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MSK > Muscle Physiology - skeletal > Flashcards

Muscle Physiology - skeletal Flashcards

1
Q
  • What type of muscle is shown in picture?
  • Strength?
  • Speed?
  • Voluntary or involuntary?
  • Appearance?
A
  • Skeletal
  • Strong
  • Quick
  • Voluntary
  • Striated, large long fibers with many peripheral nuclei
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2
Q
  • What type of muscle is shown in picture?
  • Strength
  • Speed
  • Voluntary or involuntary?
  • Appearance?
A
  • Weak
  • Slow
  • Involuntary
  • No striations, small cells with central nuceli
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3
Q
  • What type of muscle is this?
  • Strength?
  • Speed?
  • Voluntary or involuntary?
  • Appearance?
A
  • Cardiac
  • Strong
  • Quick
  • Involuntary, short, thick fibers with 1-2 central nuclei, striated
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4
Q
A
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5
Q

A skeletal muscle fiber (cell) is derived by merging 100s-1000s of […]

A

Myofibrils

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6
Q
  • How man nuclei are in skeletal muscle fibers?
  • Where are the nuclei located?
A
  • Many
  • In periphery of myofibrils
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7
Q
A
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8
Q

Do the filaments of the sarcomere shorten during muscle contraction?

A

NO - neither thick no thin shorten. Rather, the bands of the sarcomere shorten due to increased overlap between the thick and thin filaments.

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9
Q

What part(s) of the sarcomere shortens during contraction?

A

The I-band and the H-zone

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10
Q

What part of the sarcomere does not shorten during contraction?

A

The A band

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11
Q

The I-band is primariy […] filaments, aka […].

A

Thin filaments

Actin

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12
Q

The A-band is primarily […] filaments, aka […]

A

Thick

Myosin

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13
Q

What band of the sarcomere is only thick filaments?

A

H-band

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14
Q

The Z-line is the anchor for […] filaments and the M-line is the anchor for […] filaments.

A

Thin

Thick

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15
Q

What is titin? Where is it located in the sarcomere?

A

Titin is in the I-band with the thin filaments. It helps prevent overstrecthing of the sarcomere

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16
Q
A
17
Q

Is this muscle relaxed or contracted?

A

Contracted

18
Q

Is this muscle relaxed or contracted?

A

Relaxed

19
Q

Describe the structure of the thick filaments.

A
20
Q

Describe the structure of the thin filaments.

A
21
Q

Describe the structure and function of the troponin complex.

A
22
Q

Describe the contractile mechanism cross-bridge cycle.

A
23
Q

In relaxed skeletal muscle, what state of the cross-bridge cycle are muscle fibers in?

A

The “cocked” and energized position so that they are ready and waiting to bind to actin when Ca2+ moves tropomyosin out of the way

24
Q

What is rigor mortis?

A

During death, intracellular Ca2+ stores are released, causing exposure of myosin binding sites on actin filaments so energized myosin cross-bridges can bind to actin and perform the power stroke. However, there is not enough ATP in the body to release the myosin from the actin so the muscles remain contracted.

25
Q

What is the role of dystrophin in the sarcomere and why is it clinically relevant?

A

Dystrophin anchors the thin filaments to the sarcolemma by interacting with both thin filaments and glycoproteins embedded in membrane. It also helps with force generation.

Clinically relevant b/c when dystrophin is mutated or dysfunctional muscular dystrophy results.

26
Q

One motor neuron innervates only a single skeletal muscle fiber.

True/False.

A

False - can innervate 10s - 100s

27
Q

Each muscle fiber is innervated by only one motor neuron.

True/False

A

True

28
Q

What is a motor unit?

A

A motor neuron + the muscle fibers that it innervates.

29
Q

Describe the difference in motor unit size for the quadriceps compared to the extensor digiti minimi.

A

One axon can innervate either a large number of muscle fibers (quadriceps) and be a large motor unit or a small number of fibers (extensor digiti minimi) and be a small motor unit. This is necessary b/c finer muscle movement does not require activation of as many muscle fibers as gross movement.

30
Q

Much like action potential generation, muscle contraction is an […] phenomenon.

A

All or none

31
Q

What is the motor end plate?

A

The pocket formed around the motor neuron by the sarcolemma.

32
Q

What is the neuromuscular cleft?

A

The short gap between motor neuron and muscle fiber.

33
Q
A
34
Q

How is skeletal muscle contraction terminated?

A

By removal of calcium from troponin and a decrease in the cytosolic Ca2+ concentration. This is accomplished by pumping Ca2+ back into the sarcoplasmic reticulum via Ca2+ ATPase pump. However, it takes longer to return Ca2+ to SR than it does to release.

35
Q

What is this figure showing?

A

There is a standard amount of Ca2+ that is released with each AP. Therefore, the degree of skeletal muscle contraction is determined by the frequency and number of APs.

MSK (38 decks)

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