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MSK phys > muscle contraction - seidler > Flashcards

muscle contraction - seidler Flashcards

1
Q

GSD V/ McArdle disease DM, s/s

A
  • autosomal recessive disorder
  • deficiency in muscle glycogen phosphorylase, rate limiting enzyme of glycogen degradation cleaving glucose residues from glycogen for release as glucose 1-phosphate
  • suffer from fatigue, severe muscle cramping, myoglobinuria
  • tolerate by reducing strenuous physical activity
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2
Q

mutations in liver phosphorylase causes

A

Hers disesae (GSD VI)

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3
Q

mutations in muscle phosphorylase causes

A

McArdle syndrome (GSD V)

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4
Q

Duchenne muscular dystrophy (DMD)

A

X-linked recessive disorder
1 in 3500 incidence
- progressive muscle wasting, wheel chair by age 12, respiratory failure death within 10 years
-

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5
Q

dystrophin

A

rod-like protein connecting cytoskeleton to basal lamina and stabilizing membranes and participating in calcium handling
partially absent in BMD, in frame mutation
completely absent in DMD, out of frame deletion

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6
Q

milder form of DMD with later onset

A

Becker muscular dystrophy (BMD)

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7
Q

cTn-I

A

cardiac muscle isoform of Tn-I, inhibitory, subunit of troponin
serum levels increase after myocardial infarction!

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8
Q

sTn-I

A

has two forms

skeletal muscle isoform of Tn-I, inhibitory, subunit of troponin

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9
Q

troponin subunits and importance

A

trimeric protein complex
- Tn-T tropomysin binding subunit; positions complex on filament
- Tn-C Calcium binding subunit; binds Ca2+ and relieves inhibition
- Tn-I inhibitory subunit; binds actin, inhibts myosin binding
Ca2+ binding changes proteins conformation, change transmitted to tropomyosin, allowing myosin to bind to actin filaments, resulting in muscle contraction

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10
Q

area of just thin filaments/ actin

A

I band

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11
Q

area of just thick filaments/ myosin

A

H zone

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12
Q

extends entire length of thick filaments

A

A band

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13
Q

disk off of which myosin chains coming ooff

A

M disk

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14
Q

disk off of which thin filaments coming off

A

Z disk

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15
Q

myosin head and tail

A

head region can hydrolyze ATP

self assembles at tails - bipolar assembly

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16
Q

myosin is made up of

A

6 polypeptide chains (2 heavy chains; 4 light chains)
rod domain (helical)
two globular heads

17
Q

myosin heads are at ?? degree rotational symmetry

and surrounding thin filaments are at ??

A

myosin 30 degrees
thin filaments 60 degrees apart
so 6 thin filaments surrounding each actin 360 degrees circle

18
Q

in myosin structure, a and d are always positioned next to each other leading to

A

strong hydrophobic intreactions -> high structural integrity

19
Q

binding of ATP to myosin allows it to??

messed in what process??

A
  • allows it to disengage thin filament

whats happening in rigormortis! no o2, atp

20
Q

how can a point mutation in myosin lead to a DOMINANT NEGATIVE mutation?

A
  • one normal protein still being pumped out however A to D and D to A lining up of myosin messe dup leading to dominant illness
  • so one bad copy messed you up
21
Q

each G acti nmonomer interacts with

A

4 neighbors

22
Q

mature actin filament contains

A

ADP bound to monomeric G-actin units

23
Q

caps the minus end (not at Z-disc) of thin filament preventing further polymerization

A

tropomodulin

24
Q

caps at plus end of thin filament

A

CapZ (or b-actinin, a heterodimer) associates with a-actinin

25
Q

“ruler” and template for actin polymerization

A

nebulin

26
Q

length of actin

A

1 mm ABSOLUTE

180 repeats of 35 aa residues

27
Q

monomeric form of thin filament?? once polymerize??

A

G actin monomer

F actin polymerized

28
Q

at Z disc, what arranges actin in hexagonal bundle around myosin?

A

a-actinin!

29
Q

rope-ish protein tying z disc and thus myofibrils to one another, turns sarcomeres into “rib-like” costameres

A

desmin

30
Q

“ruler” for sarcomeres

A

titin

31
Q

titin is involve din

A 
muscle ruler
- sarcomere organization
balances forces across sarcomere
passive elasticity (after contraction, sarcomere needs to get back to rest, does it through titin)
muscle signaling
32
Q

how does hypocalcemia lead to tetany when Ca+ is involved in muscle ocntraction?

A

Ca++ automatic inhibitor of VG Na+ channels

  • when Ca++ low, Na+ channel inhibition removed
  • mkaes it more responsive leading to spontaneous firing, get AP and muscle contractions
33
Q

mechanically inhibits ryanadine receptor; changes conformation and releases inhibition upon depolarization of cell

A

dihydropyridine receptor

34
Q

molecular events leading to smooth muscle contraction

A

Ca+ binds to calmodulin
Ca++ - calmodulin complex binds to myosin light-chain kinase and both phosphorylate myosin with nonphosphorylated light chain to activate it

35
Q

chanes active site of muscle glycogen phosphorylase b to increase activity of enzyme leading to G6P, ATP formation

A

binding of AMP

phosphorlation by Ca++-calmodulin complex

MSK phys (7 decks)

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