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KIN 316 - Biomechanics of Tissue > Module 5 - Biomechanics of Tissues > Flashcards

Module 5 - Biomechanics of Tissues Flashcards

1
Q

What contributes to the Force-Length Relationship?

A
  • Active Elements
  • Passive Elements
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2
Q

What is the Force-Length relationship as important as?

A
  • Effects of leverage
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3
Q

What is the Force-Length Relationship also known as?

A
  • Length-Tension Relationship
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4
Q

What are the Active parts of the Force-length relationship?

A
  • Thick Filament: Myosin
  • Thin Filament: Actin
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5
Q

What happens in an Ascending Limb?

A
  • Muscle force increases
  • 2 Subregions
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6
Q

What are the two subregions of the active part of the ascending limb?

A
  • Steep
  • Shallow
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7
Q

What is the steep subregion of the active part of an ascending limb?

A
  • Associated with force required to deform thick filament
  • F = 0 at 1.27um
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8
Q

What is the shallow subregion of the active part of an ascending limb?

A
  • Overlap of thin myofilaments
  • Actin filaments from one side overlap with those on the other side
  • Interferes with the formation of cross-bridges
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9
Q

What happens in a plateau region of the active part of the Force-Length?

A
  • Muscle Force remains constant
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10
Q

What does the plateau region correspond to?

A
  • central region of myosin fiber that does not have cross-bridge (0.2um)
  • If Greater Fiber overlap, no additional cross-bridge formation
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11
Q

What happens in the descending limb active part of the force-length relationship?

A

Muscle force decreases
- sarcomere length increases
- overlap between myosin and actin decrease
- decrease in the number of available cross-bridges
- Muscle force decreases until no overlap

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12
Q

Compare cross-species muscle force activation.

A
  • Length of thick filaments is approximately the same (1.6um)
  • Plateau and descending limb are identical (shifted)
  • Length of thin filament changes between species
  • Longer for humans: estimated 1.27um
  • The main difference occurs in ascending limb of force-length relationship
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13
Q

What is the main difference of force-length relationship between species?

A
  • Thin filament
  • Ascending limb
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14
Q

What are the effects of muscle fiber length (with identical physiological cross-sectional area)?

A
  • Increased muscle active range
  • Identical Maximal Tension, but occurs at longer muscle length
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15
Q

What are the effects of Muscle cross-sectional area (with identical muscle fiber length)?

A
  • Increased maximal tension
  • Muscle active range remains the same
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16
Q

Explain the passive part of the muscle force-length relationship.

A

Including the Muscle (not the tendon)
- Titin molecule spans half the sarcomere
- Titin corresponds to the passive mechanical properties of muscle

17
Q

What are the sources of passive tension in muscles?

A

Parallel
- Fascia Layers of Muscle
Series
- Possible role of Titin

18
Q

What is Titin?

A
  • Giant Protein: 10 times heavier than average protein
19
Q

Where is the Titin Molecule located?

A

Spans half the Sarcomere
- Z-band to M-line

20
Q

What does the Titin Molecule do?

A
  • Stabilizes myosin in the middle of the sarcomere
  • Influences the force-length relationship, both active and passive part
21
Q

What is the differences in Cardiac Muscle and the Soleus Muscle in relation to the Titin Molecule?

A
  • Cardiac Muscle is 10x stiffer than soleus muscle
  • Corresponds to changes in Titin molecule (number of amino acids)
22
Q

What are some examples of lower leg muscles with variations in the force-length relationship?

A

Semitendinosus
- Descending Limb
Rectus Femoris
- Ascending & Descending Limb
Gastrocnemius
- Ascending Limb

23
Q

What also must be applied to a patients muscle-joint system along with force-length relationship?

A
  • Geometry of the joint is also important to understand joint function/dysfunction
24
Q

Is the Rectus Femoris a Biarticular Muscle?

A

Yes
- Hip Flexor
- Knee Extensor

25
Q

What is the range of knee motion in running and cycling?

A
  • full extension 120 degrees
26
Q

What is the range of hip flexion in running and cycling?

A
  • Trunk-thigh angle of 25-30 degrees is expected in cycling
  • much greater angle for running
27
Q

How does the use of the rectus femoris vary between runners and cyclists?

A
  • Used at different lengths
  • Considerably longer for runners
28
Q

How does the rectus femoris contribute to knee extension in running and cycling?

A

Runners
- Strong at longer lengths
- Weak at shorter lengths
Cyclists
- Weak at longer lengths
- Strong at shorter lengths

29
Q

What are some possible explanations for the variation in runners and cycling rectus femoris usage?

A

Chronic Adaptation to Training
- Change in number of sarcomeres in series within a given muscle fiber of constant length
- Change in number os sarcomeres in series will change the optimal length of the muscle

30
Q

What happens with changes in the number of sarcomeres in series within a given muscle of constant length?

A
  • Change the optimal length of the muscle
31
Q

What is different between the active and passive muscle component contribution to force-length relationship?

A

Both contribute
- Passive only contributes at long sarcomere length

32
Q

What can training do to the force-length relationship?

A
  • May result in changes

KIN 316 - Biomechanics of Tissue (11 decks)

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