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Whitney - Histology Test 2 > Lecture 17 Skeletal Muscle Tissue > Flashcards

Lecture 17 Skeletal Muscle Tissue Flashcards

1
Q

What are the three muscle types?

A

Skeletal, Smooth, and Cardiac

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2
Q

Skeletal Muscle Characteristics

A 
Multinucleated syncytium 
Peripheral nuclei
Sarcomeric arrangement 
Each fiber innervated via a single motor axon
"all or none" contraction
Troponin C
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3
Q

Formation of skeletal muscle cells (fibers)

A

Formed during embryonic development; hundreds of individual mononucleated myoblasts join end to end to form a myotube
Myotube matures into cylindrical myocyte w/ hundreds of nuclei

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4
Q

Describe Type I Myofibers

A 
Intense staining for oxidative enzymes
Rich in NADH transferase, myoglobin, ATPase
Many Mitochondria
Primarily use Oxidative Phosphorylation 
Slow & continuous contractions
Referred to as dark or red fibers
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5
Q

Describe Type IIA Myofibers

A

Intermediate staining for oxidative enzymes
Aerobic and anaerobic respiration for ATP
Contract more rapidly than Type I
Resistance to fatigue

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6
Q

Describe Type IIB Myofibers

A 
Light staining for oxidative enzymes
Primarily anaerobic respiration for ATP
Contract more rapidly than Type I or Type IIA
Fatigue quickly
Referred to as white or light fibers
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7
Q

Smooth Muscle Characteristics

A 
Single mononucleated cells
No sarcomeric arrangement
Cells innervated via ANS
Do not respond "all or none"
Cell connected via Gap Junctions
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8
Q

Cardiac Muscle Characteristics

A 
Single mononucleated cells
Centrally positioned nuclei
Branching 
Sarcomeric arrangement 
Gap Junctions (intercalated disks)
Not directly innervated
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9
Q

A muscle is composed of many ______

A

fascicles

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10
Q

A fascicle is a bundle of _____

A

myofibers

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11
Q

A myofiber is bundle of ______

A

Myofibrils

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12
Q

A myofibril is a linear array of ______

A

Sarcomeres

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13
Q

A sarcomere is made up of what two types of filaments?

A 
Thin = actin
Thick = myosin
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14
Q

A muscle is covered by a CT tissue sheet called the ______

A

epimysium (abundance of type I collagen)

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15
Q

A fascicle is covered by a CT sheet called the ______

A

Perimysium

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16
Q

What does the perimysium consist of?

A

Fibroblasts and type I collagen

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17
Q

A myofiber is a muscle cell and is surrounded by a cell membrane called the ________

A

Sarcolemma

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18
Q

The ______ covers the muscle fiber, including the sarcolemma

A

Endomysium

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19
Q

The endomysium consists of:

A

A basal lamina and reticular collagen fibers

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20
Q

The basal lamina is secreted by:

A

Muscle cells

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21
Q

What is the function of the basal lamina?

A

Anchors muscle fibers to each other

Helps distribute the force of contraction

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22
Q

Review the structure of a Sarcomere

A

Slide 31

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23
Q

Review Sliding Filament Theory

A

Slide 33

24
Q

Thick filaments are made up of:

A

Myosin

25
Q

Describe Myosin

A

Dimeric protein with long tails and two head groups

26
Q

Each myosin head group has:

A

Actin binding region
ATP-Binding Region
Light-chain binding region
(Review slide 38 for more detail)

27
Q

Describe the two pairs of light chains on myosin

A

Similar to calmodulin, but have lost ability to bind Calcium
Essential light chains (stability of heads)
Regulatory light chains (stability of myosin II; phosphate binding)

28
Q

Thin filaments are made of:

A

actin

29
Q

Describe F actin

A

Polymer of G actin
Each actin filament consists of 2 polymers in alpha-helix configuration
Plus end inserts on Z-disk

30
Q

Name the two actin-associated molecules

A

Troponin
Tropomyosin
(Review slide 41)

31
Q

What are the three troponin molecules?

A

Troponin I
Troponin C
Troponin T

32
Q

What is the function of Troponin I?

A

Inhibits binding between actin and myosin

33
Q

What is the function of Troponin C?

A

Binds calcium ions

34
Q

What is the function of Troponin T?

A

Binds to tropomyosin

35
Q

What do we call the enlargements of the sarcoplasmic reticulum?

A

Cisternae

36
Q

What do cisternae do?

A

sequester calcium ions

37
Q

What are T-tubules?

A

Extensions of the sarcolemma that extend down into the sarcoplasm
Located at the A-I junction

38
Q

What is the function of T-tubules?

A

Provide electromechanical coupling for myofiber contraction by transferring the AP of the sarcolemma into calcium release from the cisternae

39
Q

AB-Crystallin

A

Heat-shock protein that protects desmin from mechanical stress

40
Q

Dystrophin

A

1 of the proteins that links a-actin/desmin complex to cytoplasmic side of sarcolemma
Anchors actin to sarcolemma
Reinforces sarcolemma during muscle contraction

41
Q

Dystroglycan complex

A

Links dystrophin (intracellular) to laminin-2 (extracellular)

42
Q

a-Actinin

A

Attached thin filaments to the Z line

43
Q

Titin

A

Large fibrous protein
Extends from Z disk to middle of H-band & connects ends of thick filaments to Z-line
Provides myosin w/ elasticity
Centers thick filaments in the sarcomere

44
Q

Desmin Intermediate Filaments

A

Framework of desmin filaments which surrounds the Z line & extends into each sarcomere
Links myofibrils laterally & to sarcolemma

45
Q

Plectin

A

Binds desmin filaments

46
Q

Nebulin

A

Extends from Z disc to end of actin filament

Serves as template to regulate length of actin filaments

47
Q

Muscular Dystrophy

A

X-linked inherited disease, results in progressive degeneration of skeletal muscle
Dystrophin is either absent (Duchenne’s) or abnormal (Becker’s)

48
Q

Satellite Cell attach to ______ before basal lamina is laid down.

A

Myotubes

49
Q

Satellite cells function as:

A

Stem cells

50
Q

Satellite cells can become _____ in times of stress

A

mitotic

C-Met receptor for HGF

51
Q

Satellite cells give rise to:

A

Myogenic precursor cells

- Replace damaged muscle by proliferating, fusing, and differentiating into skeletal muscle fibers

52
Q

Neuromuscular Spindle Components

A 
Extrafusal Fibers
Intrafusal Fibers
Alpha Motor Neurons
Gamma Motor Fibers/Neurons 
Primary and Secondary Afferent Fibers
53
Q

Intrafusal Fibers

A

Nuclear bag region = sensory region
Nuclear bag fibers
Nuclear chain fibers

54
Q

Alpha motor neurons

A

To extrafusal fibers

55
Q

Gamma motor neurons

A

To intrafusal fibers

Whitney - Histology Test 2 (11 decks)

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