 5 states during the cross-bridge cycle:

A

1) Attached state
2) Released state
3) Cocked state
4) Cross-bridge state
5) Power-stroke state

101
Q

What causes the cross-bridge cycle to move from the attached state to the released state?

A

ATP binding to the myosin head = breaks cross-bridge

102
Q

What causes the cross-bridge cycle to move from the released state to the cocked state?

A

ATP hydrolysis (myosin head has ATPase activity)

103
Q

What causes the cross-bridge cycle to move from the cocked state to the cross-bridge state?

A

High affinity of myosin for actin at binding site

104
Q

What causes the cross-bridge cycle to move from the cross-bridge state to the power-stroke state?

A

Power-stroke requires the conformational change of the myosin head rotation, caused by the release of phosphate

105
Q

What causes the cross-bridge cycle to move from the power-stroke state to the attached state?

A

Release of ADP

106
Q

Why does rigor mortis occur?

A

Once body has died, ATP will not be synthesised anymore. Muscle requires ATP to break the cross-bridge and enter the relaxed state, so after death muscle will be contracted.

107
Q

What breaks the cross-bridge between actin and myosin during muscle contraction?

A

ATP binding to myosin head

108
Q

Approximately how far does the myosin head advance between the released state and the cocked state?

A

5 nm

109
Q

The triad of sarcoplasmic reticulum and t-tubule within skeletal muscle runs over what structural point of the myofilaments?

A

Where the A and I band join

110
Q

What neurotransmitter is contained within the vesicles of motor neurones innervating skeletal muscle?

A

Acetylcholine

111
Q

Define neuromuscular junction:

A

The synapse between a motor neurone and a skeletal muscle.

112
Q

Which neurotransmitter is present in a neuromuscular junction?

A

Acetylcholine

113
Q

What causes the initial depolarisation of the sarcolemma?

A

Uptake of Acetylcholine from neuromuscular junction,

causes voltage-gated Na+ channels to open, so Na+ movement into cell causes depolarisation of sarcolemma

114
Q

Define t-tubule:

A

Invaginations of the sarcolemma running deep through the skeletal muscle, allowing contraction to be initiated quickly throughout the whole myofibril.

115
Q

Why can muscle not contract at low intracellular [Ca2+]?

A

The troponin and tropomyosin complex blocks the myosin binding site on actin during low [Ca2+].

116
Q

Which 2 structures are key to the regulation of intracellular [Ca2+]?

A

1) T-tubules

2) Sarcoplasmic reticulum

117
Q

Why do muscle cells have a sarcoplasmic reticulum?

A

It is a store of Ca2+, which can be released very close to the myofibrils

118
Q

What type of fluid are t-tubules filled with?

A

Extracellular fluid, as they are invaginations of the sarcolemma

119
Q

Why do t-tubules project deep into a skeletal muscle cell?

A

They allow the action potential to be propagated throughout the muscle cell, causing regular contractions

120
Q

What causes the opening of gated Ca2+ channels in the SR of skeletal muscle?

A

The AP generated at the neuromuscular junction is propagated down t-tubules, causing voltage-sensor proteins in the t-tubule to undergo conformational change. These proteins are linked to the gated-Ca2+ channels of the SR, and cause them to open (after conformational change).

121
Q

A triad of sarcoplasmic reticulum and t-tubules is present in what type of muscle?

A

Skeletal muscle

122
Q

A diad of sarcoplasmic reticulum and t-tubules is present in what type of muscle?

A

Cardiac muscle

123
Q

The t-tubules of cardiac muscle lie in register with what part of a myofilament?

A

Z/intercalated discs

124
Q

What type of intercellular junctions are present in the cardiac intercalated discs?

A

Gap junctions

Desmosomes

125
Q

Define gap junction:

A

Junctions between cells which allow the transfer of small molecules/ions, and electrical coupling. They directly connect the cytoplasm of the 2 cells.

126
Q

Define desmosome:

A

Adhesion sites which provide strong intercellular adhesion, by anchoring the intermediate filaments of the cells together.

127
Q

What junctions are required between cardiac myocytes to allow electrical coupling?

A

Gap junctions

128
Q

What junctions are required between cardiac myocytes to anchor them together?

A

Desmosomes or adherens junctions

129
Q

Where are cardiac action potentials generated from?

A

Sinoatrial (SA) node

130
Q

What is the name of the fibres which carry the cardiac AP from the atrioventricular node to the ventricles?

A

Purkinje fibres

131
Q

What is the name of the lining of the interior of the heart?

A

Endocardium

132
Q

How are purkinje fibre cells adapted for rapid electrical conduction?

A
  • Large cells
  • Many gap junctions
  • Contain abundant glycogen
133
Q

Do purkinje fibre cells contain more or less myofilaments compared to cardiac myocytes?

A

Much less

134
Q

Compare the speed of conduction between purkinje fiber cells, and cardiac muscle fibres:

A

Purkinje fiber cells conduct electrical impulses MUCH FASTER ~ 3-4m/s compared to 0.5m/s in cardiac muscle fibers

135
Q

Where are the t-tubules located in smooth muscle cells?

A

Smooth muscle doesn’t have t-tubules

136
Q

Compare the stimuli required for contraction between skeletal and smooth muscle:

A

Skeletal muscle requires Acetylcholine binding at post-synaptic membrane of sarcolemma
Smooth muscle responds to: nerves/hormones/drugs etc.

137
Q

Describe the shape and function of myoepithelial cells:

A

Stellate smooth muscle cells which form a basketwork around the secretory units of some exocrine glands, to aid secretion.

138
Q

Name the 2 types of modified smooth muscle cells which can occur singly:

A

1) Myoepithelial cells

2) Myofibroblasts

139
Q

Where are myofibroblasts found?

A

At sites of wound healing

140
Q

What type of modified smooth muscle cells are found at sites of wound healing?

A

Myofibroblasts

141
Q

What type of muscle cell is a myofibroblast?

A

Modified smooth muscle cell

142
Q

What type of muscle cell is a myoepithelial cell?

A

Modified smooth muscle cell

143
Q

What is the function of myofibroblasts?

A

Produce collagenous matrix and to contract, to aid wound healing

144
Q

What type of muscle is present in the wall of the small intestine?

A

Smooth muscle

145
Q

From what structure are neurotransmitters released to innervate smooth muscle?

A

Varicosities of nerve fibers

146
Q

Why do smooth muscle cells contract in a twisting way?

A

The intermediate filaments (of actin and myosin) are organised diagonally so that they spiral down the smooth muscle cell. When these contract, the cell shortens and spirals.

147
Q

What anchor the intermediate filaments to the sarcolemma?

A

Dense bodies

148
Q

What are caveoli, and where are they found?

A

Small invaginations of the sarcolemma, increasing the surface area of smooth muscle cells

149
Q

What are muscle satellite cells?

A

Cells which can differentiate into skeletal muscle cells, important for growth and repair of the muscle cells.

150
Q

How can skeletal muscle repair itself after injury?

A

Stimulate activation and proliferation of satellite cells, which can either fuse and repair the damaged myofiber, or create a new myofiber.

151
Q

How can cardiac muscle repair itself after injury?

A

Cardiac muscle cannot repair after injury, instead fibroblasts lay down scar tissue.

152
Q

What type of muscle is incapable of repair/regeneration?

A

Cardiac muscle

153
Q

What type of muscle cell can undergo mitosis?

A

Smooth muscle cells

154
Q

What happens to cardiac muscle after injury?

A

Fibroblasts lay down scar tissue

155
Q

What happens to smooth muscle after injury?

A

Smooth muscle cells can divide via mitosis, so can replace damaged cells.

ESA1 (22 decks)

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