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825 > Muscle Architecture > Flashcards

Muscle Architecture Flashcards

1
Q

Orientation of Muscles

A

epimysium -> perimysium -> endomysium -> sarcolemma -> sarcoplasmic reticulum

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2
Q

Epimysium

A

surrounds entire muscle; also known as fascia

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3
Q

Perimysium

A

surrounds fasciculi

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4
Q

Endomysium

A

surrounds myocytes (mus cells/mus fibers)

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5
Q

Sarcolema

A

muscle cell membrane; underlies the endomysium

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6
Q

Transverse (T-) Tubules

A

invaginations of sarcolemma
Transmit action potential into interior mus cell
closely apposed to SR

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7
Q

SR

A

membranous sac underlying the sarcolemma
responsible for Ca+ storage (release and uptake)
integral to mus contraction

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8
Q

Terminal Cisternae

A

bulbous enlargements of SR

store and release Ca

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9
Q

Sarcolemma

A

mus cell membrane;

contains sarcoplasm, cellular proteins, organelles, and myofibrils

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10
Q

Myofibrils

A

divided into individual contractile units (myosin and actin)

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11
Q

Thick Filaments

A

myosin

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12
Q

think filaments

A

actin

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13
Q

location of troponin and tropomyosin

A

actin filament

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14
Q

Zone of Sarcomere

A

from Z-disc to Z-disc

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15
Q

M Line

A

myofibril

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16
Q

H Zone

A

contains just myosin

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17
Q

I Band

A

contains just actin

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18
Q

Zone of Overlap

A

contains both myosin and actin

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19
Q

A Band

A

2 overlaps and H zone

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20
Q

Titin/Connectin

A

molecular blueprint
molecular spring
contribution to signal transduction

21
Q

How is titin a molecular blueprint?

A

specifies and coordinates assembly of structural, regulatory and contractile proteins

22
Q

How is titin a molecular spring?

A

links z-disk to M band
maintains relative position of actin and myosin
contributes ot mus extensibility and passive force development

23
Q

Nebulin

A

molecular ruler

24
Q

how is nebulin a molecular ruler?

A

incorporated into and co-extensive with actin
extens form z-disk to end of actin myofilament
precisely regulates actin length

25
Q

Obscurin

A

intimately surrounds sarcomere, primarily at Z-disk and M-band regions
coordinates assembly and organization of SR with myofilament

26
Q

Myosin Chains

A

2 heavy and 2 light polypeptides

27
Q

2 heavy myosin chains

A

light meromyosin

heavy meromyosin

28
Q

What does the light meromyosin do?

A

intertwine in double helix formation to form molecular backbone

29
Q

what does the heavy meromyosin do?

A

project outward to form neck (S2) and globular head (S1)

30
Q

what are the two light chain myosin polypeptides

A

1 essential and 1 regulatory chain for each S1/S2 complex

isoforms fine tune contraction velocity

31
Q

Actin

A

thin
double helix
contains mysoin binding site

32
Q

Tropomyosin

A

resides in groove along length of actin protein

33
Q

what is the purpose of tropomyosin in the absence of Ca+?

A

blocks the myosin binding site

34
Q

Troponin

A 
spaced at regular intervals along length of actin protein
3 subunits (Ti, Tc, Tt)
35
Q

what does troponin do in resting state

A

regulates position of tropomyosin relative to myosin binding site

36
Q

What is the sequence of events for muscle contraction

A

1) action potential propogated along sarcolemma and into T-Tubes
2) Stim release of Ca+ from SR
3) Ca+ binds to Tc - conformation change that pulls tropomyosin away from myosin binding site
4*) hydrolysis of ATP cocks myosin head
5) cocked head binds to action and CONTRACTION OCCURS
6) hydrolysis of ATP detaches myosin head from actin
7) With action potential and thus Ca+ present, cycle keeps on
8) No AP and No Ca+ –> toponin and tropomyosin return and block binding site

37
Q

Slow Twitch Fibers

A

low myosin-ATPase activity associates with lower max contraction and longer time to peak tension

38
Q

Fast Twitch Fibers

A

high myosin-ATPase activity associates with higher max contraction and shorter time to peak tension

39
Q

Type I Fibers

A

slow oxidative

40
Q

Type IIa Fibers

A

fast oxidative-glycolytic

41
Q

Type IIb (or IIx) Fibers

A

fast glycolytic

42
Q

Myoplasticity

A

changes in use and environment can generate alterations in structural and enzymatic protein content

43
Q

what predomenately changes fibers according to myoplasticity?

A

gene expression

Levels: structure, type, metabolism, energy storage, cap den, fxn

44
Q

What causes myoplastic adaptations in endurance training?

A

delayed onset of metabolic acidosis
increased fatigue resistance
increased O2 consumption

45
Q

What are the adaptations in endurance training?

A
  • increased oxidative capacity
  • increased mitochondrial density
  • increased expression of type I
  • decreased expression type IIa (takes years)
  • decreased expression type IIb (takes days)
46
Q

What causes myoplasitc adaptations in resistance training?

A

increase contractibility
improved elasticity
improved neuromotor recruitment

47
Q

What are the adaptations in resistance training?

A
  • increased CSA in all fibers
  • increased nuclei/cell
  • decreased mitochondria density
  • decreased type I
  • decreased type IIb
  • increased type IIa
  • little cap change
48
Q

DMD

A

dystrophin ~5% of cytoskeletal membrane
X-linked recessive
inability to produce dystrophin

49
Q

DMD intervention

A

emphasis on mobility
develop large mus groups and improve strength and increase endurance
avoid joint contractures - rom, stretching, braces
strengthen - resistance, pool

825 (5 decks)

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