Physiology of the Musculoskeletal System

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Physiology of the Musculoskeletal System

• Chapters 7 8

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1. Neuromuscular Anatomy
Pages 121-122, 126-129, 131, 136
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Nervous System
Central Nervous System
Peripheral Nervous System
Central Nervous System
Peripheral Nervous System
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Afferent Efferent
Afferent
Efferent
Central Nervous System
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Neuron
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Synapse
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Neuromuscular Junction
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Neuromuscular Junction
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Action Potential

• Electrical impluse
• Neurons and muscle fibers
• Two phases
• Depolarization
• Sodium (Na)
• Potassium (K)
• Repolarization
• Sodium (Na)
• Potassium (K)

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Action Potential
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Action Potential
Depolarization
Repolarization
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Motor Unit
Note This motor unit has a 31 ratio Actual
motor units range from 201 to 2,0001
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Motor Units

• 100-1000 per muscle
• Fast and Slow
• All-or-None Principle

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2. Muscle Anatomy Overview
Pages 141-152
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Muscle Fiber Anatomy
Note muscle fiber muscle cell
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Muscle Fiber Anatomy
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Sarcomere
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Myofibrils/Filaments - actin - myosin
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Actin Myosin
1. Troponin 2. Tropomyosin 3. Actin
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Actin Myosin
Actin
Myosin
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3. The Sliding Filament TheoryExcitation-Contract
ion Coupling
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Step-by-Step Summary of Excitation-Contraction
Coupling p. 145
Sliding filament theory
http//www.blackwellpublishing.com/matthews/myosin
.html
http//www.mhhe.com/biosci/esp/2002_general/Esp/fo
lder_structure/su/m4/s11/sum4s11_9.htm
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Neural Stimulation
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Action Potentials Acetylcholine
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Calcium
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Cross-Bridges Power Strokes
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Sliding
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Sliding
Relaxed
Partial
Maximal
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ATP (?)
1.
2.
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Quick Time Movie

• This Quick Time Movie of the contraction process
  can be downloaded at the class web page.

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Muscle Force

• Force The capacity to do work or cause physical
  change
• When in the sliding filament theory is muscle
  force actually produced?

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4. Types of Muscle Contraction

• Static contraction
• Isometric
• Dynamic contraction
• Concentric
• Eccentric

Pages 158-159
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Isometric
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Isometric or Static Contraction
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Concentric
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Concentric Contraction
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Eccentric Contraction
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Eccentric Contraction
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Eccentric Contraction
Lengthens
Lengthens
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5. Muscle Fiber Types
Most Common Slow twitch/Type I Fast twitch
A/Type IIa Fast twitch B/Type IIb
Type IIx
Pages 153-154
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Fiber Type Characteristics
Fast Fibers Slow
fibers Characteristic Type II Type I Resistance
to fatigue Low High Predominant energy
system Anaerobic Aerobic Speed of
shortening Fast Slow Force production High
Moderate Fiber Diameter Large Small Others
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Fiber Typing
FYI
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Fiber Typing
FYI
The things Ill do for extra credit!
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Fiber Typing
FYI
Type II
Type I
Type IIa
Type IIb
Type I
Fig 8.12
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Fiber Types and Individual Differences
Western States 100 two weeks later won Badwater
Ultramarathon
107.5 kg (237 lbs) at clean jerk in 1997.
Bodyweight was 53.1 kg (117 lbs).

• What are the percentages of fiber types in the
  average person?

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Fiber Type Distribution
Sport Type I Type II
Distance Runner 70-80 20-30
Track Sprinter 25-30 70-75
Non-athlete 47-53 47-53
Table 8.2
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Fiber Type Distribution

• Average person equal mix
• No sex difference
• No age difference

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Fiber Type Distribution
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Alterations in Fiber Types

• Shift
• skeletal muscle is highly plastic
• Complete change
• Fast twitch to Slow twitch
• rigorous and regular exercise

16 weeks of endurance training
6 increase in Type I
1 decrease in Type IIa
5 decrease in Type IIb
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6.Muscle Receptors
Pages 163-165
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Stretch Reflex

• stretch or increase length of the muscle...
• ...muscle contraction

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Golgi Tendon Organ
2.
1. Contraction
3.
4. Inhibition