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MSK - 2 - Biomechanics > Biomechanics of Skeletal Muscle > Flashcards

Biomechanics of Skeletal Muscle Flashcards

1
Q

Biomechanics

What is the difference between an Agonist and an Antagonist?

Skeletal Muscle

A

Agonists create joint movement
Antagonist oppose joint movement

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2
Q

Biomechanics

Describe the structural organization of skeletal muscle.

Skeletal Muscle

A
  • Muscles are made up of individual muscle fibers ( 10-100 micrometers x 1-50 cm)
  • Each muscle fiber is a muscle cell with multiple nuceli
  • Contractile proteins include action and myosin; non-contractile elements include connective tissue and titin, and desmin
  • Each muscle is covered in connective tissue called epimysium, fascicles of muscle fibers are covered in perimysium, and individual muscle fibers are covered in endomysium. Myofibrils within muscle fibers contain contractile proteins.
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3
Q

Biomechanics

Explain the sliding filament hypothesis.

Skeletal Muscle

A

In the sliding filament hypothesis, actin hinges on myosin and brings the sarcomeres z-disks together.

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4
Q

Biomechanics

Actin vs Myosin

Skeletal Muscle

A
  • Actin is the thin, light filament
  • Myosin is the thick, dark filament
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5
Q

Biomechanics

What is the contractile unit of muscle?

Skeletal Muscle

A

Sarcomere

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6
Q

Biomechanics

Fusiform vs. Pennate muscles

Skeletal Muscle

A
  • Fusiform muscles have fibers running parallel to one another and to central tendon
  • Pennate muscles possess fibers that approach their central tendon obliquely
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7
Q

Biomechanics

Do fusiform or pennate muscle produce greater maximal force? Why?

Skeletal Muscle

A

Pennate. Their fibers are oriented obliquely, so the muscle can fit more fibers into a given length of muscle.

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8
Q

Biomechanics

What are the A bands in the sarcomere?

Skeletal Muscle

A

Dark bands caused by presence of thick myosin myofilaments

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9
Q

Biomechanics

What are the I bands in the sarcomere?

Skeletal Muscle

A

Light bands caused by presence of thin actin myofilaments

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10
Q

Biomechanics

What are the H bands in the sarcomere?

Skeletal Muscle

A

Region within A band where actin and myosin do not overlap

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11
Q

Biomechanics

What are the M lines in the sarcomere?

Skeletal Muscle

A

Mid-region thickening of thick myosin myofilaments in center of H band

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12
Q

Biomechanics

What are the Z discs in the sarcomere?

Skeletal Muscle

A

The Z Discs help anchor thin actin myofilaments at connecting points between successive sarcomeres.

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13
Q

Biomechanics

Does eccentric or concentric have a higher total force? Why?

Skeletal Muscle

A

Eccentric has higher total force because it adds in both active force and passive tension

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14
Q

Biomechanics

What is a motor unit?

Skeletal Muscle

A

A group of muscles innervated by the same motor neuron.

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15
Q

Biomechanics

What does the Henneman Size Principle state?

Skeletal Muscle

A

Smaller neurons generally recruited before larger motor neurons
This principle is reversed with release of tension (first on = last off)

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16
Q

Biomechanics

What are the four main types of muscle fibers?

Skeletal Muscle

A

(Slow Twitch)
Type I
Type IIa
Type IIx
Type IIb
(Fast Twitch)

17
Q

Biomechanics

Skeletal Muscle

A
18
Q

Biomechanics

Skeletal Muscle

A
19
Q

Biomechanics

Skeletal Muscle

A
20
Q

Biomechanics

Skeletal Muscle

A
21
Q

Biomechanics

What two ways you can increase the force of a muscle contraction?

Skeletal Muscle

A
  • Increase the number of MU’s recruited
  • Increase the frequency of stimulation (frequency/rate coding)

This generally happens in that order.

22
Q

Biomechanics

What is meant by the term length-tension (force-length) relationship of a sarcomere?

Skeletal Muscle

A

The length-tension relationship of sarcomere describes how the force a sarcomere can produce changes with the length of the sarcomere and the associated number of available cross-bridging sites.

23
Q

Biomechanics

Explain the difference between isotonic, plyometric, and isokinetic

Skeletal Muscle

A

Isotonic: equal tension, doing eccentric and concentric movements
Plyometrics: muscle tendon complex stretched before a forceful contraction
Isokinetic: same speed throughout ROM; more a description of joint motion

24
Q

Biomechanics

What does reciprocal inhibition mean?

Skeletal Muscle

A

Relaxation of antagonist during contraction of agonist

25
Q

Biomechanics

Compare active and passive insufficiency.

Skeletal Muscle

A

Both concepts involve two-joint muscles placed at end-range.

  • Passive: A two-joint muscle concurrently lengthened at both joints is unable to attain full range-of-motion at both joints.
  • Active: A two-joint muscle shortened at both joints is limited in force production at both joints (especially the distal joint).

MSK - 2 - Biomechanics (16 decks)

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