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phys > exam 2: skeletal muscle > Flashcards

exam 2: skeletal muscle Flashcards

1
Q

the dark band

A

a-band
thick and thin

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2
Q

light band

A

I-band
only thin

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3
Q

functional unit of cardiac and skeletal muscle

A

sarcomere

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4
Q

when the sarcomere shortens, what moves and what stays

A

I-band shrinks during contractions (H-zone)
and
A-band remains the same

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5
Q

alternating A-bands and I-bands create the _________ appearance in skeletal and cardiac muscle

A

striated appearance

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6
Q

entire length of thick filament

A

a-band (dark)

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7
Q

includes only the thin filament

A

I-band (light)

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8
Q

only thick filament

A

H-zone

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9
Q

thin filaments anchored here

A

z-line

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10
Q

link the central regions of thick filaments

A

m-line

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11
Q

during contraction what decreases:

A

H-zone and I-band

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12
Q

why doesnt a-band change in size

A

because its the same length as the thick filament

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13
Q

thin filaments are composed of____
, ______, and _____

A

actin, tropomyosin, and troponin

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14
Q

(with G-actin molecules, the active site which bind myosin)

A

actin

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15
Q

(which binds actin, tropomyosin and calcium)

A

troponin

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16
Q

covers up myosin binding site of actin

A

tropomyosin

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17
Q

troponin has 3 globular proteins:

A

T, C and I

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18
Q

_____(thick) filaments has multiple cross-bridges where the “heads” can bind to the

A

myosin

g-actin molecule

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19
Q

myosin also functions as the

A

ATPase enzyme

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20
Q

this connects thin filaments to glycoproteins in sarcolemma

A

dystrophin protein

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21
Q

provides scaffolding for sarcomeres

A

dysotrophin protein

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22
Q

muscular dystrophies:

A
  1. duchenne (x-linked)
  2. beckers (milder phenotype)
  3. myotonic
  4. oculopharyngeal
  5. limb girdle
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23
Q

what is muscular dystrophy

A

not enough dystrophin

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24
Q

excitation/contraction coupling.

the alpha motor neuron (LMN) releases _____ which binds to a nicotinic ACh receptor on the muscle fiber

this is happening at the motor end plate or aka

A

ACh

aka neuromuscular junction

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25
Q

this inhibits the release of ACh at the neuromuscular junction. it can be used in dentistry

A

botulinism toxin A

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26
Q

muscle twitch has 3 phases in order:

A
  1. latent period= muscle Action potential (really fast)
  2. contraction= muscle increase
  3. relaxation= of muscle
27
Q

what ap is first and what is right after that is second

A
  1. AP of alpha motor neuron is first
  2. ap of muscle is right after

(Na and K out)

28
Q

for contraction to happen, the intracellular _____ in the muscle fiber must increase

A

calcium

29
Q

in resting muscle, _______ prevents a strong bond between the myosin head and g-actin molecules

A

tropomyosin

30
Q

when troponin binds to cytosolic Ca2+, tropomyosin is:

A

pulled away from myosin binding site and allows for the power stroke

(myosin heads can then attach to actin)

31
Q

calcium is released from

A

the sarcoplasmic reticulum

32
Q

modified ER that sequesters(hide away) Ca2+

A

sarcoplasmic reticulum (SR)

33
Q

invaginations of sarcolemma

A

transverse (T)-tubules

34
Q

portion of SR that contact t-tubules

A

terminal cisternae

35
Q

the action potential travels down the membrane, down T-tubules and activates:
which are on the t-tubules

A

sensitive dihydropyridine (DHP) receptors

36
Q

DHP in turn open_____ on the SR. calicum goes from SR to the sarcoplasm

A

calcium channels (ryanodine receptors)

37
Q

the intracellular structure of_________ ensures spread of action potential (and calcium) throughout the cell

A

myocytes

38
Q

what is necessary for contraction?

A

atp

39
Q

ATP binding to the myosin head:

A

breaks the cross-bridge (connection between actin and myosin)

40
Q

energy released from ATP hydrolysis by the myosin head provides:

ATP-> ADP + Pi+energy

A

energy for cocking the myosin head (myosin is now in the high energy form)

41
Q

release of what from the myosin head provides energy for the POWER STROKE? which leads to

A

inorganic phosphate

(myosin head pulling actin towards the center of the sarcomere)

leads to sarcomere shortening

42
Q

muscle cells only have enough ATP for ~ _____ twitches

A

8 twitches

43
Q

cross-bridge cycling will stop only when

A

you run out of atp or ca2+

44
Q

both ___ and ___ produce ATP for muscle fibers

A

aerobic and anaerobic metabolism

45
Q

both aerobic and anaerobic metabolism produce ATP for muscle fibers. however, the contribution of each in a specific muscle fiber depends on:
1.
2.

A
  1. the metabolic enzymes are present in the cell (glycolytic vs. oxidative fibers)
  2. the intensity of the exercise
46
Q

when muscles are resting, they build up a bunch of:

which can use by adding ADP and CK to for ATP

A

phosphocreatine

47
Q

measurements of this in the blood is down to determine if damage to muscle tissue (skeletal and cardiac) has occurred

A

creatine kinase (CK)

48
Q

what happens if atp runs out

A

fatigue

49
Q

fatigue muscles:

A
  1. have decreased tension generation
  2. take longer to contract
  3. relax more slowly and may not completely relax
50
Q

theories for fatigue:

A
  1. change in membrane potential
  2. decreased ACH
  3. blockage of blood flow
  4. central fatigue
  5. increased metabolic byproducts (lactic acid or high K+ in ECF)
  6. depleted glycogen
51
Q

what 2 things must be present for cross-bridge cycling

A

both Ca and ATP

52
Q

cross-bridge cycling.

prior to atp binding, when myosin and actin are tightly bound

A

rigor state

53
Q

cross-bridge cycling.

step two, atp binds to ____, decreases its affinity for actin and the two separate

A

atp binds to myosin head

54
Q

cross-bridge cycling.

step 3, myosin head moves in the direction of the ______, ATP is_____

A

direction of the z-line

atp is hydrolyzed

55
Q

cross-bridge cycling.

step 4
myosin binds the next actin (one closer to z-line) and _____ occurs (pulls actin towards M-line

A

power stroke

56
Q

cross-bridge cycling.

step 5._____ is released and the actin and myosin resume to the rigor state

A

ADP

57
Q

to get relaxation of skeletal muscle, ______ must stop firing
and
____ must decrease
but ____ must be present to remove myosin from actin

A

alpha motor neuron stop firing and cytosolic (intracellular) calcium concen. decrease

atp must be present

58
Q

relaxation of skeletal muscle.

what removes calcium from cystol on SR

A

calcium ATPase

59
Q

what happens when atp is lost and myosin is stuck to actin

A

rigor mortis

60
Q

relaxation of skeletal muscle.

____ moves and covers actin’s myosin-binding site

A

tropomyosin

61
Q

relaxation of skeletal muscle.

actin slowly slides back to its original resting place and the ____ returns to its original length

A

sarcomere

62
Q

where is DHP?
where is ryanodine?

A

dhp= muscle membrane
ryanodine= SR

63
Q

botox works by

A

blocking ACH release

64
Q

what provides energy for power stroke

A

release of phosphate

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