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Z OLD Tissues of the Body > Muscle > Flashcards

Muscle Flashcards

1
Q

What is myalgia?

A

Muscle pain

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2
Q

What is myasthenia?

A

Muscle weakness

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3
Q

What is myopathy?

A

Any disease of the muscle

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4
Q

What is the sarcolemma?

A

The outer membrane of muscle cells

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5
Q

What is the sarcoplasm?

A

The cytoplasm of a muscle cell

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6
Q

What are the 3 major muscle types?

A

NAME?

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7
Q

Is skeletal muscle striated?

A

Yes

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8
Q

How big are skeletal muscle fibres?

A
  • 1mm-20cm long

- 10-100µm in diameter

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9
Q

What shape are skeletal muscle fibres?

A

Long parallel cylinders

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10
Q

Describe the nuclei of skeletal muscle cells

A

Multiple peripheral nuclei

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11
Q

How are skeletal muscles connected?

A

Fascicle bundles and tendons

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12
Q

What controls skeletal muscle?

A

Motor neurones

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13
Q

Are skeletal muscles under voluntary or involuntary control?

A

Voluntary

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14
Q

Describe the action of skeletal muscles?

A

Rapid and forceful

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15
Q

Is cardiac muscle striated?

A

Yes

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16
Q

How big are cardiac muscle fibres?

A
  • 50-100µm long

- 10-20µm in diameter

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17
Q

Describe the shape of cardiac muscle?

A

Short, branched cylinders

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18
Q

Describe the nuclei of cardiac muscle fibres?

A

Single, central nucleus

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19
Q

How is cardiac muscle contraction controlled?

A

Intrinsic rhythm, under autonomic modulation

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20
Q

Is cardiac muscle contraction voluntary or involuntary?

A

Involuntary

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21
Q

Describe the nature of cardiac muscle rhythm?

A

Lifelong, variable

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22
Q

Is smooth muscle striated?

A

No

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23
Q

How big are smooth muscle fibres?

A
  • 20-200µm long

- 5-10µm in diameter

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24
Q

What shape are smooth muscle fibres?

A

Spindle shaped, tapering ends

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25
Q

Describe the nuclei of smooth muscle cells?

A

Single central nucleus

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26
Q

How is smooth muscle joined?

A

By connective tissue, gap and desmosome-type junctions

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27
Q

How is smooth muscle controlled?

A

Autonomic, intrinsic activity, caused by local stimuli

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28
Q

Is smooth muscle contraction voluntary or involuntary?

A

Involuntary

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29
Q

Describe the nature of smooth muscle contraction

A

Slow, sustained or rhythmic

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30
Q

How is skeletal muscle developed?

A

NAME?

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31
Q

What does the myotube have?

A

A chain of multiple central nuclei

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32
Q

What happens to the chain of nuclei in myotubes?

A

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

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33
Q

What happens to myoblasts producing cardiac and smooth muscle?

A

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

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34
Q

How do skeletal muscle fibres differ from each other?

A

In their diameter and their natural colour in vivo

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35
Q

What stains corroborate the natural colour of skeletal muscle fibres?

A

Strain showing reaction to NADH in mitochondria

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36
Q

What are the 3 types of skeletal muscle fibre?

A

NAME?

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37
Q

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

A

All

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38
Q

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

A

The functional role of the muscle

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39
Q

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

A

Smaller

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40
Q

What are red skeletal muscle fibres rich in?

A
  • Myoglobin
  • Vascularisation
  • Mitochondria
  • Oxidative enzymes
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41
Q

Of what do red skeletal muscle fibres have few?

A

NAME?

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42
Q

What kind of contraction does red skeletal muscle fibres induce?

A

Slow, repetitive, weaker

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43
Q

How quickly does red skeletal muscle fatigue?

A

Slowly

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44
Q

Where are red skeletal muscle fibres found?

A
  • Limb muscles of animals
  • Postural muscles of back
  • Breast muscle of migrating birds
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45
Q

Comparatively, how big are white skeletal muscle fibres?

A

Larger

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46
Q

What do white skeletal muscle fibres have lots of?

A

NAME?

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47
Q

Of what do white skeletal muscle fibres have few?

A
  • Myoglobin
  • Vascularisation
  • Oxidative enzymes
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48
Q

What kind of contraction do white skeletal muscle fibres induce?

A

Faster, stronger

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49
Q

Where are white skeletal muscle fibres typically found?

A
  • Extra-ocular muscles

- Muscles controlling fingers

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50
Q

What links muscle to bone?

A

Tendons

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51
Q

What is the epimysium?

A

Protective sheath over muscle

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52
Q

Where does the perimysium exist?

A

Between bundles of muscle fibres

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53
Q

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

A

Outside of it

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54
Q

What are fasicles?

A

Bundles of muscle fibres wrapped by perimysium

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55
Q

Where is endomysium found?

A

Between muscle fibres

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56
Q

What are possible arrangements for muscle fibres?

A
  • Convergent
  • Circular
  • Parallel
  • Fusiform
  • Unipennate
  • Bipennate
  • Multipennate
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57
Q

Where do skeletal muscle fibres interdigitate?

A

At myotendinous junctions

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58
Q

How do skeletal muscle fibres interdigitate?

A

With tendon collagen bundles

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59
Q

Where does the sarcolemma lie?

A

Between the collagen bundles and muscle fibres myofilaments

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60
Q

What do the extrinsic muscles of the tongue do?

A

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

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61
Q

Where does the extrinsic muscles of the tongue have insertions?

A

In bone/cartilage

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62
Q

Are the intrinsic muscles of the tongue attached to bone?

A

No

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63
Q

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

A

It allows the tongue to change shape, but not position

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64
Q

How to the skeletal muscles of the tongue often terminate?

A

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

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65
Q

What accounts for the mobility of the tongue?

A

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

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66
Q

What is a striated muscle cell called?

A

A muscle fibre

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67
Q

What is the plasmalemma of a muscle cell sometimes called?

A

It’s sarcolemma

68
Q

What is the sarcomere?

A

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

69
Q

Which band appears dark?

A

A

70
Q

Which band appears light?

A

I

71
Q

What happens to the sarcomeres in the sliding filament mechanism?

A

They get shorter-

  • I band and H zone shorten
  • A band remains the same
72
Q

What are skeletal muscles composed of?

A

Fasicles

73
Q

What are fasicles composed of?

A

Muscle fibres (cells)

74
Q

What are muscle fibres composed of?

A

Myofibrils

75
Q

What are the myofibrils?

A

NAME?

76
Q

What forms the thin filaments of skeletal and cardiac muscle?

A

A complex of actin, tropomyosin and troponin

77
Q

How can troponin assays be used as a diagnostic tool?

A

Can be used as a marker for cardiac ischaemia

78
Q

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

A

I and T forms

79
Q

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

A

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

80
Q

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

A

Not necessarily

81
Q

Describe the structure of an individual myosin molecule

A

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

82
Q

What does each thick filament consist of?

A

Many myosin molecules

83
Q

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

A

At opposite ends of the filament

84
Q

What do actin filaments form?

A

A helix

85
Q

What happens to the actin helix?

A

Tropomyosin molecules coil around it

86
Q

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

A

It reinforces it

87
Q

What is attached to each tropomyosin molecule?

A

A troponin complex

88
Q

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

A

Thet are devoid of myosin heads

89
Q

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

A

They extend towards the actin filaments

90
Q

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

A
  • 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
Q

What conformational change is made on binding of calcium?

A

The troponin has moved down, taking tropomyosin with it

92
Q

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

A

Muscle contraction only occurs in the presence of calcium ions

93
Q

What is the sliding filament theory of muscle contraction?

A
  • 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
Q

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

A

High energy conformation

95
Q

What is meant by the high energy conformation of myosin?

A

It has ADP+Pi attached

96
Q

When is myosin in the low energy conformation?

A

When it has ATP attached to the head

97
Q

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

A

Means myosin is ready to bind to a new actin filament

98
Q

What causes movement of skeletal muscle?

A

Individual myosin heads attaching and flexing at different times

99
Q

What is the rigor configuration?

A

When the myosin head is bound tightly to actin molecule

100
Q

What causes rigor mortis?

A

In death, lack of ATP perpetuates the rigor configuration

101
Q

What is at the end of the axons?

A

Small terminal swellings

102
Q

What do the small terminal swellings of the axon contain?

A

Acetylcholine

103
Q

What causes the release of acetylcholine?

A

A nerve impulse

104
Q

What happens to released acetylcholine?

A

It binds to receptors on the sarcolemma

105
Q

What is the result of acetylcholine binding to receptors?

A

Initiates an action potential propagated along the muscle

106
Q

Where do nerves come from?

A

The motor neurone cell body of the spinal cord

107
Q

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

A

A motor neurone

108
Q

What happens to the motor neurone axon?

A

It branches, and joins to muscle fibres

109
Q

What initiates the contraction of skeletal muscle?

A

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

110
Q

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

A

The release of acetylcholine (ACh) into the synaptic cleft

111
Q

What does the release of ACh cause?

A

Local depolarisation of the sarcolemma

112
Q

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

A

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

113
Q

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

A

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

114
Q

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

A

Voltage sensor proteins of the T tubules change their confirmation

115
Q

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

A

Gated Ca 2+ -release channel of adjacent terminal cisternae

116
Q

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

A

Ca 2+ is released rapidly from terminal cisternae into sarcoplasm

117
Q

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

A

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

118
Q

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

A

It is returned to the terminal cisternae of the sarcoplasmic reticulum

119
Q

What features do cardiac muscle fibres have?

A
  • Striations
  • Centrally positioned nuclei
  • Intercalated disks
  • Branching
120
Q

How many nuclei do cardiac muscle fibres have per cell?

A

1 or 2

121
Q

What is the purpose of intercalated discs?

A

For electrical and mechanical coupling with adjacent cells

122
Q

How does cardiac muscle differ from skeletal muscle?

A

Distinct myofibrils are absent

123
Q

What is present instead of distinct myofibrils in cardiac muscle?

A

Myofilaments of actin and myosin form continuous masses in the cytoplasm

124
Q

What arrangement do intercalated disks have?

A

Step like

125
Q

What do intercalated discs act as substitutes for?

A

Z bands where cells meet end to end

126
Q

What junctions to intercalated discs have?

A

NAME?

127
Q

What is the purpose of gap junctions in intercalated disks?

A

Electric coupling

128
Q

What is the purpose of adherens-type junctions?

A

To anchor cells and provide anchorage for actin filaments

129
Q

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

A

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

130
Q

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

A

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

131
Q

What do all cardiac muscle cells exhibit?

A

Spontaneous rhythmic contraction

132
Q

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

A

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

133
Q

How are action potentials generated in the heart?

A

In the sinoatrial node

134
Q

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

A

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

135
Q

How are nerve impulses carried in the heart?

A

By specialised myocardial cells called Purkinje fibres

136
Q

What cells make up the Purkinje fibres?

A

Distal conducting cells

137
Q

What do tracts of Purkinje fibres do?

A

Transmit action potentials from ventricles from the AV node

138
Q

In what cells are Purkinje fibres large?

A

Those with;

  • Abundant glycogen
  • Spare myofilaments
  • Extensive gap junction sites
139
Q

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

A

Faster

140
Q

What does the rapid conduction of Purkinje fibres enable?

A

Ventricles to contract in a synchronised manner

141
Q

What shape are smooth muscle cells?

A

Fusiform

142
Q

What features do smooth muscle cells not have?

A
  • Striations
  • Sarcomeres
  • T tubules
143
Q

What does contraction of smooth muscle rely on?

A

Actin-myosin interactions

144
Q

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

A

Slower, more sustained, requires less ATP

145
Q

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

A

Due to latch system

146
Q

How long can smooth muscles remain contracted for?

A

Hours or days

147
Q

Can smooth muscles be stretched?

A

Yes

148
Q

What stimuli do smooth muscles respond to?

A
  • Nerve signals
  • Hormones
  • Drugs
  • Local concentration of blood gases
149
Q

What structures do smooth muscles form?

A

NAME?

150
Q

What walls do smooth muscles often form?

A

Contractile walls of passageways or cavities

151
Q

What do contractile walls have the ability to do?

A

Modify volume

152
Q

Where are contractile walls found?

A
  • Vascular systems
  • Gut
  • Respiratory tract
  • Genitourinary system
153
Q

Where can smooth muscle be of clinical significance?

A
  • High blood pressure
  • Dysmenorrhea
  • Asthma
  • Atherosclerosis
  • Abnormal gut mobility
154
Q

How can modified smooth muscle cells occur?

A
  • Singly as myoepithelial cells

- As myofibrast cells

155
Q

What are myoepithelial cells?

A

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

156
Q

Give 4 examples of where myoepithelial cells are found

A
  • Sweat glands
  • Salivary glands
  • Mammary glands
  • Ocular lens
157
Q

What does contraction of myoepithelial cells around glands do?

A

Assists secretion of sweat, saliva or milk into secretory ducts

158
Q

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

A

Dilates the pupil

159
Q

What do myofibroblasts do?

A

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

160
Q

What are most smooth muscle cells innervated by?

A

Autonomic nervous system fibres

161
Q

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

A

Release their neurotransmitters from varicosities into a wide synaptic cleft

162
Q

How are smooth muscles thick and thin filaments arranged?

A

Diagonally within cells, spiralling down the long axis

163
Q

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

A

It contracts in a twisting way

164
Q

What do intermediate filaments in smooth muscle attach to?

A

Dense bodies

165
Q

Where are dense bodies found?

A

Scattered throughout the sarcoplasm, and occasionally anchor into the cytoplasm

Z OLD Tissues of the Body (19 decks)

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