Muscular Considerations in Movement

1
Muscular Considerations in Movement
2
Introduction

• Properties of Skeletal Muscle
• Extensibility
• Elasticity
• Contractility
• Irritability
• Adaptability
• 2 parts to muscle
• Contractile Component
• Non-contractile Component

3
Gross Structure of Muscle Contractile Component

• Contractile Component
• Macroscopic Level
• Entire muscle encased in epimysium
• Each bundle of muscle fibers encased in
  perimysium
• Each Muscle fiber is a bundle of Myofibrils
• Bundle of Myofibrils encased in endomysium
• This is where the sarcomere is located

4
Myofibril

• Composition
• Sarcolemma
• Sarcoplasm
• Sarcoplasmic Reticulum
• Ca released
• T-tubules
• Sarcomere

5
Myofibril Zones

• Myofilaments
• Z-band
• A-band
• H-band
• I-band
• M-band

6
Myofilaments

• Thin Filament
• Actin
• F-actin
• G-actin
• Tropomyosin
• Troponin
• Globular structure
• Summary

7
Myofilaments

• Thick Filament
• Myosin Myosin Binding Proteins
• Composition of Myosin

8
Mechanics of Cross-bridge Cycle

• 1. Propagation of action potential along
  sarcolemma
• 2. Propagation of action potential down T-tubule
• Coupling of the action potential to the change in
  Ca conductance of the SR
• Release of CA from SR
• CA binds to Troponin
• Move tropomyosin off actin binding site
• Myosine crosssbridges (attaches to actin)

9
Cross-bridge Cycle Events

• M binds to A
• Movement of thin filament occurs
• Detachment of the cross-bridge
• Movement of the cross-bridge in a new position to
  repeat cycle

10
Summary of Contraction Mechanical Process
11
Non-Contractile Component of Muscle

• Parallel Elastic Component
• All CT in muscle interconnected
• Function in parallel
• Series Elastic Component
• Tendon cross-bridges
• Functions in series
• Like a spring can recoil

12
Gross Structure of Tendon

• Function
• Components
• Elastin
• Actin
• Fibronectin
• Water
• Collagen
• 86 of dry weight

13
Collagen Composition

• Fibril
• Fiber Arrangement

14
Musculo-tendinous Juntion

• Connection between myofribils fibrils
• Several folds increase strength
• Resist tensile forces

15
Osteo-tendinous Junction

• Characteristics

16
Mechanical Properties of Bone

• Resistance function of tendon length
• Differences in cross-sectional size and length

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Material Properties of Tendon

• Viscoelastic material
• Creep
• Hysteresis
• Response to Stretch

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Muscle Classification based on Fiber Arrangement

• Fusiform (Parallel) Arrangement

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Muscle Classification based on Fiber Arrangement

• Fusiform (Parallel) Arrangement
• Pennate Muscles
• Unipennate

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Muscle Classification based on Fiber Arrangement

• Fusiform (Parallel) Arrangement
• Pennate Muscles
• Unipennate
• Bipennate

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Muscle Classification based on Fiber Arrangement

• Fusiform (Parallel) Arrangement
• Pennate Muscles
• Unipennate
• Bipennate
• Multipennate

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Muscle Classification based on Fiber Arrangement

• Fusiform (Parallel) Arrangement
• Pennate Muscles
• Unipennate
• Bipennate
• Multipennate
• Triangular or Convergent Muscle
• Quadrate Muscle

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Mechanics of Pennate and Parallel Muscles

• Fusiform (Parallel)
• Long fibers but less fibers per cross sectional
  area
• Fast shortening speeds
• Move body segment through large ROM
• Pennate
• Greater number of fiber per cross sectional area
• Less ROM than parallel
• More force than parallel
• Slower shortening speed than parallel

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Muscle Characteristic Via Fiber Type

• Fast Twitch (Type IIb, FG)
• Intermediate Twitch (Type IIa, OG)
• Slow Twitch (Type I, O)

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Muscle Characteristic Via Articulations

• Uni-articulate Muscle

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Muscle Characteristic via Articulations

• Biarticulate Muscle
• Active Insufficiency
• Passive Insufficiency

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Types of Contraction

• Isometric
• Isotonic
• Concentric
• Eccentric

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Roles of Muscles

• Prime Mover vs Assistive mover
• Agonist (Movers)
• Antagonist

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Roles of Muscles

• Synergists
• Stabilizers, fixator and supporting role
• Contract statically to support or steady some part

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Roles of Muscles

• Synergists
• Stabilizers, fixator and supporting role
• Contract statically to support or steady some
  part
• Neutralizer
• Prevents unwanted accessory motion

31
Length-Tension Relationship

• Isometric tension greatest just beyond resting
  length
• Why?

32
Force-Velocity Relationship

• Concentric Contractions
• Inverse relationship
• Eccentric Contractions
• Direct relationship at a given velocity