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Locomotor System > Histology: Muscular Tissue > Flashcards

Histology: Muscular Tissue Flashcards

1
Q

What is the purpose of muscle tissue?

A
  • allow for movement of the organism
  • allow for changes in the sizes and shapes of internal organs
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2
Q

What is muscle tissue characterised by?

A

aggregates of specialized elongated cells, arranged in parallel array (having the primary role of contraction).

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3
Q

What is the primary purpose of specialized muscle cells?

A

contraction

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4
Q

What are the major types of muscle?

A
  • skeletal muscle
  • cardiac muscle
  • smooth muscle
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5
Q

What is the most common type of muscle tissue?

A

skeletal muscle

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6
Q

What is skeletal muscle attached to?

A

bones

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7
Q

What is skeletal muscle responsible for?

A

movements of the organism

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8
Q

Is skeletal muscle voluntary or involuntary?

A

voluntary

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9
Q

Is smooth muscle voluntary or involuntary?

A

involuntary

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10
Q

Is cardiac muscle voluntary or involuntary?

A

involuntary

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11
Q

Where is smooth muscle tissue found?

A

in internal organs (eg. digestive tract, intestines, urinary bladder, blood vessel walls)

intestines: smooth muscle allows for peristalsis to occur

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12
Q

Where is cardiac muscle tissue found?

A

the heart

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13
Q

What is cardiac muscle tissue responsible for?

A

contractions of the heart

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14
Q

What is the largest muscle fiber?

A

skeletal muscle

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15
Q

What are the special features of skeletal muscles?

A

1) multinucleated
2) highly striated

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16
Q

What do skeletal muscles contain to maintain their cell sizes?

A

multiple nuclei

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17
Q

What are muscle fibers?

A

large, single, multinucleates cells

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18
Q

Where are the nucleuses of skeletal fibers found?

A

at the cell periphery

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19
Q

How sparsely are the nucleuses of skeletal muscles positioned?

A

approximately one nucleus every 35 micrometers (along the fiber)

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20
Q

How large can skeletal mucle cells get?

A

0.5 meters in length

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21
Q

What are the cells in muscle tissues called?

A

muscle FIBERS

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22
Q

Why are muscle cells called muscle “fibers”?

A

because of their long length (to describe their looks).

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23
Q

What is a distinctive feature of skeletal muscle?

A

all cell nucleuses are located on the periphery

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24
Q

Where is the nucleus positioned in a cardiac cell?

A

in the center

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25
Q

What allows for the quickest distinction between different muscle cells?

A

the position of the nucleus

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26
Q

Why do skeletal muscle fibers contain multiple nucleuses?

A

skeletal muscle fibers are formed by the fusion of many mononucleated cells (myoblasts) during development and growth

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27
Q

What cells fuse to create skeletal muscle fibers?

A

myoblasts

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28
Q

What is the muscle fiber length the same as?

A

Muscle fibers are the same length as the muscle they compose

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29
Q

What is a myofibril?

A

the structural and functional subunit of the muscle fiber

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30
Q

What is a myofibril composed of?

A

myofillaments

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31
Q

What do myofillaments contain?

A

myosin-containing thick fillaments and actin-containing thin fillaments

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32
Q

What do thick fillaments contain?

A

myosin

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33
Q

What do thin fillaments contain?

A

actin

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34
Q

What integrates with what in some particular places?

A

myosin integrates with actin in some particular places

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35
Q

What is the difference between the dark zone and light zone of a myofillament? What makes up each zone?

A

dark zone: myosin and actin fillaments
light zone: myosin only

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36
Q

In longitudinal sections, what appearance do muscle fibers have?

A

stripy

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37
Q

What does the stripy appearance of muscle fibers originate from?

A

the arrangement of repeating units (sacromeres) in series along the fiber.

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38
Q

What is the repeating unit of a muscle fiber called?

A

sarcomere

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39
Q

What is the average length of a sarcomere?

A

2.5 micrometers

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40
Q

How many sarcomeres does a 30cm fiber contain?

A

120 thousand sacromeres

1 sacromere = 2.5 micrometers

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41
Q

What are sarcomeres?

A

the smallest contractile units of striated muscles

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42
Q

What does the arrangement of thick and thin fillaments give rise to?

A

density differences which produce cross strations of the myofibril

43
Q

What do density differences of the myofibril produce?

A

cross-striations

44
Q

What is the name of the band which contains mainly the thin fillaments?

A

the “I band”

45
Q

What is the name of the band which contains mainly the thick fillaments?

A

the “A band”

46
Q

What is the name of the disk located in between the individual sarcomeres?

A

the “Z disk”

47
Q

What represents a series of coupled biochemical and mechanical events between myosin heads and actin molecules? What does it lead to?

A

the “ACTOMYOSIN CROSS-BRIDGE CYCLE”
- leads to muscle contraction

48
Q

Are muscle fibers differentiated? Do they undergo mitosis?

A

muscle fibers are:
- terminally differentiated
- do not undergo mitosis

49
Q

What are satellite cells?

A

skeletal muscle stem cells, able to repair damaged muscle fibers

50
Q

What is the name of the cell which is able to repair damaged muscle fibers?

A

skeletal muscle stem cells

51
Q

Where are satellite cells located?

A

under the basal lamina of muscle fibers

52
Q

What happens when a skeletal muscle is damaged?

A

satellite cells are stimulated to divide to generate new myoblasts, which fuse and repair the damaged muscle fiber

53
Q

What can repair damaged muscle fibers?

A

new fused myoblasts

54
Q

What happens to satellite cells when muscle is damaged?

A

Satellite cells divide by mitosis into new myoblasts which fuse to regenerate the muscle fiber (filling the damage gaps)

55
Q

What happens if the muscle fiber damage is too large?

A

no regeneration can occur.
the muscle fiber dies.
the gap created from damaged muscle tissue is filled with connective tissue.

56
Q

What is a scar?

A

a connective tissue fillament which fills a damaged muscle

typically dense irregural connective tissue

57
Q

What type of tissue are scars usually made out of?

A

dense irregular connective tissue

58
Q

What happens during muscle growth?

A

muscle cells grow in size (no new cells are made! number of muscle cells does not increase!)

59
Q

What direction do muscle fibers go in?

A

the direction in which the muscle contracts

60
Q

What muscle is exceptional? Why?

A

The tongue, because it can contract in various directions.

61
Q

What are the main features of cardiac tissue?

A

1) uninucleated
2) striated

62
Q

What type and arrangement of contractile fillaments does cardiac muscle have?

A

same as skeletal muscle

63
Q

Is cardiac muscle striated?

A

yes

64
Q

What are cardiac muscle cells called? How do they look?

A
  • cardiac myocytes
  • short cylindrical cells
  • centrally positioned nucleus
65
Q

Where is the nucleus positioned in cardiac muscle cells?

A

in the center

66
Q

What are cardiac muscle cells connected by? what do they form when connected?

A

connected by intercalated disks, to form a cardiac muscle fiber

67
Q

What do intercalated disks represent?

A

highly specialised cell-to-cell adhesion junctions

68
Q

How to distinguish cardiac mucle from skeletal muscles?

A
  • cardiac muscle cells are called CELLS not fibers!
  • cardiac muscle cells have intercallated disks
  • cardiac muscle cells have their nucleus positioned in the center, which skeletal muscle fibers have it on the periphery.
69
Q

What do cardiac myocytes look like?

A

cocacola can

70
Q

What do intercalated disks allow for? What would happen is there were no intercallated disks in cardiac muscle?

A
  • keep cardiac myocytes attathced to each other
  • create a strong surface barrier
  • (if the cells would detach then the heart wouldn’t be able to pump blood any longer, and the individual would die).
71
Q

How do the sarcomeres of cardiac muscle compare to the sarcomeres of skeletal muscle?

A

cardiac muscle sarcomeres are slightly shorter (2.2 micrometers) than skeletal muscle sarcomeres (2.5 micrometers).

72
Q

How do the cardiomyocytes compare to skeletal muscle fibers? State the length and diameter of cardiomyocytes.

A

cardiomyocytes are much smaller (80-100 micrometers in length, and about 15 mictometers in diameter).

73
Q

What do specialised cardiac muscle cells exhibit?

A

spontaneous rhythmic contractions

74
Q

What do specialised cardiac conducting muscle cells do?

A

generate and rapidly transmit action potentials to various parts of the myocardium

75
Q

What is special about specialised cardiac conducting muscle cells?

A

myocytes are myogenic, they act like nerves (generate their own impulses).

76
Q

What is special about cardiac myocytes?

A

completely involuntary

77
Q

What is the difference between specialised conducting myocytes, in comparison to normal myocytes?

A
  • different colour (specialised conducting myocytes are pale, soft in colour) (look like adipose tissue)
78
Q

Explain the regenerative properties of cardiac muscle.

A

can undergo:
- HYPERTROPHY: grow larger in size
- HYPOTROPHY: grow smaller in size
as a result of changing demands of the heart,

but the cells are:
- TERMINALLY DIFFERRENCIATED
and
- CANNOT DIVIDE

79
Q

Are cardiac muscle cells differentiated? Can they divide?

A
  • terminally differenciated
  • cannot divide
80
Q

What is the professional word used to explain the growing of the cardiac muscle cells?

A

hypertrophy

81
Q

What is the professional word used to explain the decrease in size of the cardiac muscle cells?

A

hypotrophy

82
Q

What is a cell in the heart which is similar to the ‘satellite cells’ in muscle tissue?

A

there is no large number of ‘stem’ cells, therefore the heart has a limited ability to regenerate when damaged.

83
Q

Why does the heart have a limited ability to differentiate when damaged?

A

there is no large number fo ‘stem’ cells in the heart

84
Q

How does heart muscle heal from a heart attack?

A

forms a scar tissue (fills the space with connective tissue)

85
Q

What is the primary unit of smooth muscle tissue? How does it look like?

A

bundles or sheets of small, elongated spindle cells with finely tapered ends.

86
Q

What are the major features of smooth muscle?

A

1) uninucleated (nucleus is positioned in the center)
2) not striated

87
Q

Why are smooth muscle cells not striated?

A

they do not contain muscle sarcomeres

88
Q

Is smooth muscle tissue striated?

A

no

89
Q

What does smooth muscle tissue contain instead of sarcomeres?

A

myosin fillaments are surrounded by arrays of actin fillaments (connected to dense bodies) in a less well-organised fashion.

  • arranged in x form where the lines are actin and the center of the x’s is the dense body, and between the x lines is the myosin.
90
Q

What types of contractions are smooth muscles specialized for?

A

slow, prolongued contractions

91
Q

What is the contraction of smooth muscle triggered by?

A
  • mechanical impulses (passive stretching)
  • electrical impulses (depolarization at nerve endings)
  • chemical impulses (hormones acting by a second messenger stimuli).
92
Q

What is the average time taken for contractions to occur in smooth muscle cells?

A

10-20 seconds

93
Q

What does the function of smooth muscle cells depend on?

A

the organ it is located in

94
Q

What is the function of vascular smooth muscle?

A

regenerate the lumenal diameter of the small arteries-arterioles

95
Q

What does the vascular smooth muscle significantly contribute to?

A

setting of the level of blood pressure

96
Q

What is the function of the smooth muscle in the digestive tract?

A

allow for contractions in a rhythmic peristaltic fashion (rhythmically forcing food through the digestive tract as the result of phasic contraction).

97
Q

What is another place apart from arteries and the digestive tract in which smooth muscle tissues are found?

A

the urinary tract (and all other internal organs)

98
Q

What happens to blood pressure when the smooth muscle tissue contracts?

A

the lumen of blood vessels decreases, increasing blood pressure.

99
Q

Which muscle cell type has the greatest capacity of regeneration?

A

smooth muscle cells

100
Q

Can smooth muscle increase in number?

A

yes, smooth muscle cells can divide

101
Q

What are the cells called which lie along the small blood vessels and divide to generate new smooth muscle cells?

A

pericytes

102
Q

What are pericytes?

A

cells which lie along the small blood vessels, and divide to generate new smooth muscle cells.

103
Q

What can smooth muscle cells undergo? hyperthrophy? hypotrophy?

A

hypertrophy (increase in size)

104
Q

What are the 2 approaches in which smooth muscle types regenerate?

A

1) neighbouring smooth muscle cells divide, and fill the damaged space
2) through pericytes (small blood vessels)

Locomotor System (19 decks)

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