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Body Logistics > Session 8: Muscle > Flashcards

Session 8: Muscle Flashcards

1
Q

What is the sarcolemma?

A

The outer membrane of a muscle cell

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2
Q

What is the sarcoplasm?

A

The cytoplasm of a muscle cell

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3
Q

Muscle tissue take on which two forms?

A

Striated muscle

Non-striated muscle

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4
Q

What two types of muscle are striated?

A

Skeletal muscle

Heart muscle

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5
Q

What muscle type is non-striated?

A

Smooth muscle

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6
Q

What are the three fibre types present in skeletal muscle?

A

Red
Intermediate
White

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7
Q

Skeletal muscle forms what connections?

A

Fascicle bundles

Tendons

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8
Q

Cardiac muscle forms what connections between cells?

A

Junctions join cells end to end

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9
Q

Smooth muscle forms what connections?

A

Connective tissue
Gap Junctions
Desmosome-type Junctions

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10
Q

Skeletal muscle is under what nervous control?

A

Somatic motor neurons

Voluntary control

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11
Q

Cardiac muscle is under what nervous control?

A

Intrinsic rhythm

Involuntary autonomic modulation

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12
Q

Smooth muscle is under what kind of control?

A

Involuntary
Autonomic
Intrinsic activity
Local stimuli

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13
Q

What kind of power is achieved through skeletal muscle contraction?

A

Rapid, forceful

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14
Q

What kind of power is achieved through cardiac muscle contraction?

A

Lifelong, variable rhythm

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15
Q

What kind of power is achieved through smooth muscle contraction?

A

Slow, sustained (rhythmic)

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16
Q

How do red filaments compare to white filaments in skeletal muscle in relation to their diameter, vascularisation and innervation?

A

Red filaments are smaller in diameter
Red filaments have a rich blood compared to white filaments
Red filaments have fewer neuromuscular junctions than white filaments

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17
Q

Red filaments have how many mitochondria relative to white filaments?

A

Red filaments have numerous mitochondria compared to white filaments

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18
Q

Red filaments have how much myoglobin compared to white filaments?

A

Red filaments have a rich supply of myoglobin compared to the white filament’s poor supply

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19
Q

What kind of contraction is achieved through contraction of red filaments relative to white filaments (Speed, strength)?

A

Red: Slow, repetitive, weaker
White: Faster, stronger

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20
Q

What enzymes are red skeletal fibres rich in?

A

Oxidative enzymes

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21
Q

What enzyme (s) are white skeletal fibres rich in?

A

ATPase

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22
Q

Myoglobin is present in which of the three muscle types?

A

Skeletal and cardiac, not smooth

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23
Q

What is myoglobin?

A

A red protein containing haem, which functions as an oxygen storing molecule, providing oxygen to working muscles

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24
Q

Under what conditions does haemoglobin especially give oxygen up to myoglobin?

A

Lowered pH (acidic conditions)

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25
Q

The individual muscle fascicles are wrapped in what?

A

Perimysium

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26
Q

The individual muscle fibres are wrapped in what?

A

Endomysium

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27
Q

What is the name of the layer of connective tissue that covers the entire muscle?

A

Epimysium

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28
Q

What are the 7 ways in which skeletal muscle can be arranged?

A 
Circular
Convergent 
Parallel
Unipennate
Multipennate 
Fusiform
Bipennate
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29
Q

Extrinsic muscles of the tongue are responsible for what?

A

Protruding, retracting and moving the tongue from side to side

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30
Q

Intrinsic muscles of the tongue are responsible for what?

A

Allowing the tongue to change shape

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31
Q

Do extrinsic muscles of the tongue attach to bone?

A

Yes

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32
Q

Do intrinsic muscles of the tongue attach to bone?

A

No

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33
Q

What accounts for the mobility of the tongue?

A

Plasticity and strength of the connective tissue

Multidirectional orientation of the muscle fibres

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34
Q

Skeletal muscles of the tongue often terminate by what?

A

Interdigitation with collagen and ECM of surrounding connective tissues

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35
Q

What is a muscle fibre?

A

A striated muscle cell

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36
Q

What is the sarcomere?

What does it consist of?

A

The structural unit of a myofibril in striated muscle
Segment from Z line to Z line
Made up of actin and myosin filaments

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37
Q

What are the A bands of the sarcomere?

How do they appear histologically?

A

The thick myosin filaments

They form the dark bands

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38
Q

What are the I bands of the sarcomere?

How do they appear histologically?

A

The thin actin filaments with no overlap
They form the light bands
I for “Isotropic’’

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39
Q

What is the M line of the sarcomere?

How do they appear histologically?

A

The middle of the sarcomere

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40
Q

What is the H zone ad how does this appear histologically?

A

The H band or zone are the non-overlapping myosin filaments

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41
Q

What are the Z lines?

How do they appear histologically?

A

The end of each sarcomere, attaching one sarcomere to the next
They appear as dark bands on histology

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42
Q

Which molecules come together to form the thin filaments of skeletal and cardiac muscle?

A

Actin
Tropomyosin
Troponin complex

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43
Q

Troponin assays are a useful tool for diagnosing what?

A

Cardiac Ischemia

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44
Q

The troponin complex is made up of what?

A

Troponin I
Troponin C
Troponin T

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45
Q

Troponin is released from ischaemic cardiac muscle within what time frame? And it must be measured within what time frame?

A

Released within: An hour

Measured within: 20 hours

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46
Q

True of false: Quantity of troponin is proportional to the degree of damage

A

False, not necessarily

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47
Q

Which enzyme did troponin supersede as a marker for myocardial infarction?

A

Creatine Kinase (CK)

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48
Q

True or false: The amount of CK is proportional to the infarct size

A

True

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49
Q

What is a major disadvantage of using CK as a marker for ischaemic cardiac muscle?

A

The enzyme is also released into the blood by damaged skeletal muscle and brain, not necessarily specialised to damage to cardiac muscle

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50
Q

Name three things that can result in a rise in plasma CK

A 
Intramuscular injection 
Vigorous physical exercise 
A fall (especially in the elderly) 
Muscular dystrophy 
Acute kidney injury
Rhabdomyolysis (severe muscle breakdown)
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51
Q

Describe the structure of an individual myosin molecule

A

Rod-like structure with two heads that protrude

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52
Q

Describe the structure of a myosin filament

A

Many individual myosin molecules whose heads protrude at opposite ends of the filament

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53
Q

Describe the structure of the actin filament

A

The actin filament forms a helix around which tropomyosin coils around. The troponin complex is attached to the tropomyosin molecule

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54
Q

In the centre of the sarcomere, the thick myosin filaments are lacking what?

A

Myosin heads

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55
Q

When in its high energy configuration, what is the myosin head doing?

A

Attaching to the actin myofilament forming a cross bridge

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56
Q

What is the importance of ionic calcium in muscle contraction?

A

Increased ionic calcium binds to troponin C of troponin which leads to a conformational change and moves tropomyosin away from myosin binding sites on actin, which means myosin can then bind

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57
Q

What occurs during the “working stroke” of muscle contraction?

A

The myosin head pivots and bends as it pulls on the actin filament, sliding towards the M line

58
Q

What happens when the myosin head is in “low-energy” configuration?

A

The new ATP attaches to the myosin head and the cross bridge detaches

59
Q

When ATP is hydrolysed into ADP and P what happens during contraction?

A

The myosin head detaches from actin and cocks back to starting position

60
Q

What is essential for the releasing of tropomyosin’s blockage of actin’s active sites?

A

Ionic calcium

61
Q

What is the neuromuscular junction?

A

Small terminal swellings of the axon that contain vesicles of acetylcholine (Ach)

62
Q

What happens during initiation of contraction of skeletal muscle?

A

The nerve impulse travels along the motor neuron axon and arrives at the neuromuscular junction

63
Q

What happens at the NMJ when a nerve impulse reaches it?

A

It releases acetylcholine (Ach) into the synaptic cleft causing local depolarisation of the sarcolemma

64
Q

During skeletal muscle contraction, what happens once the sarcolemma is depolarised by Ach release?

A

Voltage-gated Sodium channels open and sodium ions enters the cell

65
Q

General depolarisation of the sarcolemma and into T tubules causes what?

A

The voltage sensor proteins of the T tubule membrane to change their conformation and activates Ca2+ release from terminal cisternae into the sarcoplasm

66
Q

Once Ca2+ is released into the sarcoplasm, what happens?

A

Ca2+ binds to troponin C (TnC) and the contraction cycle is initiated

67
Q

Where is ionic calcium then return to following the initiation of the contraction cycle during muscle contraction?

A

The terminal cisternae of sarcoplasmic reticulum

68
Q

What is muscle fibrillation?

A

The contraction of individual muscle fibres (muscle cells)

69
Q

What is muscle fasciculation?

A

The contraction of whole muscle fascicles, often under the innervation of a single motor neurone (As in motor neurone disease)

70
Q

What are absent from cardiac muscle that are distinctly present in skeletal muscle?
What are formed instead?

A

Myofibrils

Myofilaments of actin and myosin form continuous masses in the cytoplasm

71
Q

____________ and _____________ penetrate through the cytoplasm between myofilaments

A

Mitochondria

Sarcoplasmic reticulum

72
Q

Longitudinal sections of cardiac muscle fibres show what?

A

Striations
Centrally positioned nuclei (1 or 2 per cell, no more than 2)
Intercalated discs
Branching

73
Q

Transverse sections of cardiac muscle fibres show what?

A

Centrally positioned nuclei
Endomysium
Lobular profiles of branching fibres

74
Q

Cardiac muscle fibres have what instead of the Z lines that are seen in skeletal muscle?

A

Intercalated discs

75
Q

Where are the intercalated discs of cardiac muscle?

What two types of junctions do they have?

A

Where the cells meet, end to end

Gap junctions and adherens- type junctions

76
Q

What is the purpose of the gap junctions at the intercalated discs?

A

Electrical coupling between cells to ensure that the cells contract together

77
Q

What is the purpose of the adherens- type junctions at the intercalated discs?

A

Provide anchorage for actin filaments

78
Q

What is different with regard to the arrangement of T-tubules in cardiac muscle compared to skeletal muscle?

A

The T-tubules of cardiac muscle are in lie with the Z disc rather than the A-I band junction

79
Q

What is a diad? Are these found in skeletal or cardiac muscle?

A

The point at which the t-tubule meets a single terminal cisterna of the sarcoplasmic reticulum. Cardiac muscle

80
Q

Where is the diad located in the cardiac myocyte?

A

At the Z line

81
Q

What is a t-tubule?

A

A “transverse” tubule that is a deep invaginated of the sarcolemma

82
Q

What is a triad?

A

The point at which the t-tubule meets a terminal cisterna of the sarcoplasmic reticulum on either side of it. They are found in skeletal muscle

83
Q

Where is the triad typically located in skeletal muscle?

A

Along the A-I junction

84
Q

What is the purpose of triads and diads in skeletal and cardiac muscle fibres?

A

Allows close association of t-tubules and sarcoplasmic reticulum which permits the release of ionic calcium into the sarcoplasm and subsequent muscle contraction

85
Q

What is cell hypertrophy?

A

Enlargement of individual cells without an increase in number of cells

86
Q

What is cell hyperplasia?

A

An increase in the number of cells due to mitosis

87
Q

What is heart atrophy?

A

When the heart is smaller than the normal heart due to smaller individual cells that make up the heart

88
Q

What is heart hypertrophy?

A

When the heart is bigger than the normal heart due to the larger individual cells that make up the heart

89
Q

What are natriuretic peptides?

A

Peptide hormones that are synthesised by the heart, brain and other organs in response to atrial and ventricular distension, usually in response to heart failure

90
Q

What are the main physiological actions of natriuretic peptides?

A

To reduce arterial pressure by decreasing blood volume and systemic vascular resistance

91
Q

What is ANP?

When would it be released?

A

Atrial natriuretic peptide

When the atria are distended

92
Q

Do normal hearts secrete extremely small or large amounts of ANP?

A

Extremely small amounts

93
Q

In what patients would you find elevated levels of ANP?

A

Patients with left ventricular (LV) hypertrophy and mitral valve disease
(During hypervolemic states which occur in congestive heart failure)

94
Q

What is BNP?

Where is it synthesised?

A

Brain-type natriuretic peptide

In the ventricles and the brain

95
Q

Both BNP and NT-pro-BNP are sensitive, diagnostic markers for what?

A

Heart failure in patients

96
Q

In response to cardiac distension, ANP causes what?

A

The kidney to raise glomerular filtration rate therefore excreting more sodium and water to reduce blood volume. This leads to reduction in cardiac output and systemic blood pressure

97
Q

In response to cardiac distension, BNP causes what?

A

Vasodilation which causes blood pressure to lower as well as increased natriuresis and diuresis (sodium and water excretion)

98
Q

Natriuretic peptides serve as a counter-regulatory system for what?

A

The renin-angiotesin-aldosterone system

99
Q

In the heart, action potentials are generated where?

A

In the sinoatrial node (SA node)

100
Q

Action potentials pass from the SA node to where?

A

To the atrioventricular node (AV node)

101
Q

The impulses pass from the AV node to where?

A

Ventricles

102
Q

What are the specialised myocardial cells that carry impulses to the ventricular muscle called?

A

Purkinje fibres

103
Q

Purkinje fibres relatively are small or large cells?

A

Large

104
Q

Purkinje fibres are abundant in what?

A

Glycogen

105
Q

Purkinje fibres have sparse what?

A

Myofilaments

106
Q

Purkinje fibres have extensive what between cells?

A

Gap junctions

107
Q

Do purkinje fibres conduct action potentials more or less rapidly than cardiac muscle fibres?

A

More rapidly (3-4m/s compared to 0.5m/s)

108
Q

What does the rapid conduction of action potentials by purkinje fibres enable?

A

Contraction of ventricles in a synchronous manner

109
Q

Smooth muscle cells are described as what shape? Where is the nucleus located?

A

Fusiform (Spindle-shaped)

In the centre of the cell

110
Q

Is smooth muscle striated?

A

No

111
Q

Does smooth muscle contain sarcomeres?

A

No

112
Q

Does smooth muscle contain T tubules?

A

No

113
Q

Smooth muscle contraction relies on what?

A

Actin-myosin interactions

114
Q

Why do we not see the regular banding of actin and myosin filaments in smooth muscle?

A

They are not lined up in a regular way

115
Q

Compared to other muscle types, smooth muscle contraction is what?
(In relation to speed, duration and energy-requirement)

A

Slower
More sustained
Requires less ATP

116
Q

Smooth muscle can remain contracted for _____ or ______

A

hours

days

117
Q

Is smooth muscle capable of being stretched?

A

Yes

118
Q

Smooth muscle responds to stimuli in the form of what?

A

Nerve signals
Hormones
Drugs
Local concentrations of blood gases

119
Q

Smooth muscle can form _____, bundles or ________ containing thousands of cells.

A

Sheets

Layers

120
Q

Smooth muscle often forms contractile walls of passageways or cavities in order to do what?

A

Modify the volume passing through them

121
Q

Where might you find smooth muscle?

A

Vascular structures
The gut
The respiratory tract
The genitourinary system

122
Q

Is smooth muscle voluntary or involuntary?

A

Involuntary

123
Q

When smooth muscle contracts with pathological affect it can cause what conditions?

A 
Asthma
High blood pressure 
Atherosclerosis 
IBS
Detrusor muscle instability
124
Q

Modified smooth muscle can occur singly as which two cell types?

A

Myoepithelial cells

Myofibroblast cells

125
Q

What are myoepothelial cells?

A

Stellate (Star-shaped) cells that form a basketwork around secretory units of some exocrine glands (e.g.sweat,salivary,mammary)

126
Q

Myoepithelial cells found in the ocular iris contract to do what?

A

Dilate the pupil

127
Q

What are myofibroblasts?

A

Sites of wound healing that produce collagenous matrix but also contract (they contain actin and myosin)

128
Q

In what processes are myofibroblasts prominent?

A

Wound contraction

Tooth eruption

129
Q

Most smooth muscles are innervated by what?

A

The autonomic nervous systeem

130
Q

What are varicosities?

A

Enlarged regions of autonomic nerves that release neurotransmitters into a wide synaptic cleft

131
Q

How are smooth muscle thick and thin filaments are arranged?

A

Diagonally within the cell spiralling down the long axis

132
Q

How do smooth muscle cells contract?

A

In a twisting way

133
Q

What do intermediate filaments of smooth muscle attach to?

A

Dense bodies

134
Q

Where are dense bodies found in smooth muscle?

A

Throughout the sarcoplasm and occasionally anchor to the sarcolemma

135
Q

Are calcium ions necessary for contraction of smooth muscle?

A

Yes

136
Q

What is the nature of repair possible in a mature skeletal muscle?

A

Cells cannot divide but the tissue can regenerate by mitotic activity of satellite cells
Hyperplasia follows muscle injury

137
Q

How does skeletal muscle undergo hypertrophy?

A

By satellite cells fusing with existing muscle cells to increase mass

138
Q

What is the nature of repair possible in mature cardiac muscle?

A

Cardiac muscle is incapable of regeneration

139
Q

What happens to cardiac muscle following damage?

A

Fibroblasts invade, divide and lay down scar tissue

140
Q

What is the nature of repair possible in mature smooth muscle?

A

Smooth muscle cells retain their mitotic activity and can form new smooth muscle cells

141
Q

Where is smooth muscles ability to form new smooth muscle cells particularly evident?

A

In the pregnant uterus where the muscle wall becomes thicker by hypertrophy and by hyperplasia

Body Logistics (16 decks)

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