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Neuromuscular Fundamentals

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Title: Neuromuscular Fundamentals


1
Neuromuscular Fundamentals
  • Anatomy and Kinesiology
  • 420024

2
Outline
  • Introduction
  • Structure and Function
  • Fiber Arrangement
  • Muscle Actions
  • Role of Muscles
  • Neural Control
  • Factors that Affect Muscle Tension

3
Introduction
  • Responsible for movement of body and all of its
    joints
  • Muscles also provide
  • Over 600 skeletal muscles comprise approximately
    40 to 50 of body weight
  • 215 pairs of skeletal muscles usually work in
    cooperation with each other to perform opposite
    actions at the joints which they cross
  • Aggregate muscle action

4
Muscle Tissue Properties
  • Irritability or Excitability
  • Contractility
  • Extensibility
  • Elasticity

5
Outline
  • Introduction
  • Structure and Function
  • Fiber Arrangement
  • Muscle Actions
  • Role of Muscles
  • Neural Control
  • Factors that Affect Muscle Tension

6
Structure and Function
  • Nervous system structure
  • Muscular system structure
  • Neuromuscular function

7
Figure 14.1, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
8
Nervous System Structure
  • Integration of information from millions of
    sensory neurons ? action via motor neurons

Figure 12.1, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
9
Nervous System Structure
  • Organization
  • Brain
  • Spinal cord
  • Nerves
  • Fascicles
  • Neurons

Figure 12.2, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
Figure 12.7, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
10
Nervous System Structure
  • Both sensory and motor neurons in nerves

Figure 12.11, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
11
Nervous System Structure
  • The neuron Functional unit of nervous tissue
    (brain, spinal cord, nerves)
  • Dendrites
  • Cell body
  • Axon
  • Myelin sheath
  • Nodes of Ranvier
  • Terminal branches
  • Axon terminals
  • Synaptic vescicles
  • Neurotransmitter

12
Dendrites
Cell body
Axon
Myelin sheath
Node of Ranvier
Terminal ending
Terminal branch
Figure 12.4, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
13
Figure 12.8, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
Terminal ending
Synaptic vescicle
Neurotransmitter Acetylcholine (ACh)
14
Figure 12.19, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
15
Structure and Function
  • Nervous system structure
  • Muscular system structure
  • Neuromuscular function

16
Classification of Muscle Tissue
  • Three types
  • 1. Smooth muscle
  • 2. Cardiac muscle
  • 3. Skeletal muscle

17
Muscular System Structure
  • Organization
  • Muscle (epimyseum)
  • Fascicle (perimyseum)
  • Muscle fiber (endomyseum)
  • Myofibril
  • Myofilament
  • Actin and myosin
  • Other Significant Structures
  • Sarcolemma
  • Transverse tubule
  • Sarcoplasmic reticulum
  • Tropomyosin
  • Troponin

18
Figure 10.1, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
19
Figure 10.4, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
20
http//staff.fcps.net/cverdecc/Adv20AP/Notes/Mus
cle20Unit/sliding20filament20theory/slidin16.jp
g
21
Figure 10.8, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
22
Structure and Function
  • Nervous system structure
  • Muscular system structure
  • Neuromuscular function

23
Neuromuscular Function
  • Basic Progression
  • 1. Nerve impulse
  • 2. Neurotransmitter release
  • 3. Action potential along sarcolemma
  • 4. Calcium release
  • 5. Coupling of actin and myosin
  • 6. Sliding filaments

24
Nerve Impulse
  • What is a nerve impulse?
  • -Transmitted electrical charge
  • -Excites or inhibits an action
  • -An impulse that travels along an axon is an
    ACTION POTENTIAL

25
Nerve Impulse
  • How does a neuron send an impulse?
  • -Adequate stimulus from dendrite
  • -Depolarization of the resting membrane
    potential
  • -Repolarization of the resting membrane
    potential
  • -Propagation

26
Nerve Impulse
  • What is the resting membrane potential?
  • -Difference in charge between inside/outside of
    the neuron

-70 mV
Figure 12.9, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
27
Nerve Impulse
  • What is depolarization?
  • -Reversal of the RMP from 70 mV to 30mV

Propagation of the action potential
Figure 12.9, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
28
Nerve Impulse
  • What is repolarization?
  • -Return of the RMP to 70 mV

Figure 12.9, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
29
30 mV
-70 mV
30
Neuromuscular Function
  • Basic Progression
  • 1. Nerve impulse
  • 2. Neurotransmitter release
  • 3. Action potential along sarcolemma
  • 4. Calcium release
  • 5. Coupling of actin and myosin
  • 6. Sliding filaments

31
Release of the Neurotransmitter
  • Action potential ? axon terminals
  • 1. Calcium uptake
  • 2. Release of synaptic vescicles (ACh)
  • 3. Vescicles release ACh
  • 4. ACh binds sarcolemma

32
Figure 12.8, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
Ca2
ACh
33
Figure 14.5, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
34
Neuromuscular Function
  • 1. Nerve impulse
  • 2. Neurotransmitter release
  • 3. Action potential along sarcolemma
  • 4. Calcium release
  • 5. Coupling of actin and myosin
  • 6. Sliding filaments

35
Ach
36
AP Along the Sarcolemma
  • Action potential ? Transverse tubules
  • 1. T-tubules carry AP inside
  • 2. AP activates sarcoplasmic reticulum

37
Figure 14.5, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
38
Neuromuscular Function
  • 1. Nerve impulse
  • 2. Neurotransmitter release
  • 3. Action potential along sarcolemma
  • 4. Calcium release
  • 5. Coupling of actin and myosin
  • 6. Sliding Filaments

39
Calcium Release
  • AP ? T-tubules ? Sarcoplasmic reticulum
  • 1. Activation of SR
  • 2. Calcium released into sarcoplasm

40
CALCIUM RELEASE
Sarcolemma
41
Neuromuscular Function
  • 1. Nerve impulse
  • 2. Neurotransmitter release
  • 3. Action potential along sarcolemma
  • 4. Calcium release
  • 5. Coupling of actin and myosin
  • 6. Sliding filaments

42
Coupling of Actin and Myosin
  • Tropomyosin
  • Troponin

43
Blocked
Coupling of actin and myosin
44
Neuromuscular Function
  • 1. Nerve impulse
  • 2. Neurotransmitter release
  • 3. Action potential along sarcolemma
  • 4. Calcium release
  • 5. Coupling of actin and myosin
  • 6. Sliding filaments

45
Sliding Filament Theory
  • Basic Progression of Events
  • 1. Cross-bridge
  • 2. Power stroke
  • 3. Dissociation
  • 4. Reactivation of myosin

46
Cross-Bridge
  • Activation of myosin via ATP
  • -ATP ? ADP Pi Energy
  • -Activation ? cocked position

47
Power Stroke
  • ADP Pi are released
  • Configurational change
  • Actin and myosin slide

48
Dissociation
  • New ATP binds to myosin
  • Dissociation occurs

49
Reactivation of Myosin Head
  • ATP ? ADP Pi Energy
  • Reactivates the myosin head
  • Process starts over
  • Process continues until
  • -Nerve impulse stops
  • -AP stops
  • -Calcium pumped back into SR
  • -Tropomyosin/troponin back to original position

50
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51
Outline
  • Introduction
  • Structure and Function
  • Fiber Arrangement
  • Muscle Actions
  • Role of Muscles
  • Neural Control
  • Factors that Affect Muscle Tension

52
Shape of Muscles Fiber Arrangement
  • Muscles have different shapes fiber
    arrangements
  • Shape fiber arrangement affects

53
Shape of Muscles Fiber Arrangement
  • Two major types of fiber arrangements

54
Fiber Arrangement - Parallel
  • Parallel muscles
  • Categorized into following shapes
  • Flat
  • Fusiform
  • Strap
  • Radiate
  • Sphincter or circular

55
Fiber Arrangement - Parallel
  • Flat muscles

Modified from Van De Graaff KM Human anatomy, ed
6, Dubuque, IA, 2002, McGraw-Hill.
56
Fiber Arrangement - Parallel
  • Fusiform muscles

Figure 3.3. Hamilton, Weimar Luttgens (2005).
Kinesiology Scientific basis for human motion.
McGraw-Hill.
57
Fiber Arrangement - Parallel
  • Strap muscles

Figure 8.7. Hamilton, Weimar Luttgens (2005).
Kinesiology Scientific basis for human motion.
McGraw-Hill.
58
Fiber Arrangement - Parallel
  • Radiate muscles

Modified from Van De Graaff KM Human anatomy, ed
6, Dubuque, IA, 2002, McGraw-Hill.
59
Fiber Arrangement - Parallel
  • Sphincter or circular muscles

Modified from Van De Graaff KM Human anatomy, ed
6, Dubuque, IA, 2002, McGraw-Hill.
60
Fiber Arrangement - Pennate
  • Pennate muscles

61
Fiber Arrangement - Pennate
  • Categorized based upon the exact arrangement
    between fibers tendon

Modified from Van De Graaff KM Human anatomy, ed
6, Dubuque, IA, 2002, McGraw-Hill.
62
Fiber Arrangement - Pennate
  • Unipennate muscles

63
Fiber Arrangement - Pennate
  • Bipennate muscle

64
Fiber Arrangement - Pennate
  • Multipennate muscles
  • Bipennate unipennate produce more force than
    multipennate

65
Outline
  • Introduction
  • Structure and Function
  • Fiber Arrangement
  • Muscle Actions
  • Role of Muscles
  • Neural Control
  • Factors that Affect Muscle Tension

66
Muscle Actions Terminology
  • Origin (Proximal Attachment)

67
Muscle Actions Terminology
  • Insertion (Distal Attachment)

68
Muscle Actions Terminology
  • When a particular muscle is activated
  • Examples
  • Bicep curl vs. chin-up
  • Hip extension vs. RDL

69
Muscle Actions
  • Action
  • Contraction

70
Muscle Actions
  • Muscle actions can be used to cause, control, or
    prevent joint movement or

71
Types of Muscle Actions
MUSCLE ACTION (under tension)
72
Types of Muscle Actions
  • Isometric action

73
Types of Muscle Actions
  • Isotonic (same tension)
  • Isotonic contractions are either concentric
    (shortening) or eccentric (lengthening)

74
Types of Muscle Actions
  • Concentric contractions involve muscle developing
    tension as it shortens
  • Eccentric contractions involve the muscle
    lengthening under tension

75
What is the role of the elbow extensors in each
phase?
Modified from Shier D, Butler J, Lewis R Holes
human anatomy physiology, ed 9, Dubuque, IA,
2002, McGraw-Hill
76
Types of Muscle Actions
  • Isokinetics

77
Types of Muscle Actions
  • Movement may occur at any given joint without any
    muscle contraction whatsoever

78
Outline
  • Introduction
  • Structure and Function
  • Fiber Arrangement
  • Muscle Actions
  • Role of Muscles
  • Neural Control
  • Factors that Affect Muscle Tension

79
Role of Muscles
  • Agonist muscles

80
Role of Muscles
  • Antagonist muscles

81
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82
Role of Muscles
  • Stabilizers

83
Role of Muscles
  • Synergist

84
Role of Muscles
  • Neutralizers

85
Outline
  • Introduction
  • Structure and Function
  • Fiber Arrangement
  • Muscle Actions
  • Role of Muscles
  • Neural Control
  • Factors that Affect Muscle Tension

86
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Angle of Pull
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type
  • Pennation

87
Number Coding Rate Coding
  • Difference between lifting a minimal vs. maximal
    resistance is the number of muscle fibers
    recruited (crossbridges)
  • The number of muscle fibers recruited may be
    increased by

88
Number Coding Rate Coding
  • Number of muscle fibers per motor unit varies
    significantly

89
Number Coding Rate Coding
  • As stimulus strength increases from threshold,
    more motor units (Number Coding) are recruited
    overall muscle contraction force increases in a
    graded fashion

From Seeley RR, Stephens TD, Tate P Anatomy
physiology, ed 7, New York, 2006, McGraw-Hill.
90
Number Coding Rate Coding
  • Greater contraction forces may also be achieved
    by increasing the frequency or motor unit
    activation (Rate Coding)
  • Phases of a single muscle fiber contraction or
    twitch
  • Stimulus
  • Latent period
  • Contraction phase
  • Relaxation phase

91
Number Coding Rate Coding
  • Latent period
  • Contraction phase
  • Relaxation phase

From Powers SK, Howley ET Exercise physiology
theory and application to fitness and
performance, ed 4, New York, 2001 , McGraw-Hill.
92
Number Coding Rate Coding
  • Summation
  • When successive stimuli are provided before
    relaxation phase of first twitch has completed,
    subsequent twitches combine with the first to
    produce a sustained contraction
  • Generates a greater amount of tension than single
    contraction would produce individually
  • As frequency of stimuli increase, the resultant
    summation increases accordingly producing
    increasingly greater total muscle tension

93
Number Coding Rate Coding
  • Tetanus

From Powers SK, Howley ET Exercise physiology
theory and application to fitness and
performance, ed 4, New York, 2001 , McGraw-Hill.
94
All or None Principle
  • Motor unit
  • Typical muscle contraction
  • All or None Principle

95
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Angle of Pull
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type
  • Pennation

96
Length - Tension Relationship
  • Maximal ability of a muscle to develop tension
    exert force varies depending upon the length of
    the muscle during contraction

Passive Tension
Active Tension
97
Length - Tension Relationship
  • Generally, depending upon muscle involved

98
Length - Tension Relationship
  • Generally, depending upon muscle involved

99
Figure 20.2, Plowman and Smith (2002). Exercise
Physiology, Benjamin Cummings.
100
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Angle of Pull
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type
  • Pennation

101
Force Velocity Relationship
  • When muscle is contracting (concentrically or
    eccentrically) the rate of length change is
    significantly related to the amount of force
    potential

102
Force Velocity Relationship
  • Maximum concentric velocity minimum resistance
  • As load increases, concentric velocity decreases
  • Eventually velocity 0 (isometric action)

103
Force Velocity Relationship
  • As load increases beyond muscles ability to
    maintain an isometric contraction
  • As load increases
  • Eventually

104
Muscle Force Velocity Relationship
  • Indirect relationship between force (load) and
    concentric velocity
  • Direct relationship between force (load) and
    eccentric velocity

105
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Angle of Pull
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type
  • Pennation

106
Angle of Pull
  • Angle between the line of pull of the muscle
    the bone on which it inserts (angle toward the
    joint)
  • With every degree of joint motion, the angle of
    pull changes
  • Joint movements insertion angles involve mostly
    small angles of pull

107
Angle of Pull
  • Angle of pull changes as joint moves through ROM
  • Most muscles work at angles of pull less than 50
    degrees
  • Amount of muscular force needed to cause joint
    movement is affected by angle of pull Why?

108
Angle of Pull
  • Rotary component - Acts perpendicular to long
    axis of bone (lever)

Modified from Hall SJ Basic biomechanics, New
York, 2003, McGraw-Hill.
109
Angle of Pull
  • If angle lt 90 degrees, the parallel component is
    a stabilizing force
  • If angle gt 90 degrees, the force is a dislocating
    force

What is the effect of gt/lt 90 deg on ability to
rotate the joint forcefully?
Modified from Hall SJ Basic biomechanics, New
York, 2003, McGraw-Hill.
110
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Angle of Pull
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type
  • Pennation

111
Uni Vs. Biarticular Muscles
  • Uniarticular muscles
  • Ex Brachialis
  • Ex Gluteus Maximus

112
Uni Vs. Biarticular Muscles
  • Biarticular muscles
  • May contract cause motion at either one or both
    of its joints
  • Advantages over uniarticular muscles

113
Advantage 1
  • Can cause and/or control motion at more than one
    joint

114
Advantage 2
  • Can maintain a relatively constant length due to
    "shortening" at one joint and "lengthening" at
    another joint (Quasi-isometric)
  • - Recall the Length-Tension Relationship

115
Advantage 3
  • Prevention of Reciprocal Inhibition
  • This effect is negated with biarticular muscles
    when they move concurrently
  • Concurrent movement
  • Countercurrent movement

116
What if the muscles of the hip/knee were
uniarticular?
Hip
Knee
Ankle
Muscles stretched/shortened to extreme lengths!
Implication?
117
Figure 20.2, Plowman and Smith (2002). Exercise
Physiology, Benjamin Cummings.
118
Quasi-isometric action? Implication?
Hip
Knee
Ankle
119
Active Passive Insufficiency
  • Countercurrent muscle actions can reduce the
    effectiveness of the muscle
  • As muscle shortens its ability to exert force
    diminishes
  • As muscle lengthens its ability to move through
    ROM or generate tension diminishes

120
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Angle of Pull
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type
  • Pennation

121
Cross-Sectional Area
  • Hypertrophy vs. hyperplasia
  • Increased of myofilaments
  • Increased size and of myofibrils
  • Increased size of muscle fibers

http//estb.msn.com/i/6B/917B20A6BE353420124115B1A
511C7.jpg
122
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Angle of Pull
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type
  • Reflexes
  • Pennation

123
Muscle Fiber Characteristics
  • Three basic types
  • 1. Type I
  • -Slow twitch, oxidative, red
  • 2. Type IIb
  • -Fast twitch, glycolytic, white
  • 3. Type IIa
  • -FOG

124
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Angle of Pull
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type
  • Reflexes
  • Pennation

125
Effect of Fiber Arrangement on Force Output
  • Concept 1 Force directly related to
    cross-sectional area ? more fibers
  • Example Thick vs. thin longitudinal/fusiform
    muscle?
  • Example Thick fusiform/longitudinal vs. thick
    bipenniform muscle?
  • Concept 2 As degree of pennation increases, so
    does of fibers per CSA

126
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