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physiology (Woods) > Skeletal Muscle Contraction > Flashcards

Skeletal Muscle Contraction Flashcards

1
Q

define epimysium

A

connective tissue surrounding entire muscle

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2
Q

define muscle

A

made up of multiple fascicles (each containing fiber)

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3
Q

define perimysium

A

connective tissue surrounding individual fascicle (typically thinner than epimysium)

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4
Q

define fascicle

A

a bundle of myofibers

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5
Q

define endomysium

A

delicate connective tissue around each myofiber

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6
Q

define sarcolemma (=plasmalemma)

A

cell membrane of muscle fiber

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7
Q

define myofiber (=muscle cell)

A

individual multinucleate muscle cell

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8
Q

define myofibril

A

chain of sarcomeres within a myofiber (intracellular configuration)

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9
Q

define myofilament

A

actin and myosin filaments that make up a sarcomere

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10
Q

what does sarco mean in greek

A

flesh

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11
Q

what are T-tubules

A
  • invaginations of sarcolemma
  • live close to cistern of SR
  • form triads with cistern
  • 2 per sarcomere
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12
Q

what are Z discs (lines)

A

anchor actin filaments

located at each of a sarcomere

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13
Q

what are I bands

A

composed of entirely actin
width changes during contraction
reflection of light

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14
Q

what are A bands

A

composed of actin and myosin
width does not change during contraction
reflection of light

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15
Q

what are H bands

A

composed entirely of myosin

width changes during contraction

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16
Q

what are the short-hand steps of muscle contraction

A
  1. action potential in alpha motor neuron
  2. Ca++ influx into axon terminal
  3. exocytosis of synaptic vesicles
  4. acetylcholine release into synaptic cleft
  5. diffusion of Ach across cleft
  6. binding of Ach to Ach receptors on sarcolemma
  7. opening of ligand-gated Na+ channels
  8. Na+ influx
  9. end-plate depolarization
  10. opening of voltage-gated Na+ channels
  11. sarcolemma action potential
  12. depolarization fo T-tubules
  13. Conformational change in DHP receptors
  14. conformational change in ryanodine receptors
  15. opening of ryanodine Ca++ channels
  16. release of Ca++ from SR
  17. Ca+ concentration in cytosol increases
  18. binding of Ca++ to Troponin
  19. Conformational change in troponin
  20. tropomyosin is pulled away from active sites on actin
  21. exposure of actin sites on actin
  22. binding of myosin heads to actin active sites
17
Q

what are characteristics of DHP receptors

A
  • voltage-sensitive L-type Ca++ channels arranged in quadruplets
  • located on the sarcolemma T-tubules
  • cause a conformational change in the ryanodine receptors
18
Q

what are characteristics of ryanodine receptors

A
  • located on the cisternae of SR
  • open in response to conformational change in DHP receptors
  • allow Ca++ into the cytosol from the SR
  • SERCA uses ATP to pump calcium back into the SR
19
Q

define preload

A

load on a muscle in the relaxed state before in contracts

20
Q

what are the types of tension

A

passive: produced by pre-load
active: produced by cross-bridging
total: sum of active and passive tension

21
Q

where is ATP required for muscle contraction

A
  • most used for the sliding filament mechanism
  • pumping Ca++ from Sarcoplasm back into SR
  • pumping sodium and K+ through the sarcolemma to re-restablish resting potential
22
Q

What is phosphocreatine

A
  • releases energy rapidly

* reconstitutes ATP

23
Q

compare isometric and isotonic contractions

A

isometric occurs when there is an increase in tension but not length while isotonic is when muscle length changes (lengthens=eccentric, shortens=concentric)

24
Q

compare white and red muscle fibers:

A

white are more rapid, have fewer mitochondria, primarily are anaerobic, little myoglobin and larger concentration of ATPase when compared to red

25
Q

what is soleus

A

muscles predominantly composed of dark fibers

26
Q

what is gastrocnemius

A

muscle predominantly composed of light fibers

27
Q

what is the difference between first-class, second-class, and 3rd class lever systems?

A

first class: fulcrum is in the middle (in force and out first move in opposite directions)
2nd class: resistance (outforce) is in the middle): both in and out forces are on the same side of the fulcrum
3rd: efforce (in force) is in the middle (both forces move in same direction)

28
Q

what is referred to as a chain of sarcomeres

A

myofibril

29
Q

which sarcoplasmic band does not undergo a change in length during the contraction of a skeletal muscle

A

A band

30
Q

which sarcomeric band is composed entirely of actin filaments

A

I band

31
Q

DHP channels are part of what structure

A

T tubules

32
Q

Ryanodine sensitive calcium ion release channels is part of what structure

A

SR

33
Q

what factor does the concentration of calcium increase in the cytosol after released from the SR

A

100

34
Q

what helps maintain the optimum calcium concentration gradient to facilitate return of calcium to SR

A

calsequestrin

35
Q

what is an example of eccentric contraction

A

the tricep muscle while lowering the body to the floor during a push up

36
Q

what is anchored to the presynaptic membrane and associated with synaptic vesicles to which they are tethered by short filaments

A

dense bar

37
Q

In order for acetylcholine-gated ion channels to open, how much Ach molecules are necessary to attach its alpha subunit

A

2

physiology (Woods) (18 decks)

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