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Histology > Muscle Tissue > Flashcards

Muscle Tissue Flashcards

1
Q

Layers of skeletal muscle?

A
  • epimysium: external sheath of dense irregular connective tissue w/ septa that extend inwards w/ nerves/vessels/lymphs
  • perimysium: thin connective tissue around each bundle of mm fibers (fascicle/functional unit)
  • endomysium: thin, delicate layer of reticular fibers and fibroblasts arr external lamina of each mm fiber; hold capillaries for O2
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2
Q

Where are mm layers cont w/ tendon connective tissue?

A

Myotendinous junctions

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3
Q

Describe features of myofibrils

A
  • dark bands = A bands

- light bands = I bands, bisected by Z disc

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4
Q

Boundaries of sarcomere?

A

Z disc to Z disc

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5
Q

Composition and location of thick/thin myofilaments?

A
  • thick = myosin @ A-band

- thin = F-actin

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6
Q

What are the 2 regulatory proteins of thin filaments?

A
  1. Tropomyosin, located in groove b/w 2 twisted actin strands
  2. Troponin; complex of TnT (binds tropomyosin), TnC (binds Ca2+), and TnI (regulates actin-myosin sys)
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7
Q

Types of collagen in skeletal mm tissue?

A

Types 1 and 3 (reticulin)

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8
Q

What protein anchors actin filaments to Z disc?

A

alpha actinin binding protien

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9
Q

Purpose of titin?

A
  • supports thick myofilaments

- connects them to Z disk

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10
Q

Functions of nebulin? (2)

A
  • binds each thin myofilament laterally
  • anchors them to alpha actinin
  • specifies length of actin polymers during myogenesis
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11
Q

What is not found in H zone w/i A band?

A

Thin filaments

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12
Q

Location and composition of M line?

A
  • bisects H zone

- holds myomesin and creatine kinase

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13
Q

Function of myomesin?

A
  • binds myosin to hold it in place
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14
Q

Function of creatine kinase?

A
  • transfers phos groups from phosphocreatine to ADP –> ATP production
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15
Q

Function of transverse (T) tubules?

A
  • in sarcoplasmic reticulum
  • helps trigger release of Ca2+ from SR and contraction
  • invaginations of PM that insert onto sarcoplasm to encircle each myofibril
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16
Q

Location and function of terminal cisternae?

A
  • adjacent to each T-tubule
  • T-tubule + 2 terminal cisternae = triad
  • triad –> depolarization of sarcolemma in T-tubule –> Ca2+ release
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17
Q

When is contraction induced? (2)

A
  • AP arrives @ neuromuscular junction (NMJ or motor end plate – MEP)
  • transmitted along T-tubules to terminal cisternae of SR –> Ca2+ release
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18
Q

Why can myosin not bind actin in the resting state?

A

Blocked by troponin-tropomyosin complex

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19
Q

What is a motor unit?

A
  • 1 axon and all the mm fibers in contact w/ its branches
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20
Q

Mechanism of myasthenia gravis? (4)

A
  • autoimmune disorder
  • Ab’s against proteins of ACh receptors
  • receptors can’t be activated by ACh
  • intermittent skeletal mm weakness
  • extraocular mm of eyes are first affected
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21
Q

Motion of titin molec’s during contraction?

A

Compressed

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22
Q

Function and description of muscle spindles? (4)

A
  • stretch detectors
  • concentric layers of flattened cells w/ interstitial fluid and intrafusal fibers
  • penetrated by sensory axons
  • monitor changes in length (distension) of surr (extrafusal) mm fibers
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23
Q

Function and description of Golgi tendon organs? (3)

A
  • enclose sensory axons that penetrate collagen bundles @ myotendinous junction (MTJ)
  • detect changes in tension w/i tendons
  • inhibit motor nn activity in xs tension
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24
Q

Mechanism of Duchenne musc dystrophy? (3)

A
  • mutations in dystrophin gene
  • defective linkages b/w cytoskeleton and ECM
  • mm contractions disrupt linkages –> mm fiber atrophy
25
Q

3 types of skeletal mm fiber?

A
  1. Slow oxidative: slow contractions over long pd’s w/o fatigue; many mitochond and capillaries (dark red)
  2. Fast glycolytic: rapid, short-term contraction; few mitochond or capillaries (white)
  3. Fast oxidative-glycolytic: intermediates
26
Q

How many nuclei in each cardiac mm cell?

A

1

27
Q

Describe intercalated discs (3)

A
  • interfaces b/w adjacent cells
  • transverse regions contain desmosomes and fascia adherens junctions
  • longitudinal regions have gap junctions for ionic cont.
28
Q

Major fuel of heart?

A

Fatty acids

29
Q

Do terminal cisterns and T-tubules form dyads or triads in heart mm?

A

Dyads

30
Q

Function of atrial natriuretic factor (ANF) peptide hormone?

A
  • released in secretory granules from heart

- acts on target cells in kidney to affect Na+ secretion and H2O balance

31
Q

Major features of smooth mm cells? (4)

A
  • tapering cells w/ many gap junction
  • 1 elongated nucleus
  • lack T-tubules
  • caveolae = plasmalemma invaginations
32
Q

What proteins produce contraction in smooth mm fibers?

A
  • calmodulin

- Ca2+ sensitive myosin light chain kinase (MLCK)

33
Q

What part of skeletal mm are dense bodies structurally similar to?

A

Z discs

34
Q

What else do smooth mm do besides contraction?

A
  • produce collagen, elastin, and proteoglycans

- confer major influence on ECM

35
Q

What are lelomyomas? (3)

A
  • benign tumors that dvp from smooth mm fibers
  • most often found in wall of uterus (known as fibroids)
  • painful pressure and bleeding
36
Q

Regenerating tools of each muscle type? (3)

A
  • satellite cells for skeletal mm
  • fibroblasts for cardiac mm –> cardiac scars
  • smooth mm cells replace damaged tissue for smooth mm
37
Q

T/F: skeletal mm fibers are held together by cell junctions

A

False, they are bound by connective tissue

38
Q

What holds together fascicles?

A

Perimysium

39
Q

What ensheaths entire skeletal mm?

A

Epimysium (also carries major vasc/nn supply)

40
Q

Position of nuclei in skeletal mm cells?

A

Peripheral placement

41
Q

What protein masks myosin-binding sites on F-actin in resting mm?

A

Tropomyosin

42
Q

What protein changes shape in presence of Ca2+ and pulls tropomyosin away from actin?

A

Troponin

43
Q

What is A band full of?

A

Thick filaments

44
Q

What is I band made of?

A

Thin filaments

45
Q

Where is H band?

A
  • middle of A band, thick filaments only
46
Q

Purpose of M line?

A

Anchors thick filaments

47
Q

What band does not change length during contraction?

A

A band, b/c myofilaments don’t shorten

48
Q

Relationship b/w motor unit and coarseness of movement?

A

Fewer mm fibers in a unit = finer movement

49
Q

What type of collagen fiber makes up most tendons?

A

Type 1 collagen

50
Q

IM filaments found in smooth mm? (2)

A
  • desmin

- vimentin

51
Q

How are smooth mm cells connected?

A

Gap junctions

52
Q

Importance of side-polar thick filaments? (3)

A
  • found in smooth mm
  • myosin filaments aligned in opposite directions on either side of filament
  • no central bare zone like in bipolar thick filaments
53
Q

During voluntary contraction of skeletal mm, the sarcomere:

A

Gets shorter

54
Q

Basal lamina of a mm fiber is part of which structure?

A

Endomysium

55
Q

What characteristic is unique to cardiac mm?

A

Often branched

56
Q

What feature typifies T-tubules?

A

Carry depolarization to mm fiber interior

57
Q

T/F: Smooth muscle cells of the multiunit type are connected by GAP junctions and can contract spontaneously

A

False

58
Q

T/F: Individual skeletal muscle fibres are surrounded by perimysium, which is a delicate network of reticular fibres

A

False

59
Q

T/F: The H-band of the sarcomere corresponds to the part in which actin and myosin filaments overlap

A

False

Histology (7 decks)

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