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Block C - Circulation > HIstology Lecture 1 -- Muscles > Flashcards

HIstology Lecture 1 -- Muscles Flashcards

1
Q

Origin of muscle fibers

A

mesodermal

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2
Q

How does differentiation occur for muscle fibers

A

Mainly by a process of cell lengthening and synthesis of myofibrillar proteins

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3
Q

3 types of muscle fibres

A

Smooth
Skeletal
Cardiac

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4
Q

Which types of muscle fibres have myofribrils that can be seen in cross section?

A

Skeletal

Cardiac

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5
Q

Which types of muscle fibres have centrally located nuclei

A

Smooth

Cardiac

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6
Q

Which types of muscle fibres have peripherally loctaed nuclei

A

Skeletal

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7
Q

Which types of muscle fibres have striations?

A

Skeletal

Cardiac

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8
Q

What is the most abundant type of muscle in the body

A

Skeletal striated muscle

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9
Q

3 coats of connective tissue that organize muscle

A

Epimysium
Perimysium
Endomysium

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10
Q

Define epimysium

A

Dense connective tissue surrounding the entire muscle

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11
Q

Define perimysium

A

Connective tissue surrounding each bundle of fibres or fascicles

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12
Q

Define endomysium

A

Thin layer of connective tissue surrounding each muscle fibre

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13
Q

What does the endomysium contain

A

Basal lamina
Associated reticular fibrils (collagen type III)
Elastic fibres
Capillaries supplying blood to muscle fibres

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14
Q

Which types of muscle fibres are involuntary?

A

Smooth

Cardiac

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15
Q

Range of muscle fibre length

A

1 - 40 mm

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16
Q

Range of muscle fibre diameter

A

10 - 100 micrometers

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17
Q

Cell membrane of muscle fibres

A

Sarcolemma

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18
Q

Cytoplasm of muscle fibres

A

Sarcoplasm

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19
Q

Define satellite cells

A

Stem cells that sit between the basal lamina and the sarcolemma. Have separate cell membrane separating them from the sarcolemma

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20
Q

Role of satellite cells

A

When needed, extra nuclei can be recruited by mitotic division = one nucleus goes into sarcoplasm and other nucleus remains in satellite cell

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21
Q

Major organelles in striated muscle fibres

A

Myofibrils
Mitochondria
Smooth endoplasmic reticulum (sarcoplasmic reticulum)

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22
Q

Describe the contraction of smooth muscles

A

Slow and involuntary (i.e. wall of digestive system, blood vessels, uterus)

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23
Q

Describe the contraction of striated skeletal muscle

A

Quick, forceful, usually voluntary

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24
Q

Describe the contraction of striated cardiac muscle

A

Voluntary, vigorous, rhythmic

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25
Q

In what types of muscle can hypertrophy occur?

A

Skeletal

Cardiac

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26
Q

In what types of muscle can hyperplasia occur&

A

Smooth muscle

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27
Q

Function of connective tissue in skeletal muscle

A

Mechanical transducer to the forces generated by the contracting muscle cells

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28
Q

Approximate number of myofibrils in one muscle fibre

A

1500

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29
Q

Diameter of myofibrils

A

1 - 2 micrometers

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30
Q

Approximate number of thin filaments in one myofibril

A

3000

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31
Q

Approximate number of thick filaments in one myofibril

A

1500

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32
Q

Define the sarcomere

A

The smallest repetitive subunit of the contractile appartus extending from Z line to Z line

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33
Q

Approximate size of one sarcomere

A

2 - 3 micrometers

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34
Q

whats does the M line contain?

A

Creatine kinase

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35
Q

Creatine kinase purpose

A

Catalyze this reaction:

phosphocreatine + ADP –> ATP + creatine

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36
Q

What does the Z line contain?

A

alpha actininin

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37
Q

Purpose of alpha actinin

A

Anchor actin filamtents

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38
Q

What are thin filaments comprised of

A

Polymerized F-actin (from free G-actin)

Tropomyosin and troponin

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39
Q

What are thick filaments comprised of

A

Myosin

Titin

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40
Q

White distinguishes red, white and intermediate muscle fibres?

A

The amount of oxygen binding protein myoglobin and mitochondrial content

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41
Q

Define red fibres

A

Slow-twitch motor units resistant to fatigue

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42
Q

Location of red muscle fibres

A

Postural muscles of limbs and back

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43
Q

Define white muscle fibres

A

Fast twitch motor units that fatigue rapidly but give strong contractions

44
Q

Examples of white muscle fibres

A

Leg and arm muscles or breast muscles in chickens

45
Q

Compare red and white muscle fibres

A

Red is smaller than white and contains more myoglobin and mitochondria

46
Q

Define T-tubules (transverse tubules)

A

Invaginations of the sarcolemma

47
Q

What surrounds individual myofibrils?

A

Hollow tubules collectively referred to as the sarco-tubular apparatus

48
Q

Define sarcoplasmic reticulum

A

A network of canals running in parallel with the sarcomere filaments, transverse to the T-tubules

49
Q

What does one section of a sarcoplasmic reticulum span? What is its boundary?

A

The legnth of one sarcomere, bounded by (but not continuous with) a T-tubule

50
Q

WHere are terminal cisternae found?

A

Where the sarcoplasmic reticulum abuts the transverse tubules

51
Q

Define a triad

A

A T-tubule with its two adjoining terminal cisternae

52
Q

What causes the characteristic cross-striations in skeletal muscle?

A

Differences in refractive indices associated with different components of the sarcomere units on each myofibril and their register from myofbril to myofibril

53
Q

Which bands of the sarcomere change shape during muscle contractions?

A

H pseudoband, I band

54
Q

What is each myosin molecule composed of

A

A dimer composed of two tightly intertwined heavy polypeptide chains consisting on L-meromyosin (LMM)

55
Q

What is at the end of each myosin chain?

A

Globular head attached by a short elastic stalk, both made of H-meromyosin (HMM)

56
Q

Which subtype of HMM forms the globular head? The neck?

A 
S-1 = head
S-2 = short neck
57
Q

What are the myosin globular heads associated with?

A

A pair of “light” polypeptide chains (L1 and L2)

58
Q

What do the myosin heads contain?

A

Specific binding sites for actin
ATP receptor site
Catalytic sit capable of hydrolyzing ATP

59
Q

Function of titin

A

Anchor the ends of thick filaments to the Z lines

60
Q

2 regulatory proteins associated with actin

A

Tropomyosin and troponin

61
Q

Ratio of actin to tropomyosin and troponin in skeletal muscle

A

7:1:1

62
Q

3 proteins that comprise troponin

A

TN-I
TN-T
TN-C

63
Q

TN-T purpose

A

High affinity for tropomyosin

64
Q

TN-I purpose

A

High affinity for actin

65
Q

TN-C purpose

A

Calcium acceptor proteins that simultaneously binds to TN-T or TN-I

66
Q

Role of troponin in absence of free calcium

A

Inhibitory role by keeping the actin-tropomyosin filaments in a configuration that masks specific myosin binding sites on the actin molecule (cross-bridge formation)

67
Q

Define Nebulin

A

A giant protein molecule, two of which wrap around actin filaments in skeletal muscle, that is a part of the muscle cell’s cytoskeleton

68
Q

Nebulin function

A

Regulate the assembly of the actin filament
Stabilize the length of the actin filament
Help anchor actin filament to the Z-line

69
Q

Neurotransmitter found in the pre-synaptic vesicle of the neuromuscular junction

A

Acetylcholine

70
Q

Effect of acetylcholine on the sarcolemma

A

Cause a local increase in the permeability of the sarcolemma = depolarization of the membrane

71
Q

3 layers of the wall of the heart

A

Epicardium
Myocardium
Endocardium

72
Q

2 layers of the pericardium

A

Fibrous pericardium

Inner serious pericardium

73
Q

2 layers of the serious pericardium

A

Parietal lamina

Visceral lamina

74
Q

Define the fibrous pericardium

A

An external layer offibrous connective tissue

75
Q

Constituents of the endocardium

A

Smooth thin membrane consisting of:
Endothelium
Connective and smooth muscle tissue

76
Q

Location of striated involuntary cardiac muscle fibres

A

Walls of the heart and the base of the pulmonary veins

77
Q

How are individual cardiac cells attached to each other

A

Junctional complexes called intercalated discs

78
Q

2 parts of the intercalated disc

A

Transverse

Lateral

79
Q

Define the transverse part of the intercalated disc

A

The physical connection part consisting of:
Desmosomes
Adherens jjunctions (fascia adherens)

80
Q

Define the lateral part of the intercalated disk

A

Communicating part consisting of a gap junction

81
Q

Function of the gap junction

A

Provide a means of passing ionic signals from one cell to another = heart has a synchronous beat

82
Q

What regulates the synchronization of the heart

A

Modified cardiac myocytes called Purkinje fibres

83
Q

What do the secretory granules of the cardiac muscle fibres of the atria contain?

A

Atrial natriuretic factor

Brain natriurietic factor

84
Q

Function of the natriurietic factors found in the cardiac muscle fibres of the atria

A

Diuretics that inhibit renin secretion in the kidney
Relax vascular smooth muscle
Also, brain natriuretic factor increases in CHF

85
Q

Describe the nucleus of smooth muscle fibres

A

Centrally placed, elongated, sausage-shaped

Seen as a corkscrew shape when contracted

86
Q

What surrounds each smooth muscle fibre?

A

Basal lamina (except at gap junctions)

87
Q

What surrounds the basal lamina of smooth muscles?

A

Reticular fibres

Elastic fibrils

88
Q

Equivalent of T-tubules in smooth muscle fibres

A

Caveolae

89
Q

Where do the components of the reticular fibres and elastic fibrils of smooth muscle fibres come from?

A

Components are secreted by the smooth muscle cells (collagen type III and IV)

90
Q

Where are the longest smooth muscle fibres

A

Gravid uterus

91
Q

The 3 types of filaments found in the smooth muscle sarcoplasm

A

Thin filaments
Intermediate filaments
Thick filaments

92
Q

Components of smooth muscle thin filaments

A

Actin

Tropomyosin

93
Q

Where do smooth muscle thin filaments arise from?

A

Dense patches or dense bodies that are either membrane associated or free in the sarcoplasm

94
Q

What do the smooth muscle dense bodies contain?

A

Alpha actinin

95
Q

Describe smooth muscle intermediate filaments

A

Attached to dense patches

10 nm in diameter, extend between dense patches

96
Q

Component of all smooth muscle intermediate filaments

A

Desmin

97
Q

Component of vascular smooth muscle intermediate filaments

A

Vimentin

98
Q

How are the thick filaments arranged in smooth muscle?

A

Lie parallel to thin filaments

99
Q

What are smooth muscle thick filaments made of?

A

Myosin II

100
Q

List the 5 steps of muscle contraction (post-membrane depolarization)

A

1) Ca influx from ER
2) Bind TnC
3) Myosin binds actin –> cleave ATP
4) Myosin head slides thin over thick filament
5) Ca removed by ER (let go)

101
Q

What mutation causes muscular dystrophy?

A

Mutations in the laminin gene

102
Q

Define myasthenia gravis

A

Autoimmune disease due to the presence of auto-antibodies against the acetylcholine receptor

103
Q

What is one connexon comprised of?

A

6 connexins (connexin 48)

104
Q

What is the consequence of connexin 48 mutations?

A

Lethal (kill fetus)

105
Q

Describe the inactive state of myosin filaments in smooth muscle

A

Non-phosphorylated light chains cause binding of head to tail = looped filament

106
Q

What is the reaction to activate myosin filaments?

A

Calcium-mediate myosin light chain kinase causing ATP -> ADP

107
Q

What connective tissue layers does smooth muscle contain?

A

Endomysium only

Block C - Circulation (26 decks)

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