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physiology IV > Skeletal Muscle Contraction > Flashcards

Skeletal Muscle Contraction Flashcards

1
Q

What is the Z line?

A

The boundary between two sarcomeres

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2
Q

What is the I band?

A

Composed of only actin filaments

  • extends from Z towards center of sarcomere
  • appears light
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3
Q

What is the A band?

A

Composed of myosin thick filaments

-appears dark

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4
Q

What is the H zone?

A

location of NO overlap between actin and myosin

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5
Q

What is the M-line?

A

The center of the sarcomere

-site where thick filaments are linked with eachother

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6
Q

What occurs to the Z lines, A bands, I bands during muscle contraction?

A
  1. Z lines move closer together
  2. Length of A band is constant
  3. Length of I band shortens
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7
Q

What is a myosin molecule made up of?

A

-2 heavy chains
-4 light chains
2 regulatory chains
2 essential or alkali chains

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8
Q

What is a myosin filament made up of ?

A

200 or more individual myosin molecules

-equal to the length of the A band

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9
Q

What are the 6 steps involved in excitation coupling (innervation) of a skeletal muscle ?

A
  1. Motor AP travels along motor neuron to motor endplate at neuromusc junction
  2. ACh released – acts on sarcolemma
  3. Trigger AP in muscle
  4. Propagates down T-tubule membranes into interior of muscle fibers
  5. causes release of ca2+ sequestered in SR (inside the cell)
  6. Leads to shortening of sarcomere
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10
Q

How is a muscle lengthened?

A

By innervation and contraction of an antagonist muscle

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11
Q

What does each bind to:

  1. Troponin C
  2. Tropoinin I
  3. Troponin T
A
  1. c binds calcium
  2. I binds actin - inhibits actomyosin ATPase
  3. T binds to tropomyosin
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12
Q

What is the cycle of contraction in a sarcomere, starting when the myosin head is in an attached state? (5 steps)

A
  1. ATP binds to myosin head -dissociation
  2. ATP is hydrolyzed-myosin heads to return to resting conformation
  3. A crossbridge forms and myosin head binds to new position on actin
  4. P is released. Myosin heads change conformation
  5. ADP is released
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13
Q

How much energy is stored in ATP as it is transformed into mechanical work in the crossbridge cycle?

A

30%!!

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14
Q

What is the contraction generated by a single action potential called?

A

A twitch

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15
Q

What is genetically distinct between the slow twitch, and two fast twitch fibers?

A

They differ in the myosin heavy chain they encode for

  • different rates of ATP hydrolysis
  • influence speed of crossbridge cycle and muscle contraction
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16
Q

Describe the phases of a graph for an isometric contraction - tension vs time

A
  1. latent period
  2. contraction phase
  3. relaxation phase
17
Q

What is the active tension ?

A

The difference between total tension and passive tension

18
Q

When is tension of the muscle the greatest?

A

When there is maximal overlap between thick and thin filaments - number of crossbridges is the greatest

19
Q

At which two states does zero tension exist in a muscle?

A
  • When the muscle is stretched beyond the optimal length and there is no thin and thick overlap
  • When the thick filaments contact the Z lines
20
Q

What are satellite cells?

A

-Quiescent undifferentiated cells which mediate repair and growth

21
Q

How do satellite cells assist in growth of skeletal muscle?

A

-They fuse into existing multinucleate myofibers and increase myofibril protein production

22
Q

What is the result of a loss of myostatin in the mice experiment?

A
  • uncontrolled hypertrophy

- altered satellite activation

23
Q

What is the drug MYO-029?

A
  • recombinant human AB that binds to inhibit myostatin activity
  • used to treat muscular dystrophy
24
Q

Describe a slow twitch fiber:

  1. other name
  2. Fatigue
  3. Color
A
  1. Type I
  2. resistant
  3. red - myoglobin
25
Q

Describe a fast twitch iia fiber:

  1. Fatigue
  2. color
A
  1. Resistant

2. Red-myoglobin

26
Q

Describe a fast twitch IIB fiber:

  1. fatigue
  2. color
A
  1. fatigable

2. white - low myoglobin

27
Q

Describe a slow twitch fiber:

  1. metabolism
  2. mitochondria content
  3. glycogen level
A
  1. oxidative
  2. high
  3. low
28
Q

Describe a fast twitch IIA fiber:

  1. metabolism
  2. mitochondria content
  3. glycogen level
A
  1. Oxidative
  2. Highest
  3. abundant
29
Q

Describe a fast twitch IIb fiber:

  1. metabolism
  2. mitochondria content
  3. glycogen level
A
  1. Glycolytic
  2. few
  3. high

physiology IV (40 decks)

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