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HISTO - Exam 2 > Muscle > Flashcards

Muscle Flashcards

1
Q

Covering over an entire muscle.

A

epimysium

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2
Q

Covering over a muscle fascicle.

A

perimysium

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3
Q

Covering over an individual muscle fiber.

A

endomysium

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4
Q

What makes up the endomysium?

A

Basal lamina and reticular fibers

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5
Q

What layers are satellite cells found between?

A

Sarcolemma and basal lamina

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6
Q

What are satellite cells? What is their function?

A

Stem cells, proliferate after trauma to form myoblasts

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7
Q

State the muscle structure hierarchy (from big to small).

A

Muscle (covered by epimysium) > Fascicle (covered by perimysium) > muscle fiber/cell (covered in endomysium) > myofibers > myofilaments

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8
Q

Explain how the A-band, I-band, and Z-line stain with H&E.

A

A-band: dark red, I-band: light red / pink, Z-line: may be seen as dark line that bisects I-band.

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9
Q

Explain the train complex. What muscle type is it common in?

A

T-tuble flanked by sarcoplasmic reticulum on both sides. Most common in skeletal muscle.

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10
Q

What structure do t-tubules align with in muscle cell sarcomeres?

A

A-I band junction

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11
Q

Define teloglia.

A

Axon and Schwann cell at motor end plate. (The basal lamina fuses with the muscle fiber here.)

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12
Q

Define a motor unit.

A

An nerve and the muscles it innervates.

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13
Q

How does botulism toxin block myoneural junction signaling?

A

Blocks Ach release at PRESYNAPTIC membrane.

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14
Q

How does curare block myoneural junction signaling?

A

Blocks association between Ach and its receptor.

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15
Q

How does myasthenia gravis autoantibody block myoneural junction signaling?

A

Blocks association between Ach and its receptor.

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16
Q

Role of the t-tuble.

A

Conduct depolarizing ions (Na+) into the cell quickly uniformly.

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17
Q

Ion released from sarcoplasmic reticulum.

A

Ca2+

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18
Q

What muscle fiber molecule binds Ca2+?

A

troponin

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19
Q

What are the distinguishing characteristics of red fibers?

A

Also known at type 1, slow twitch fibers

  • High myoglobin
  • Numerous mitochondria
  • Fatigue reistant
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20
Q

What are the distinguishing characteristics of white fibers?

A

Also known as type 2, fast twitch fibers

  • Lower myoglobin
  • Lower mitochondria content
  • More stored glycogen
  • Higher myosin-ATPase activity
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21
Q

What are the distinguishing characteristics of intermediate fibers?

A

Characteristics between red and white fibers.

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22
Q

What is the relationship between neuron type and red/white fiber identity?

A

Innervation determines fiber type. Fibers can be converted by removing innervation and replacing with neuron that innervation opposite fiber type.

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23
Q

What is the function of a muscle spindle?

A

Sense changes in muscle length (stretch receptor).

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24
Q

What are the two types of intrafusal fibers?

A

Nuclear bag and nuclear chain

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25
Q

Who is the best super hero?

A

HistoMan

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26
Q

What type of sensory nerve fibers wind around intrafusal fibers?

A

Annulospiral

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27
Q

What factors stimulate proliferation of satellite cells following muscle injury?

A

MyoD (transcription factor) and HGF (hepatocyte growth factor)

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28
Q

Explain rigor mortis.

A

Death > SR membrane becomes permeable > Ca2+ escape > myosin-actin binding > No ATP to break cross-bridge or allow SERCA to pump Ca2+ back into SR > cross bridge remains until decomposition.

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29
Q

What causes muscle atrophy? Hypertrophy?

A

Atrophy: decrease in muscle fiber size (fewer myofibrils) Hypertrophy: increase in muscle fiber size (more myofibrils)

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30
Q

Where did our microsoft fee go?

A

Turek 2019 Presidential Campaign: “It’s a wonderful time to be alive.”

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31
Q

List the types of myofilaments and state whether each is thick or thin.

A

Troponin - thin
Tropomyosin- thin
Actin - thin
Myosin - thick

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32
Q

What makes up the A band?

A

Thick filaments (only place where they are found)

33
Q

What makes up the I band?

A

Thin filaments

34
Q

Elastic protein that connects myosin to Z-disk

A

titin

35
Q

Inelastic protein that run parallel to actin

A

nebulin

36
Q

myosin binding protein, holds myosin filaments in register at M-line

A

myomesin

37
Q

Myosin binding protein with similar function to myomesin

A

C-protein

38
Q

Bundles actin filaments into parallel arrays and anchors them to Z-disk

A

alpha-actinin

39
Q

Intermediate filaments that binds myofibirls to each other. Interacts with myofibrils at Z-line/disk

A

Desmin

40
Q

Holds desmin together

A

Plectin

41
Q

Actin binding protein, links cytoskeleton (actin) with ECM

A

Dystrophin

42
Q

H-band

A

contains myosin (no heads) and creatine kinase

43
Q

Role of creatine kinase?

A

ADP + phosphocreatine ==creatine kinase==> ATP + creatine

44
Q

Attachement region for thin filaments, contains alpha-actinin

A

Z-disk

45
Q

What regulates polymerization of actin?

A

Thymosin beta4 and profilin (cofilin, severin, gelsolin, villin CapZ, and gCAP39 also listed)

46
Q

3 functionally relevant troponin peptides

A

Tn-T
Tn-I
Tn-C

47
Q

Role of Tn-C peptide

A

Binds Ca2+ and releases TnI-tropomyosin inhibition of actin myosin binding.

48
Q

Role of Tn-I peptide

A

Inhibits myosin head, actin binding (cross bridge formation)

49
Q

Tn-T

A

binds to Tn complex of tropomyosin

50
Q

Role of sarcoglycans

A

Maintain association between sacrolemma and ECM

51
Q

Length of myosin thin filament.

A

15nm

52
Q

What molecules make up a single myosin thick filament?

A

2 identical heavy chains and 4 lights chains (a pair associated with each heavy chain)

53
Q

List the steps muscle contraction with regard to cross-bridge formation. (Start with ATP hydrolysis. Since this is a repeating cycle, their is no true start.)

A

1) ATP Hydrolyzed causing myosin head to be “cocked”
2) Myosin head binds actin
3) Pi released, ADP released
4) Head “snaps” back (power-stroke) pulling actin towards M-line (I-band shrinks)

54
Q

How are cardiac muscle cell nuclei different from muscle cell.

A

One/cell, more round, more centrally located

55
Q

What joins cardiac cells together?

A

intercalated disks

56
Q

What are the parts of an intercalated disk?

A

lateral portion

transverse portion

57
Q

What is present in the lateral portion of an intercalated disk?

A

gap junctions

58
Q

What is present in the transverse portion of an intercalated disk?

A

fasciae adherens and macula adherens

59
Q

Diad

A

T-tuble, sarcoplasmic reticulum unit common in cardiac cells

60
Q

Where do T-tubules meet cardiac myofibrils

A

Z-disk

61
Q

Role of satellite cells in cardiac muscle.

A

None. Satellite cells not present here. Cardiac muscle cannot regenerate and forms fibrous connective tissue instead.

62
Q

What is the functional physiological effect of phopholamban?

A

Decrease rate and contractility of heart

63
Q

What is the molecular function of phospholamban?

A

Inhibit SR Ca2+ ATPase (SERCA)

64
Q

What activates/deactivates phospholamban?

A

phosphorylation of phospholamban attenuates its inhibitory ability

65
Q

What is the role of SR Ca2+ ATPase (SERCA)

A

Actively pump Ca2+ back into SR using ATP hydrolysis to drive active transport

66
Q

What hormone controls phospholamban?

A

Thyroid hormone, reduces phospholamban function (leads to its phosphorylation)

67
Q

What is the effect of MI on cariocyte staining?

A

Cells have eosinophilic staining and pyknotic nuclei after 24 hours, Inflammatory cells infiltrate tissue after 3 days

68
Q

How long are cardiac muscle cells?

A

100-150 um

69
Q

How long are smooth muscle cells?

A

20 um (may be greater than 500 um in gestational uterus, DAMN that’s some serious stretching)

70
Q

Alpha-actin containing areas that serve as the insertion points for actin/myosin filaments in smooth muscle?

A

Dense bodies

71
Q

What is the arrangement of smooth muscle cells?

A

staggered

72
Q

What is the embryonic origin of single smooth muscle cells?

A

Ectoderm (ex. salivary, lacrimal, sweat, mammary glands)

73
Q

What is the embryonic origin of smooth muscle located in respiratory, circulatory, digestive, and reproductive tracts?

A

Mesoderm

74
Q

What is the functional equivalent of smooth muscle dense bodies in skeletal muscle?

A

Z-disk

75
Q

Where is troponin located in smooth muscle cells?

A

Smooth muscle cells don’t have troponin!

76
Q

What filaments are present in smooth muscle cells?

A

Actin and tropomyosin - thin
Desmin and vimentin - intermediate (serve as links in cytoskeletal network between dense bodies)
Myosin - thick

77
Q

Explain the pathway that leads to smooth muscle cell contraction.

A

Ca2+ released into cytoplasm > Ca2+ - calmodulin complex forms > Ca2+-calmodulin complex activates myosin light chain kinase > Myosin light chain kinase phosphorylates myosin > myosin unfolds and forms filaments > myosin filaments interact with actin > contraction

78
Q

What is the significance of estrogen and progesterone with regard to smooth muscle contraction?

A

Estrogen increases cAMP levels, Progesterone decreases cAMP. cAMP may also activate myosin light chain kinase

HISTO - Exam 2 (6 decks)

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