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Histology > Muscle > Flashcards

Muscle Flashcards

1
Q

what is a myocyte

A

an individual muscle cell

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2
Q

what is the sarcoplasm

A

cytoplasm of a muscle cell

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3
Q

what is the sarcolemma

A

plasma membrane of a muscle cell

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4
Q

what are the 3 types of muscles

A

skeletal, smooth, and cardiac

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5
Q

what is are muscle cells derived from

A

mesoderm

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6
Q

what is the function of skeletal muscle

A

movement of skeleton, under voluntary motor control

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7
Q

describe skeletal muscle cells

A

-multinucleate, large cytoplasm, striations, “irregular polygon shaped”

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8
Q

what are syncytia

A

muscle cells formed from fusion of myoblasts into multinucleate myotubes

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9
Q

what do myotubes do

A

synthesize contractile proteins which assemble into sarcomeres

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10
Q

what happens when nuclei of skeletal muscle cells move to the periphery of the cell

A

they lose their ability to proliferate

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11
Q

what are the layers in skeletal muscle organization

A

endomysium, perimysium, and epimysium

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12
Q

what does the endomysium cover

A

individual muscle fibers

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13
Q

what does the perimysium surround

A

fascicles

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14
Q

what are fascicles in muscle cells

A

several muscle fibers bound together

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15
Q

what makes up muscle

A

many fascicles together

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16
Q

what does the epimysium surround

A

the entire muscle

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17
Q

where are blood vessels and nerves found in skeletal muscle cells

A

they follow the epimysium and perimysium

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18
Q

what type of nerve innervate fast muscle fibers

A

fast nerves

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19
Q

what type of nerves innervate slow twitch muscle fibers

A

slow nerves

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20
Q

what types of myosin are there

A

fast and slow

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21
Q

describe type 1, slow twitch muscle fibers

A

-small fibers
- large amounts of myoglobin
- large number of mitochondria
-resistant to fatigue but only generate moderate muscle tension
- common in peripheral limbs

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22
Q

what type of respiration do type 1 slow twitch muscle fibers use

A

aerobic respiration for oxidative metabolism

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23
Q

describe type 2, fast twitch muscle fibers

A

-large fibers with less myoglobin and fewer mitochondria
- lots of glycogen
- extensive sarcoplasmic reticulum for rapid Ca release
- fatigue rapidly but generate high tension for short bursts of activity

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24
Q

what type of respiration do type 2 slow twitch fibers use

A

anaerobic glycolysis

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25
Q

why do type 2 fibers fatigue rapidly

A

because they use anaerobic respiration and have a low amount of mitochondria

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26
Q

what color are type 1 fibers

A

dark red

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27
Q

what color are fast twitch fibers

A

pink/tan

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28
Q

what are the intermediate muscle fibers

A

-type 2a
-type2b

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29
Q

describe type 2a fibers

A

oxidative and fatigue resistant

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30
Q

describe type 2b fibers

A

glycolytic and fatigue resistant

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31
Q

what type of respiration do both muscle fiber types use in peak periods of exertion and why

A

anaerobic respiration because they cant get enough oxygen

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32
Q

what does lactic acid build up do to muscle

A

forms crystal precipitates in muscle tissue that tear the fibers causing soreness after heavy exertion

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33
Q

what does severe oxygen debt cause

A

ischemia, muscle cramps, and even cell death

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34
Q

what is rhabdomyolysis

A

breakdown of actin and myosin as a result of extreme exertion

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35
Q

what can rhabdomyolysis be followed by and how

A

kidney failure (myoglobinuric nephrosis) due to release of myoglobin and clogging of glomeruli

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36
Q

how do muscle cells increase in size/hypertrophy

A

increase in number of mitochondria, and increase in volume of contractile proteins causes splitting/branching of individual muscle fibers

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37
Q

how often are new muscle fibers produced

A

relatively rarely

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38
Q

what is atrophy caused by

A

immobilization, denervation, and age

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39
Q

what happens in sacropenia

A

loss of skeletal muscle fibers that are not replaced. decrease in number of fibers and muscle mass

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40
Q

what do satellite cells do

A

regenerate skeletal muscle, they are small myogenic cells adjacent to sarcolemma

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41
Q

what do satellite cells do following injury

A

proliferate and differentiate into myoblasts

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42
Q

what are the types of proprioceptors in muscle cells

A

neuromuscular spindles and neurotendinous spindles

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43
Q

what are intrafusal fibers

A

modified skeletal muscle fibers associated with modified nerve endings

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44
Q

what do neuromuscular spindles sense and where are they located

A

sense changes in length and are located within the belly of muscle

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45
Q

what do neurotendinous spindles sense and where are they located

A

the sense changes in tension and they are located within the tendon

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46
Q

what do mechanoreceptors in muscle tissue do

A

prevent overstretching and tearing of muscles, used in postural reflexes and coordination

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47
Q

what is the ultrastructure in muscle cells

A

individual muscle fibers composed of myofibrils

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48
Q

what are myofibrils composed of

A

myofilaments or contractile proteins in parallel bundles

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49
Q

what are the 2 types of myofilaments

A

actin (thin) and myosin (thick)

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50
Q

what is the ratio of actin to myosin in skeletal muscle

A

2:1

51
Q

what gives rise to the striated appearance of muscle tissue

A

parallel arrangement of contractile proteins

52
Q

where do actin and myosin overlap

A

in the A band

53
Q

what are sarcomeres

A

functional units of muscle cells that are arranged myofibrils

54
Q

what do Z-discs do

A

act as anchoring points for actin myofilaments

55
Q

what happens in the sliding filament theory of muscle contraction

A

during muscle contraction, sarcomeres shorten, but myofilaments remain the same length

56
Q

what happens when thick and thin filaments slide over one another

A

-use energy via ATP
- shortening of sarcomere from binding and unbinding of actin and myosin filaments

57
Q

what is the NMJ

A

site where skeletal muscle innervated by motor nerves

58
Q

what is the motor end plate

A

the dilated terminal portion of the axon surrounded by myelin

59
Q

what is the difference between a motor end plate and a terminal bouton

A

the motor end plate is myelinated

60
Q

what is the synaptic cleft

A

space between motor end plate of nerves and sarcolemma of muscles

61
Q

what neurotransmitter is released at the synaptic cleft on the NMJ

A

generally acetylcholine

62
Q

what happens in the electrical stimulation of a neuron

A

-influx of Na+ into neuron
-wave of depolarization down axon
- release of NT
- binding to receptor proteins
-wave of depolarization of muscle fiber

63
Q

what do transverse tubules do (T tubules)

A

extensive network of tubules continuous with sarcolemma that indirectly links extracellular space with ER and intracellular environment
- carries depolarization wave to the inside of the muscle cell cytoplasm

64
Q

what are the ends of t tubules bound by

A

terminal cisternae of ER on both sides

65
Q

what makes up a triad

A

a t tubule surrounded on both sides by cisternae

66
Q

what act as Ca resevoirs in muscle tissue

A

sarcoplasmic reticulum and terminal cisternae

67
Q

what is the mechanism for Ca release from ER and terminal cisternae into cytoplasm

A

influx of Na+ ions into cytoplasm from T tubules triggers depolarization of sarcolemma which triggers release of Ca

68
Q

what does the sliding filament mechanism result in

A

muscle contraction

69
Q

what are the steps in the sliding filament mechansim

A
  • Ca causes conformational change in troponin, which interacts with tropomyosin molecules on actin to expose myosin binding sites on the actin filament
  • myosin binding causes conformational change in myosin head and sliding of myosin past actin
  • myosin heads repeatedly bind and unbind to actin in presence of Ca and Pi, causing contraction
70
Q

what is a graded response

A

the strength of the overall contraction calculated by the total number of muscle fibers contracting at any given time

71
Q

what is a motor unit

A

a group of muscle fibers supplied by single motor neuron

72
Q

what does the stimulation of a motor neuron result in

A

contraction of all muscle fibers within that motor unit

73
Q

what is recruitment

A

increase in number of motor units firing within a muscle

74
Q

what does recruitment lead to

A

a graded response

75
Q

what is muscular dystrophy

A

-degenerative wasting disease
- muscle weakness due to genetic defect in muscle protein and then muscle cell death
- most commonly affected muscle protein: dystrophin-

76
Q

what is myasthenia gravis

A

autoimmune disease cause by production of antibodies to Ach receptors which leads to muscle weakness

77
Q

how is myasthenia gravis treated

A

with AcHase inhibitors

78
Q

describe inherent contractility in skeletal muscle

A

rhythmic, wave-like contractions independent of neurological stimulation

79
Q

describe the orientation of smooth muscle fibers and function

A

highly irregular branching fascicles specialized for long contractions with low force

80
Q

describe the size of smooth muscle fibers and the nuclei

A

smaller than skeletal muscle and the nucleus is long, single and central

81
Q

how do you tell the difference between smooth muscle and skeletal muscle

A

the nucleus in smooth muscle is single and central

82
Q

how do you distinguish between connective tissue and smooth muscle

A

-nuclei are long and ovular, the ends of nuclei are rounded and fibers are uniform in size in smooth muscle

83
Q

what is the ratio of actin to myosin filaments in smooth muscle

A

15:1, randomly arranged

84
Q

why are there no striations in smooth muscle

A

because myofilaments are not arranged in sarcomeres

85
Q

what are dense bodies

A

functionally equivalent to z-discs in smooth muscle, provide attachment sites for actin

86
Q

what does smooth muscle fibers use that controls myosin binding

A

calmodulin

87
Q

what are caveolae

A

invaginations in membrane of smooth muscle cells. smooth muscle cells use these instead of the t-tubule/terminal cisternae system. rely on extracellular calcium for contraction

88
Q

what type of innervation does skeletal muscle have

A

sympathetic and parasympathetic

89
Q

what does a single unit of muscle fibers do and what is the example

A

fibers contract as a unit ex: visceral smooth muscle of gut

90
Q

what does a multi unit of smooth muscle do and example

A

individual muscle fibers contract independently ex: erector pili muscle

91
Q

can smooth muscle repair itself after injury

A

yes

92
Q

what does smooth muscle develop from

A

endothelial cells, pericytes of blood vessels, fibroblasts

93
Q

what can glandular epithelial cells differentiate into

A

myoepithelial cells

94
Q

what is the CT layer called that surrounds the heart

A

pericardium

95
Q

what are the layers of the pericardium and what do they contain

A

outer fibrous CT layer and inner serous layer containing mesothelial cells

96
Q

what does the pericardium contain and what is its function

A

pericardial fluid for lubrication

97
Q

what are the 3 layers of the heart

A

epicardium, myocardium and endocardium

98
Q

what is the epicardium of the heart made of

A

simple squamous mesothelium

99
Q

what is the epicardium supported by

A

the underlying fibroblastic CT and adipose tissue

100
Q

where are the blood vessels and nerves located

A

within the subepicardial layer

101
Q

what is the heart surrounded by

A

adipose tissue

102
Q

where is the myocardium thickest

A

in the ventricles compared to atria

103
Q

describe the myocardium

A

thick, collagenous, connective tissue skeleton made of fibroblasts and collagen

104
Q

describe cardiac muscle fibers

A

have one centrally located nucleus (occasionally 2), fibers are striated but involuntary

105
Q

describe the arrangement of cardiac muscle

A

contractile proteins are arranged into sarcomeres, contain a diad of one t-tubule and one cisterna of ER located at z-disc

106
Q

where is endocardium found and what kind of cells are they

A

lines atria and ventricles, ccovers heart valves; simple squamous endothelium

107
Q

what supports endocardium

A

subendothelial fibroblastic CT, with reticular fibers and smooth muscle

108
Q

where is the endocardium the thickets

A

in atria compared to ventricles

109
Q

where are purkinjie fibers located

A

subepi and endocardial layers

110
Q

what do cardiac valves contain

A

layer of fibrous connective tissue called lamina fibrosa covered by endothelium

111
Q

what are valves surrounded by

A

tough, fibrous rings at base of aorta and pulmonary artery, AV valves and extending into IVS

112
Q

what is os cordis

A

at the base of AV valves when valves occasionally ossify to form bony rings

113
Q

what is inherent automaticity

A

cardiac myocytes can contract themselves without external stimulation

114
Q

what are intercalated discs

A

unique to cardiac muscle, special connections between the cells

115
Q

what do intercalated discs do

A

enhance spread of contractile stimulus between cells and allow synchronous contractions, increase SA for attachment of myofibrils between adjacent cells

116
Q

what are the types of cell junctions

A

desmosomes, fascia adherens, and gap junctions

117
Q

what do desmosomes do

A

bind individual myocytes together laterally and on ends

118
Q

what do fascia adherens do

A

like zonuls adherens but joins ends of muscle fibers

119
Q

what do gap junctions do and where are they located

A

located laterally, provide ioninc communication between cells, synchronize contractions and allow muscles to behave as a syncitium

120
Q

what does the cardiac conduction system look like

A

SA node, AV node, Bundle of His, and purkinje fibers

121
Q

describe the cells surrounding the conduction system of the heart

A

they are larger surrounding cardiac conduction systems and conduct impulses 4x faster
-paler staining around these structures due to higher glycogen content

122
Q

what is the pacemaker of the cell and where is it located

A

SA node located at junction of superior vena cava and RA

123
Q

what does the SA node do

A

generates impulses that induce contraction of atria
-as impulses travel across atria, stimulate AV node
-delays impulses, give atria time to contract
-impulse travels down IVS via bundle of His, branches into L and R AV bundles within IVS
- fibers divide into ventricular myocardium and ramify into purkinje fibers within subendo and subepicardium of ventricular free wall, gradually merge with myocardium, initiate ventricular contraction

124
Q

what does sympathetic and parasympathetic stimulation do in the SA node

A

-sympathetic stimulation from sympathetic ganglia increase HR
- parasympathetic stimulation from vagus nerve decreases HR

Histology (27 decks)

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