ToB 14 Muscle Flashcards Preview

ESA1 > ToB 14 Muscle > Flashcards

Flashcards in ToB 14 Muscle Deck (155)
1

Define myalgia:

Muscle pain

2

Define myasthenia:

Muscle weakness

3

Define myopathy:

A disease of muscle tissue

4

Define myoclonus:

Sudden spasm of groups of muscles

5

Define sarcolemma:

Outer membrane of a muscle cell

6

Define sarcoplasm:

Cytoplasm of a muscle cell

7

Define sarcoplasmic reticulum:

Smooth endoplasmic reticulum of a muscle cell

8

What are the 3 types of muscle?

1) Cardiac
2) Skeletal
3) Smooth

9

Define striated:

Striped appearance

10

Which muscle type(s) appear striated?

Cardiac
Skeletal

11

Which muscle type(s) appear non-striated?

Smooth

12

Which is the largest muscle cell type?

Skeletal muscle cells

13

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

Cardiac

14

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

Smooth

15

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

Skeletal

16

Which muscle cell type has the largest diameter?

Skeletal

17

Which muscle cell type is branched?

Cardiac

18

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

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.

19

Which muscle cell type has peripherally placed nuclei?

Skeletal

20

Which muscle cell type is multinucleated?

Skeletal

21

Which muscle cell type(s) are cylindrical?

Skeletal
Cardiac

22

Describe the shape of a smooth muscle cell:

Spindle-shaped
Tapering ends
Fusiform

23

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

Cardiac
Smooth

24

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

Skeletal

25

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

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

26

Which muscle type is under somatic control?

Skeletal muscle

27

Which muscle type(s) are under autonomic control?

Smooth
Cardiac

28

Which muscle type generates slow/sustained or rhythmic contractions?

Smooth

29

Which muscle type gives rapid, forceful contractions?

Skeletal

30

From which embryonic germ layer does muscle derive?

Mesoderm

31

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

Myoblast

32

How do skeletal muscle cells form?

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.

33

What are the 3 types of skeletal muscle fibres?

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

34

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

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

35

Which skeletal muscle fibre type has the largest diameter?

White (fast fatigue) fibres

36

Which skeletal muscle fibre type has the smallest diameter?

Red (slow contracting) fibres

37

Which skeletal muscle fibre type has the richest vascularisation?

Red (slow contracting) fibres

38

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

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

39

Which skeletal muscle fiber type fatigues the fastest?

White fibres

40

Why do oxidative slow contracting skeletal muscle fibers appear red?

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

41

Which skeletal muscle fiber type is richest in oxidative enzymes?

Red (slow contracting)

42

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

White (fast fatigue)

43

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

White (fast fatigue)

44

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

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.

45

Which type of skeletal muscle fiber contains the most myoglobin?

Red oxidative fibers

46

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

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

47

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

Myoglobin

48

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

Myosin ATPase

49

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

Cross-bridges present

50

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

Slow, oxidative (red)

51

Which size neurons are the easiest to excite?

The smallest

52

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

Slow, oxidative (red)

53

Slow oxidative fibers are resistant to ?

Fatigue

54

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

Motor units

55

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

White (fast fatigue)

56

What is the function of the extraocular muscles?

Control the movement of the eye

57

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

Red oxidative fibers

58

What type of skeletal muscles fiber are the extraocular fibers?

White fast fatigue fibers

59

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

Migrating birds = red oxidative fibers
Domestic hen = white fast fatigue fibers

60

What is a fascicle?

Group of muscle fibers/cells, wrapped by perimysium

61

What membrane covers each muscle fiber/cell individually?

Endomysium

62

What membrane encases a fascicle?

Perimysium

63

What is the epimysium?

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

64

What connects muscle to bone?

Tendons

65

Are all skeletal muscles attached to bone?

No, but most are

66

How is the tongue so mobile?

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

67

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

Nerves
Blood vessels
Lymphatic vessels

68

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

A (anisotropic) band

69

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

I (isotropic) band

70

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

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

71

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

I(sotropic) band, containing only actin

72

What is a sarcomere?

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

What is the H zone of a striated myofibril?

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

74

What disc lies in between sarcomeres?

Z disc

75

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

M line

76

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

Z line

77

What does MHAZI mean?

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

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

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

79

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

Myosin filaments only

80

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

Actin and myosin filaments, interdigitating

81

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

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

What 3 molecules make up the troponin complex?

TnI
TnC
TnT

83

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

Actin
Troponin
Tropomyosin

84

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

TnI
TnT

85

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

Troponin assay

86

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

20 hrs

87

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

1 hr

88

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

- 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

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

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

90

List the structural features of a myosin II molecule:

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

91

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

Myosin II molecules

92

Which component of the thin filament forms a bistranded helix?

Actin filaments

93

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

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

94

Which type of filament contains ATPase activity?

Thick filament (myosin)

95

How many myosin binding sites does each actin molecule have?

1

96

Where does Ca2+ bind to initiate muscle contraction?

TnC of troponin complex

97

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

- 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

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

Tropomyosin

99

The presence of which ion is required for muscle contraction?

Ca2+

100

Name the 5 states during the cross-bridge cycle:

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

101

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

ATP binding to the myosin head = breaks cross-bridge

102

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

ATP hydrolysis (myosin head has ATPase activity)

103

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

High affinity of myosin for actin at binding site

104

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

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

105

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

Release of ADP

106

Why does rigor mortis occur?

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

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

ATP binding to myosin head

108

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

5 nm

109

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

Where the A and I band join

110

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

Acetylcholine

111

Define neuromuscular junction:

The synapse between a motor neurone and a skeletal muscle.

112

Which neurotransmitter is present in a neuromuscular junction?

Acetylcholine

113

What causes the initial depolarisation of the sarcolemma?

Uptake of Acetylcholine from neuromuscular junction,
causes voltage-gated Na+ channels to open, so Na+ movement into cell causes depolarisation of sarcolemma

114

Define t-tubule:

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

115

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

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

116

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

1) T-tubules
2) Sarcoplasmic reticulum

117

Why do muscle cells have a sarcoplasmic reticulum?

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

118

What type of fluid are t-tubules filled with?

Extracellular fluid, as they are invaginations of the sarcolemma

119

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

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

120

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

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

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

Skeletal muscle

122

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

Cardiac muscle

123

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

Z/intercalated discs

124

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

Gap junctions
Desmosomes

125

Define gap junction:

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

126

Define desmosome:

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

127

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

Gap junctions

128

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

Desmosomes or adherens junctions

129

Where are cardiac action potentials generated from?

Sinoatrial (SA) node

130

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

Purkinje fibres

131

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

Endocardium

132

How are purkinje fibre cells adapted for rapid electrical conduction?

- Large cells
- Many gap junctions
- Contain abundant glycogen

133

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

Much less

134

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

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

135

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

Smooth muscle doesn't have t-tubules

136

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

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

137

Describe the shape and function of myoepithelial cells:

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

138

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

1) Myoepithelial cells
2) Myofibroblasts

139

Where are myofibroblasts found?

At sites of wound healing

140

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

Myofibroblasts

141

What type of muscle cell is a myofibroblast?

Modified smooth muscle cell

142

What type of muscle cell is a myoepithelial cell?

Modified smooth muscle cell

143

What is the function of myofibroblasts?

Produce collagenous matrix and to contract, to aid wound healing

144

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

Smooth muscle

145

From what structure are neurotransmitters released to innervate smooth muscle?

Varicosities of nerve fibers

146

Why do smooth muscle cells contract in a twisting way?

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

What anchor the intermediate filaments to the sarcolemma?

Dense bodies

148

What are caveoli, and where are they found?

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

149

What are muscle satellite cells?

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

150

How can skeletal muscle repair itself after injury?

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

151

How can cardiac muscle repair itself after injury?

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

152

What type of muscle is incapable of repair/regeneration?

Cardiac muscle

153

What type of muscle cell can undergo mitosis?

Smooth muscle cells

154

What happens to cardiac muscle after injury?

Fibroblasts lay down scar tissue

155

What happens to smooth muscle after injury?

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