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Z OLD Tissues of the Body > Muscle > Flashcards

Flashcards in Muscle Deck (165):
1

What is myalgia?

Muscle pain

2

What is myasthenia?

Muscle weakness

3

What is myopathy?

Any disease of the muscle

4

What is the sarcolemma?

The outer membrane of muscle cells

5

What is the sarcoplasm?

The cytoplasm of a muscle cell

6

What are the 3 major muscle types?

#NAME?

7

Is skeletal muscle striated?

Yes

8

How big are skeletal muscle fibres?

- 1mm-20cm long
- 10-100µm in diameter

9

What shape are skeletal muscle fibres?

Long parallel cylinders

10

Describe the nuclei of skeletal muscle cells

Multiple peripheral nuclei

11

How are skeletal muscles connected?

Fascicle bundles and tendons

12

What controls skeletal muscle?

Motor neurones

13

Are skeletal muscles under voluntary or involuntary control?

Voluntary

14

Describe the action of skeletal muscles?

Rapid and forceful

15

Is cardiac muscle striated?

Yes

16

How big are cardiac muscle fibres?

- 50-100µm long
- 10-20µm in diameter

17

Describe the shape of cardiac muscle?

Short, branched cylinders

18

Describe the nuclei of cardiac muscle fibres?

Single, central nucleus

19

How is cardiac muscle contraction controlled?

Intrinsic rhythm, under autonomic modulation

20

Is cardiac muscle contraction voluntary or involuntary?

Involuntary

21

Describe the nature of cardiac muscle rhythm?

Lifelong, variable

22

Is smooth muscle striated?

No

23

How big are smooth muscle fibres?

- 20-200µm long
- 5-10µm in diameter

24

What shape are smooth muscle fibres?

Spindle shaped, tapering ends

25

Describe the nuclei of smooth muscle cells?

Single central nucleus

26

How is smooth muscle joined?

By connective tissue, gap and desmosome-type junctions

27

How is smooth muscle controlled?

Autonomic, intrinsic activity, caused by local stimuli

28

Is smooth muscle contraction voluntary or involuntary?

Involuntary

29

Describe the nature of smooth muscle contraction

Slow, sustained or rhythmic

30

How is skeletal muscle developed?

#NAME?

31

What does the myotube have?

A chain of multiple central nuclei

32

What happens to the chain of nuclei in myotubes?

They are gradually displaced to the cell periphery by newly synthesised actin and myosin filaments

33

What happens to myoblasts producing cardiac and smooth muscle?

They do not fuse, but develop gap junctions at a very early stage

34

How do skeletal muscle fibres differ from each other?

In their diameter and their natural colour in vivo

35

What stains corroborate the natural colour of skeletal muscle fibres?

Strain showing reaction to NADH in mitochondria

36

What are the 3 types of skeletal muscle fibre?

#NAME?

37

Which muscles are red, white and intermediate skeletal fibres present in?

All

38

What does the red:white:intermediate proportion depend on?

The functional role of the muscle

39

Comparatively, what is the diameter of red skeletal muscle fibres?

Smaller

40

What are red skeletal muscle fibres rich in?

- Myoglobin
- Vascularisation 
- Mitochondria 
- Oxidative enzymes

41

Of what do red skeletal muscle fibres have few?

#NAME?

42

What kind of contraction does red skeletal muscle fibres induce?

Slow, repetitive, weaker

43

How quickly does red skeletal muscle fatigue?

Slowly

44

Where are red skeletal muscle fibres found?

- Limb muscles of animals 
- Postural muscles of back
- Breast muscle of migrating birds

45

Comparatively, how big are white skeletal muscle fibres?

Larger

46

What do white skeletal muscle fibres have lots of?

#NAME?

47

Of what do white skeletal muscle fibres have few?

- Myoglobin
- Vascularisation 
- Oxidative enzymes

48

What kind of contraction do white skeletal muscle fibres induce?

Faster, stronger

49

Where are white skeletal muscle fibres typically found?

- Extra-ocular muscles 
- Muscles controlling fingers

50

What links muscle to bone?

Tendons

51

What is the epimysium?

Protective sheath over muscle

52

Where does the perimysium exist?

Between bundles of muscle fibres

53

Where are the blood vessels found with respect to the perimysium?

Outside of it

54

What are fasicles?

Bundles of muscle fibres wrapped by perimysium

55

Where is endomysium found?

Between muscle fibres

56

What are possible arrangements for muscle fibres?

- Convergent
- Circular
- Parallel
- Fusiform
- Unipennate
- Bipennate 
- Multipennate

57

Where do skeletal muscle fibres interdigitate?

At myotendinous junctions

58

How do skeletal muscle fibres interdigitate?

With tendon collagen bundles

59

Where does the sarcolemma lie?

Between the collagen bundles and muscle fibres myofilaments

60

What do the extrinsic muscles of the tongue do?

Protrude to tongue, retract it and move it from side to side

61

Where does the extrinsic muscles of the tongue have insertions?

In bone/cartilage

62

Are the intrinsic muscles of the tongue attached to bone?

No

63

What is the result of the intrinsic muscles of the tongue not being attached to bone?

It allows the tongue to change shape, but not position

64

How to the skeletal muscles of the tongue often terminate?

With interdigitation with the collagen and extracellular matrix of surrounding connective tissues

65

What accounts for the mobility of the tongue?

The plascity and strength of connective tissues, and multidirectional orientation of the muscle fibres

66

What is a striated muscle cell called?

A muscle fibre

67

What is the plasmalemma of a muscle cell sometimes called?

It’s sarcolemma

68

What is the sarcomere?

The unit of striated muscle- the distance between two Z lines

69

Which band appears dark?

A

70

Which band appears light?

I

71

What happens to the sarcomeres in the sliding filament mechanism?

They get shorter-
- I band and H zone shorten
- A band remains the same

72

What are skeletal muscles composed of?

Fasicles

73

What are fasicles composed of?

Muscle fibres (cells)

74

What are muscle fibres composed of?

Myofibrils

75

What are the myofibrils?

#NAME?

76

What forms the thin filaments of skeletal and cardiac muscle?

A complex of actin, tropomyosin and troponin

77

How can troponin assays be used as a diagnostic tool?

Can be used as a marker for cardiac ischaemia

78

What types of troponin especially are used as a marker for cardiac ischaemia?

I and T forms

79

How can troponin assays be used a marker for cardiac ischaemia?

It’s released from ischaemic cardiac muscle within an hour, so the smallest changes in troponin levels are indicative or cardiac muscle damage

80

Is the quantity of troponin found proportional to degree of muscle damage?

Not necessarily

81

Describe the structure of an individual myosin molecule

Has a rod-like structure from which two ‘heads’ protrude

82

What does each thick filament consist of?

Many myosin molecules

83

How do the heads of the myosin in the thick filament protrude?

At opposite ends of the filament

84

What do actin filaments form?

A helix

85

What happens to the actin helix?

Tropomyosin molecules coil around it

86

What is the effect of the tropomyosin molecules coiling around the actin helix?

It reinforces it

87

What is attached to each tropomyosin molecule?

A troponin complex

88

What is true of the thick filaments in the centre of the sarcomere?

Thet are devoid of myosin heads

89

What happens to the myosin head in areas of potential overlap?

They extend towards the actin filaments

90

What is the role of ionic calcium in the contraction metabolism?

- When increased amount of ionic calcium bind to TnC of troponin, a conformational change moves tropomyosin way from actin’s binding sites 
- This displacement allows myosin heads to bind to actin, and contraction begins

91

What conformational change is made on binding of calcium?

The troponin has moved down, taking tropomyosin with it

92

What is the result of the action of calcium in muscle contraction?

Muscle contraction only occurs in the presence of calcium ions

93

What is the sliding filament theory of muscle contraction?

- Myosin cross bridge attaches to the actin myofilament 
- ADP+Pi released, producing the working stroke- the myosin head pivots and bends as it pulls on the actin filament, sliding towards the M line 
- New ATP attaches to the myosin head, and the cross bridges detaches 
- As ATP is hydrolysed into ADP+Pi, cocking of the myosin head occurs

94

What state is myosin in at the point of forming cross bridges?

High energy conformation

95

What is meant by the high energy conformation of myosin?

It has ADP+Pi attached

96

When is myosin in the low energy conformation?

When it has ATP attached to the head

97

What is the purpose of the cocking of the myosin head?

Means myosin is ready to bind to a new actin filament

98

What causes movement of skeletal muscle?

Individual myosin heads attaching and flexing at different times

99

What is the rigor configuration?

When the myosin head is bound tightly to actin molecule

100

What causes rigor mortis?

In death, lack of ATP perpetuates the rigor configuration

101

What is at the end of the axons?

Small terminal swellings

102

What do the small terminal swellings of the axon contain?

Acetylcholine

103

What causes the release of acetylcholine?

A nerve impulse

104

What happens to released acetylcholine?

It binds to receptors on the sarcolemma

105

What is the result of acetylcholine binding to receptors?

Initiates an action potential propagated along the muscle

106

Where do nerves come from?

The motor neurone cell body of the spinal cord

107

What is each nerve coming from the spinal cord known as?

A motor neurone

108

What happens to the motor neurone axon?

It branches, and joins to muscle fibres

109

What initiates the contraction of skeletal muscle?

A nerve impulse along the motor neurone arriving at the neuromuscular junction

110

What does the nerve impulse arriving at the neuromuscular junction prompt?

The release of acetylcholine (ACh) into the synaptic cleft

111

What does the release of ACh cause?

Local depolarisation of the sarcolemma

112

What happens as a result of the depolarisation of the sarcolemma?

Voltage-gated Na + channels open, and so it enters the cell

113

What does the influx of Na + to the sarcolemma cause?

General depolarisation, that spreads into the sarcolemma and into T tubules

114

What happens to T tubules once they’ve been depolarised?

Voltage sensor proteins of the T tubules change their confirmation

115

What is activated due to the change in T tubule conformation?

Gated Ca 2+ -release channel of adjacent terminal cisternae

116

What happens once the Gated Ca 2+ -release channels are activated?

Ca 2+ is released rapidly from terminal cisternae into sarcoplasm

117

What happens when Ca 2+ is released into the sarcoplasm?

It binds to the TnC subunit of troponin, activating the contraction cycle

118

What happens to Ca 2+  in the sarcoplasm once it has performed it’s function?

It is returned to the terminal cisternae of the sarcoplasmic reticulum

119

What features do cardiac muscle fibres have?

- Striations 
- Centrally positioned nuclei 
- Intercalated disks
- Branching

120

How many nuclei do cardiac muscle fibres have per cell?

1 or 2

121

What is the purpose of intercalated discs?

For electrical and mechanical coupling with adjacent cells

122

How does cardiac muscle differ from skeletal muscle?

Distinct myofibrils are absent

123

What is present instead of distinct myofibrils in cardiac muscle?

Myofilaments of actin and myosin form continuous masses in the cytoplasm

124

What arrangement do intercalated disks have?

Step like

125

What do intercalated discs act as substitutes for?

Z bands where cells meet end to end

126

What junctions to intercalated discs have?

#NAME?

127

What is the purpose of gap junctions in intercalated disks?

Electric coupling

128

What is the purpose of adherens-type junctions?

To anchor cells and provide anchorage for actin filaments

129

How to the T tubules of cardiac muscle differ from those in skeletal muscle?

They lie in register with the Z bands, and not the A-I junction

130

What does the close association of the sarcoplasmic reticulum and T tubules at diads permit?

The release of ionic calcium into the sarcoplasm and subsequent muscle contraction

131

What do all cardiac muscle cells exhibit?

Spontaneous rhythmic contraction

132

Where is the spontaneous rhythmic contraction of cardiac muscle cells evident?

In embryonic cardiac muscle and in isolated mature muscle cells in tissue culture

133

How are action potentials generated in the heart?

In the sinoatrial node

134

What happens once an action potential has been generated in the sinoatrial node?

It passes to the atrioventricular node, and from there to the ventricles

135

How are nerve impulses carried in the heart?

By specialised myocardial cells called Purkinje fibres

136

What cells make up the Purkinje fibres?

Distal conducting cells

137

What do tracts of Purkinje fibres do?

Transmit action potentials from ventricles from the AV node

138

In what cells are Purkinje fibres large?

Those with; 
- Abundant glycogen
- Spare myofilaments
- Extensive gap junction sites

139

Do Purkinje fibres conduct impulses faster or slower than cardiac muscle fibres?

Faster

140

What does the rapid conduction of Purkinje fibres enable?

Ventricles to contract in a synchronised manner

141

What shape are smooth muscle cells?

Fusiform

142

What features do smooth muscle cells not have?

- Striations 
- Sarcomeres
- T tubules

143

What does contraction of smooth muscle rely on?

Actin-myosin interactions

144

Describe the contraction of smooth muscle compared to skeletal and cardiac?

Slower, more sustained, requires less ATP

145

What is the cause of the differences in contraction of smooth muscle?

Due to latch system

146

How long can smooth muscles remain contracted for?

Hours or days

147

Can smooth muscles be stretched?

Yes

148

What stimuli do smooth muscles respond to?

- Nerve signals
- Hormones 
- Drugs
- Local concentration of blood gases

149

What structures do smooth muscles form?

#NAME?

150

What walls do smooth muscles often form?

Contractile walls of passageways or cavities

151

What do contractile walls have the ability to do?

Modify volume

152

Where are contractile walls found?

- Vascular systems 
- Gut 
- Respiratory tract
- Genitourinary system

153

Where can smooth muscle be of clinical significance?

- High blood pressure
- Dysmenorrhea 
- Asthma 
- Atherosclerosis 
- Abnormal gut mobility

154

How can modified smooth muscle cells occur?

- Singly as myoepithelial cells 
- As myofibrast cells

155

What are myoepithelial cells?

Stellate cells forming a basketwork around the secretory units of some exocrine glands

156

Give 4 examples of where myoepithelial cells are found

- Sweat glands
- Salivary glands 
- Mammary glands 
- Ocular lens

157

What does contraction of myoepithelial cells around glands do?

Assists secretion of sweat, saliva or milk into secretory ducts

158

What is the purpose of myoepithelial cell contraction in the ocular lens?

Dilates the pupil

159

What do myofibroblasts do?

Produce collagenous matrix at sites of wound healing, and also contract

160

What are most smooth muscle cells innervated by?

Autonomic nervous system fibres

161

What do the autonomic nervous system fibres that innervate smooth muscle cells do?

Release their neurotransmitters from varicosities into a wide synaptic cleft

162

How are smooth muscles thick and thin filaments arranged?

Diagonally within cells, spiralling down the long axis

163

What is the result of the arrangement of the filaments in smooth muscle?

It contracts in a twisting way

164

What do intermediate filaments in smooth muscle attach to?

Dense bodies

165

Where are dense bodies found?

Scattered throughout the sarcoplasm, and occasionally anchor into the cytoplasm