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Histology > Muscle Tissue > Flashcards

Muscle Tissue Flashcards

1
Q

What are the components of thin myofilaments?

A

Actin and accessory proteins

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2
Q

What are the components of thick filaments?

A

Myosin 2

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3
Q

What three types of muscle tissue do we have?

A
  1. Smooth muscle
  2. Skeletal muscle (striated)
  3. Cardiac muscle (striated)
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4
Q

Which types of muscle tissue is voluntary and which is not voluntary?

A

Voluntary: Skeletal muscle

Not voluntary: Smooth muscle and cardiac muscle.

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5
Q

What is the main difference between the contractile apparatus in smooth muscle and skeletal muscle?

A

The contractile apparatus in smooth muscle is less regularly organized. The contractile apparatus in skeletal muscle is organized in sarcomeres.

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6
Q

Is the contraction in smooth muscle slow or fast?

A

Slow but durable.

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7
Q

Where are the basal lamina of smooth muscle cells and some of the extracellular components (elastic and reticular fibers) produced?

A

Inside the smooth muscle cell.

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8
Q

How are the smooth muscle cells grouped and organised?

A

Smooth muscle cells are grouped in layers (membranes) or bundles.

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9
Q

What are the junctions between smooth muscle cells called, and what do they allow for?

A

Smooth muscle cells are interconnected by gap junctions and this allows for propagation of stimuli.

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10
Q

Where do you find smooth muscle cells that are grouped in layers?

A

You find smooth muscle cells grouped in layers in the:

  1. Blood vessels
  2. Alimentary tract
  3. Urinary tract (inc. urinary bladder and uterus)
  4. Reproductive tract
  5. Respiratory tract
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11
Q

How are the smooth muscle cells formed?

A

Smooth muscle cells are elongated and have a fusiform shape ( Wide in the middle and reduce in thickness towards the end)

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12
Q

How is the nucleus of smooth muscle cells formed?

A

They are elongated

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13
Q

Where can you find the organelles of smooth muscle cells?

A

The organelles of smooth muscle cells are clustered near the poles of the nucleus.

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14
Q

Why are the organelles of smooth muscle cells clustered near poles of the nucleus?

A

To make space for the contractile apparatus in the cytoplasm.

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15
Q

Are thin or thick myofilaments most numerous in smooth muscle cells?

A

Thin myofilaments (actin) are most numerous in smooth muscle cells.

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16
Q

What attaches the thin myofilaments together and to the cells membrane?

A

Dense bodies containing actin-binding proteins. Dense bodies in smooth muscle cells are analogous to the Z-discs of cardiac and skeletal muscle cells.

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17
Q

Mention 2 types of dense bodies in smooth mucle cells and what their function is.

A

Alpha actinin: Anchors the thin filaments to each other.

Vinculin: Anchors the thin filaments to the cell membrane.

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18
Q

What is a caveola

A

Caveola is flask-shaped invaginations in the cell membrane of any vertebrate cell that is especially involved in endocytosis.

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19
Q

What are the thin myofilaments in smooth muscle cells?

A
  1. Actin
  2. Tropomyosin
  3. Caldesmon
  4. Calponin
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20
Q

What are the thick myofilaments in smooth muscle cells?

A

Myosin 2

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21
Q

What are the steps of smooth muscle contraction?

A
  1. Stimulus
  2. Opening of calcium channels in the cell membrane
  3. Rise of cytoplasmic Ca2+ level
  4. Binding of calcium ions to caldesmon and calponin (increase in ATPase activity of myosin) and to cytoplasmic protein calmodulin
  5. The Ca-calmodulin complex activates myosin light chain kinase.
  6. The kinase phosphorylates myosin light chains
  7. Myosin heads can bind to actin
  8. Myosin heads walk along actin filament - contraction
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22
Q

What are interstitial cells of Cajal?

A

Interstitial cells of Cajal (ICC) are mesenchymal cells located within the muscle layers of the alimentary tract, blood vessels, and ureter that mediate communication between the autonomic nervous system and smooth muscle

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23
Q

What are the interstitial cells of Cajal very numerous in?

A

ICC’s are very numerous in:

  1. Long processes
  2. Nerve terminals
  3. Gap junctions.
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24
Q

What are the functions of ICC’s?

A

The ICC’s are pacemaker cells meaning that they spontaneously generate signals for contraction. They also mediate in the propagation of signals between nerve terminals and working smooth muscle.

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25
Q

What are nonmuscle contractile cells?

A

Nonmuscle contractile cells are cells not characterized as muscle cells but have the capability of contracting due to contractile apparatus similar to that of smooth muscle.

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26
Q

What are 4 nonmuscle contractile cells?

A
  1. Myoepithelial cells
  2. Myofibroblasts (fibrocytes)
  3. Myoid cells
  4. Pericytes
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27
Q

What are the origin of the different non muscle contractile cells?

A
  1. Myoepithelial cells - Epithelial origin
  2. Myofibroblasts (fibrocytes) - Mesenchymal origin
  3. Myoid cells - Mesenchymal origin
  4. Pericytes - Mesenchymal origin
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28
Q

What is function of myoepithelial cells?

A

Myoepithelilal cells helps to push secretion to ducts.

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29
Q

What is the function of myofibroblasts?

A

Myofibroblasts produce collagen fibers and help to close wounds under repair in the skin.

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30
Q

What is the function of myoid cells?

A

Myoid cells help to push the spermatozoa

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31
Q

What is the function of pericytes?

A

Pericytes influence capillary lumen

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32
Q

Where does the myoepithelial cells occur?

A

Myoepithelial cells occur in some glands.

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33
Q

Where do the Myofibroblasts occur?

A

Myofibroblasts (fibrocytes) occur in the skin and some organs.

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34
Q

Where do the Myoid cells occur?

A

Myoid cells occur in the testis

35
Q

Where do the pericytes occur?

A

Pericytes occur in the capillaries

36
Q

What is a sarcomere?

A

A sarcomere is the regularly organized contractile apparatus in skeletal and cardiac muscle.

37
Q

Does skeletal muscle contract fast or slow?

A

Skeletal muscle contracts fast but is prone to fatigue.

38
Q

What is epimysium?

A

Epimysium is a sheath of fibrous tissue that surrounds a muscle.

39
Q

What is perimysium?

A

Perimysium is a sheath of connective tissue that surrounds bundles of muscle fibers.

40
Q

What is endomysium?

A

Endomysium fills spaces between muscle fibers.

41
Q

What other than cells does connective tissue investments contain?

A

Blood vessels and nerve fibers

42
Q

What are skeletal muscle fibers?

A

Skeletal muscle fibers are multinucleated syncytium formed by the fusion of numerous progenitor cells (myoblasts)

43
Q

What is the cell membrane + the basal lamina of skeletal muscle cells called?

A

Sarcolemma.

44
Q

Where are the contractile apparatus located in skeletal muscle cells?

A

The contractile apparatus is located in a central region in the skeletal muscle cell.

45
Q

What are the main organelles in skeletal muscle cells?

A

The main organelles of skeletal muscle cells are RER and Golgi.

46
Q

What occupies the spaces between myofibrils?

A

Mitochondria, T tubules and sarcoplasmic reticulum.

  • Glycogen and myoglobin are also abundant.
47
Q

What is the Z line of sarcomeres built of?

A

Alpha actinin interconnects and ends of thin myofilaments.

48
Q

What is the M line of sarcomeres built of?

A

M line is built of myomesin. M line forms lateral bridges, interconnecting thick myofilaments.

49
Q

What is the role of nebulin filaments?

A

Nebulin filaments stabilize the thin myofilaments in sarcomeres.

50
Q

What is the role of titin filaments?

A

Titin prevents excessive stretching of the sarcomere.

51
Q

What is the role of tropomodulin?

A

Tropomodulin prevents elongation of thin myofilaments

52
Q

What is the role of dystrophin?

A

Dystrophin molecules anchor the peripheral actin filaments to the cell membrane.

53
Q

What causes a severe myodegenerative disease called Duchenne muscular dystrophy?

A

Mutation of the dystrophin gene.

54
Q

What is the role of transverse intermediate filaments called desmin in myofibrils?

A

Desmin holds the sarcomeres at the same level by anchoring the z lines to the cell membrane.

55
Q

What are the steps of skeletal muscle contraction?

A
  1. Rise of cytoplasmic Ca2+ level (intracellular signal)
  2. Ca binds to troponin C
  3. Troponins I and T pull tropomyosin away from actin, unmasking the myosin-binding sites on thin myofilament.
  4. Myosin heads bind to actin
  5. Using energy from ATP, myosin heads walk along thin myofilament
  6. Sarcomeres contract.
56
Q

Does muscle fibers get a stimulus from the same nerve terminal?

A

No, the muscle fibers get the stimulus from a separate nerve terminal.

57
Q

Where does the T tubules from invaginations?

A

The T tubules forms invaginations of the cell membrane surrounding myofibrils at the level of I/A border.

58
Q

What is the muscular triad?

A

T tubule + 2 terminal cisternae of SR.

59
Q

What are the steps from excitation to the intracellular signal of skeletal muscle cells?

A
  1. Transmission of stimulus at the motor end plate.
  2. Propagation of stimulus along the cell membrane and T tubule membranes.
  3. Conformational change of voltage-sensitive protein in T tubule membrane
  4. Mechanical opening of the adjacent calcium channels in the SR membrane.
  5. Rise of the Ca level in the cytoplasm (i.e. also between myofilaments)
60
Q

How is the muscle fibers anchored to the collagen fibers at the tendon?

A

Via a protein called integrins.

61
Q

What are the three types of skeletal muscle fibers?

A

Red (slow-twitch, type 1)

White (fast-twitch, type 8)

Intermediate ( type IIA)

62
Q

What are the characteristics of white fibers?

A
  1. Larger in diameter.
  2. Less myoglobin.
  3. Fewer mitochondria
  4. Narrower z lines
  5. Very fast contraction
  6. Rapid fatigue.
63
Q

What are the characteristics of red fibers?

A
  1. Smaller in diameter.
  2. More myoglobin
  3. More mitochondria
  4. Broader Z lines
  5. Slower contraction
  6. More endurable.
64
Q

What are satellite cells?

A

Satellite cells are skeletal muscle stem cells located on the surface of skeletal muscle fibers under the basal lamina.

65
Q

What are the function and roles of satellite cells?

A

Satellite cells can divide and form new fibers or incorporate into existing fibers.

  • They are also responsible for hypertrophy and remodeling and regeneration of skeletal muscles.
66
Q

How is the contractile apparatus organized in cardiac muscle cells?

A

The contractile apparatus is organized into sarcomeres in cardiac muscle.

67
Q

How is cardiac muscle built up?

A

Cardiac built up by separate cells.

68
Q

What is meant by saying that cardiac muscle has a conduction system?

A

The muscle responds to its own self-excitable cells.

  • Cardiac muscles undergo permanent rythmic spatial contraction.
69
Q

Why are the cardiomyocytes branched and forms a three-dimensional network?

A

To be able to perform spatial contractions.

70
Q

What is located between cardiomyocytes?

A

Numerous capillary vessels are located between cardiomyocytes.

71
Q

How many nuclei do cardiomyocytes have and where are they located?

A

Cardiomyocytes have 1-2 nuclei and they are located centrally in the cell.

72
Q

Where are the organelles of cardiomyocytes located?

A

The organelles of cardiomyocytes are located around the nucleus.

73
Q

Do cardiomyocytes have mitochondria?

A

Yes, cardiomyocytes are very numerous in mitochondria.

74
Q

What is an early indicator of myocardial infarction?

A

Thin filaments have specific types of troponin, different from that in skeletal muscle. Detection of these troponins in blood or tissue fluids may be an early indication of a heart attack.

75
Q

How does the T tubules and sarcoplasmic reticulum in cardiomyocytes differ from that in skeletal muscle?

A
  1. Wider, glycocalyx-linked T tubules at the levels of Z-lines.
  2. Smaller terminal cisternae of SR.
  3. Diads instead of triads.
  4. Voltage gated calcium channels in T tubules, initial increase in Ca level opens other Ca-gated calcium channels in SR (amplification)
76
Q

How are cardiac muscle cells interconnected end to end?

A

The cardiomyocytes are interconnected by multiple junctional complexes, intercalated discs, containing desmosomes, adhesion junctions, and gap junctions.

77
Q

What is atrial cells?

A

Atrial cells are the cardiomyocytes located in the walls of the atria of the heart.

78
Q

How do atrial cells differ from ventricular cells?

A
  1. Smaller
  2. No T tubules
  3. Some of them produce a hormone (atrial natriuretic peptide)
79
Q

What are the characteristics of cells of the conduction system?

A
  1. No T tubules
  2. Numerous gap junctions
  3. Poor contractile apparatus.
80
Q

What is the sinoatrial node?

A

The sinoatrial node (SA node) is a specialized myocardial structure that initiates the electrical impulses to stimulate contraction.

81
Q

What is the atrioventricular node?

A

The atrioventricular node or AV node is a part of the electrical conduction system of the heart that coordinates the top of the heart. It electrically connects the atria and ventricles.

  • Spontaneous, rhythmic depolarization.
82
Q

What is bundles of His and Purkinje fibers?

A

Bundles of cells connected by gap junctions with each other and working cardiomyocytes - propagation of stimuli.

83
Q

What happens with the cardiac muscle cells after damage to them?

A

They can not regenerate and are replaced by fibrous connective tissue.

84
Q

Where are cardiac stem cells located?

A

Small cells located between cardiomyocytes

  • They do not function in the heart.

Histology (14 decks)

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