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602 EX 2 > muscle physiology 2 > Flashcards

muscle physiology 2 Flashcards

1
Q

What starts each contraction/power stroke?

A

Ca+ increases intracellularly

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2
Q

what happens when Ca+ increases intracellularly?

A
  1. Ca2+ binds troponin
  2. troponin rotates and causes the displacement of tropomyosin
    3.Binding sites on actin are now available
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3
Q

which ATPase model do we use? what is it?

A

Huxley

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4
Q

what causes myosin to release actin?

A

ATP attachment

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5
Q

what are the activation steps? (starting from ACh being released)

A
  1. Somatic motor neuron releases ACh at neuromuscular junction
  2. Na+ enters through ACh receptor channel initiates muscle AP
  3. AP in t-tubule changes conformation of Dihydropyridine (DHP) voltage receptor
  4. DHP receptor opens the Ca+ release channels in SR and Ca+ enders cytoplasm
  5. Ca+ binds to troponin allowing actin/myosin binding
  6. Myosin heads execute power stroke
  7. Actin filament slides to center of sarcomere
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6
Q

_______ sits at the junction between the I and A band and maintains SR Ca+ storage

A

T-tubule

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7
Q

what is inside T-tubules?

A

Extracellular (interstitial) fluid inside T tubules

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8
Q

________ sit on either side of the T-tubule

A

Lateral sacs/cisternae

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9
Q

________ + ______ = triad

A

T-tubule, 2 lateral sacs

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10
Q

_______ receptors are on lateral sac and ______ receptor on T-tubule

A

Ryanodine
DHP

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11
Q

_________ helps to reduce Ca gradient when you pump it back into SR, it makes the ATPase pump work more efficiently

A

Calsequestrian

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12
Q

how many Ca+ does Calsequestrian bind?

A

~43

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13
Q

what are the sequence of events in contraction? (starting at discharge of neuron)

A
  1. Discharge of neuron
  2. ACh release at motor end plate
  3. ACh binds nicotinic receptors
  4. Increase Na/K conductance
  5. Generation of endplate potential
  6. Generation of AP on sarcolemma
  7. Generation of AP in T-tubules
  8. SR (cisternas) release Ca+
    9.Ca+ binds troponin, which displaces tropomyosin
  9. Crossbriges form, then powerstroke, then shortening
  10. Ca+ actively taken up by SR when there is no longer an AP
  11. Tropomyosin slips back to its blocking position on actin, contraction ends, actin slides back to original resting position
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14
Q

where are these channels located?
1. Chemical gated ACh receptor
2. Voltage gated Na+ channels
3. Voltage gated Ryanodine, DPH

A
  1. end plate
  2. sarcolemma
  3. sarcoplasmic reticulum
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15
Q

bringing Ca+ back to SR goes _____ its concentration gradient

A

against

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16
Q

what are the sequence of events in relaxation?

A
  1. Ca actively pumped back into longitudinal membranes of SR, moved to cisterns, and bound to Calsequestrin (43 Ca+)
  2. Ca+ leaves troponin down a concentration gradient
  3. Tropomyosin and troponin move back into blocking position
  4. Cessation of actin + myosin interaction
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17
Q

what are the 3 things ATP is used for during contraction?

A
  1. Energy for power stroke
  2. Energy for release of myosin head from actin
  3. Ca+ pumps on SR (~30% ATP for a single twitch)
18
Q

____________ is the process by which depolarization of muscle fiber initiates contraction

A

Excitation-Contraction Coupling

19
Q

Electrical activity lasts about ______ while Mechanical activity lasts _______ and can start before electrical stimulation is over

A

1-2ms, ~7.5-100ms

20
Q

what type of fibers are at a motor end plate?

A

large myelinated A-alpha

21
Q

which neurotransmitter causes depolarization?

A

ACh

22
Q

______ breaks down ACh

A

acetylcholinesterase

23
Q

where are motor end plates located? why?

A

Located in middle of fiber so depolarization can spread evenly

24
Q

what are the steps at a motor end plate? (starting with AP coming down neuron)

A
  1. AP comes down motor neuron
  2. Voltage gated Ca+ channel opens
  3. Vesicles fuse and neurotransmitter (ACh) released out
  4. ACh binds to nicotinic receptors on postsynaptic membrane
  5. Na can now come in and K+ can leave → depolarization
  6. Depolarization of areas next to endplate lead to AP that spreads over sarcolemma
25
Q

what can happen if ACh is not destroyed?

A

muscle spasms, constitutive contraction, eventually muscle paralysis

26
Q

_____ is the limiting factor that limits the number of contractions per second

A

Muscle

27
Q

absolute refractory period for slow twitch muscle is ____ ma compared to A-alpha at ______ ms

A

1-3ms, <1ms

28
Q

_______ is the period of waiting in beginning of AP before you see contraction. what happens during this?

A

Latency period
-release of Ca, diffusion, binding to troponin, displacement of tropomyosin, myosin interacts with actin

29
Q

we have to build enough _____ to see displacement

A

tension

30
Q

slow fiber muscle electrical event spreads out at _____m/sec while A-alpha spreads out at _____m/sec

A

3-5
70-230

31
Q

total time for slow fiber AP is ______ sec, but total time for fast fiber AP is _______ sec

A

100ms, 20ms

32
Q

where are fast fibers usually seen?

A

places that do precise movement (like fingers)

33
Q

______ is a motor neuron and all the myofibers it innervates

A

Motor unit

34
Q

1 Aα can innervate _____ fine myofibers and _____ gross myofibers for their control of movement

A
  • ~3
  • ~2000
35
Q

Crossbridges made ______ give steady tension

A

asynchronously

36
Q

1 muscle can have _________ motor units of ______ types

A

many, different

37
Q

1 motor unit sends nerve fibers to_________________, but 1 motor unit can only innervate ________

A

myofibers located in different regions of the muscle,
one type of muscle fiber

38
Q

how many times is each myofiber innervated?

A

once

39
Q

what determines length of time one can hold light vs heavy objects? (give ex of it for heavy vs light?)

A

Asynchronous activity of motor units
-Light object = asynchronous
Heavy object = all motor units active at once

40
Q

even when not being stimulated, muscles show some slight degree of contraction, which is called _____

A

Tone

41
Q

what causes tone?

A

non-conscious cerebellum efferent stimulation or afferent-efferent spinal reflexes

602 EX 2 (13 decks)

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