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Neuromuscular Fundamentals

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Title: Neuromuscular Fundamentals


1
Neuromuscular Fundamentals
  • Anatomy and Physiology of Human Movement
  • 420050

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
  • Protection
  • Posture and support
  • Produce a major portion of total body heat
  • 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 - muscles work in groups
    rather than independently to achieve a given
    joint motion

4
Muscle Tissue Properties
  • Irritability or Excitability - property of muscle
    being sensitive or responsive to chemical,
    electrical, or mechanical stimuli
  • Contractility - ability of muscle to contract
    develop tension or internal force against
    resistance when stimulated
  • Extensibility - ability of muscle to be passively
    stretched beyond it normal resting length
  • Elasticity - ability of muscle to return to its
    original length following stretching

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 Receptor sites
  • Cell body Integration
  • Axon Transmission
  • Myelin sheath Protection and speed
  • Nodes of Ranvier Saltatory conduction
  • Terminal branches Increased innervation
  • Axon terminals Connection with muscular system
  • Synaptic vescicles Delivery mechanism of
    message
  • Neurotransmitter The message

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
Skeletal Muscle Properties
  • Extensibility The ability to lengthen
  • Contractility The ability to shorten
  • Elasticity The ability to return to original
    length
  • Irritability The ability to receive and respond
    to stimulus

18
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

19
Figure 10.1, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
20
Figure 10.4, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
21
http//staff.fcps.net/cverdecc/Adv20AP/Notes/Mus
cle20Unit/sliding20filament20theory/slidin16.jp
g
22
Figure 10.8, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
23
Structure and Function
  • Nervous system structure
  • Muscular system structure
  • Neuromuscular function

24
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

25
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

26
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

27
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.
28
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.
29
Nerve Impulse
  • What is repolarization?
  • -Return of the RMP to 70 mV

Figure 12.9, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
30
30 mV
-70 mV
31
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

32
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

33
Figure 12.8, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
Ca2
ACh
34
Figure 14.5, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
35
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

36
Ach
37
AP Along the Sarcolemma
  • Action potential ? Transverse tubules
  • 1. T-tubules carry AP inside
  • 2. AP activates sarcoplasmic reticulum

38
Figure 14.5, Marieb Mallett (2003). Human
Anatomy. Benjamin Cummings.
39
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

40
Calcium Release
  • AP ? T-tubules ? Sarcoplasmic reticulum
  • 1. Activation of SR
  • 2. Calcium released into sarcoplasm

41
CALCIUM RELEASE
Sarcolemma
42
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

43
Coupling of Actin and Myosin
  • Tropomyosin
  • Troponin

44
Blocked
Coupling of actin and myosin
45
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

46
Sliding Filament Theory
  • Basic Progression of Events
  • 1. Cross-bridge
  • 2. Power stroke
  • 3. Dissociation
  • 4. Reactivation of myosin

47
Cross-Bridge
  • Activation of myosin via ATP
  • -ATP ? ADP Pi Energy
  • -Activation ? cocked position

48
Power Stroke
  • ADP Pi are released
  • Configurational change
  • Actin and myosin slide

49
Dissociation
  • New ATP binds to myosin
  • Dissociation occurs

50
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

51
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52
Outline
  • Introduction
  • Structure and Function
  • Fiber Arrangement
  • Muscle Actions
  • Role of Muscles
  • Neural Control
  • Factors that Affect Muscle Tension

53
Shape of Muscles Fiber Arrangement
  • Muscles have different shapes fiber
    arrangements
  • Shape fiber arrangement affects
  • Muscles ability to exert force
  • Range through which it can effectively exert
    force onto the bones

54
Shape of Muscles Fiber Arrangement
  • Two major types of fiber arrangements
  • Parallel pennate
  • Each is further subdivided according to shape

55
Fiber Arrangement - Parallel
  • Parallel muscles
  • fibers arranged parallel to length of muscle
  • produce a greater range of movement than similar
    sized muscles with pennate arrangement
  • Categorized into following shapes
  • Flat
  • Fusiform
  • Strap
  • Radiate
  • Sphincter or circular

56
Fiber Arrangement - Parallel
  • Flat muscles
  • Usually thin broad, originating from broad,
    fibrous, sheet-like aponeuroses
  • Allows them to spread their forces over a broad
    area
  • Ex Rectus abdominus external oblique

Modified from Van De Graaff KM Human anatomy, ed
6, Dubuque, IA, 2002, McGraw-Hill.
57
Fiber Arrangement - Parallel
  • Fusiform muscles
  • Spindle-shaped with a central belly that tapers
    to tendons on each end
  • Allows them to focus their power onto small, bony
    targets
  • Ex Brachialis, biceps brachii

Figure 3.3. Hamilton, Weimar Luttgens (2005).
Kinesiology Scientific basis for human motion.
McGraw-Hill.
58
Fiber Arrangement - Parallel
  • Strap muscles
  • More uniform in diameter with essentially all
    fibers arranged in a long parallel manner
  • Enables a focusing of power onto small, bony
    targets
  • Ex Sartorius, sternocleidomastoid

Figure 8.7. Hamilton, Weimar Luttgens (2005).
Kinesiology Scientific basis for human motion.
McGraw-Hill.
59
Fiber Arrangement - Parallel
  • Radiate muscles
  • Also described sometimes as being triangular,
    fan-shaped or convergent
  • Have combined arrangement of flat fusiform
  • Originate on broad aponeuroses converge onto a
    tendon
  • Ex Pectoralis major, trapezius

Modified from Van De Graaff KM Human anatomy, ed
6, Dubuque, IA, 2002, McGraw-Hill.
60
Fiber Arrangement - Parallel
  • Sphincter or circular muscles
  • Technically endless strap muscles
  • Surround openings function to close them upon
    contraction
  • Ex Orbicularis oris surrounding the mouth

Modified from Van De Graaff KM Human anatomy, ed
6, Dubuque, IA, 2002, McGraw-Hill.
61
Fiber Arrangement - Pennate
  • Pennate muscles
  • Have shorter fibers
  • Arranged obliquely to their tendons in a manner
    similar to a feather
  • Reduces mechanical efficiency of each fiber
  • Increases overall number of fibers packed into
    muscle
  • Overall effect more crossbridges more force!

62
Fiber Arrangement - Pennate
  • Categorized based upon the exact arrangement
    between fibers tendon
  • Unipennate
  • Bipennate
  • Multipennate

Modified from Van De Graaff KM Human anatomy, ed
6, Dubuque, IA, 2002, McGraw-Hill.
63
Fiber Arrangement - Pennate
  • Unipennate muscles
  • Fibers run obliquely from a tendon on one side
    only
  • Ex Biceps femoris, extensor digitorum longus,
    tibialis posterior

64
Fiber Arrangement - Pennate
  • Bipennate muscle
  • Fibers run obliquely on both sides from a central
    tendon
  • Ex Rectus femoris, flexor hallucis longus

65
Fiber Arrangement - Pennate
  • Multipennate muscles
  • Have several tendons with fibers running
    diagonally between them
  • Ex Deltoid
  • Bipennate unipennate produce more force than
    multipennate

66
Outline
  • Introduction
  • Structure and Function
  • Fiber Arrangement
  • Muscle Actions
  • Role of Muscles
  • Neural Control
  • Factors that Affect Muscle Tension

67
Muscle Actions Terminology
  • Origin (Proximal Attachment)
  • Structurally, the proximal attachment of a muscle
    or the part that attaches closest to the midline
    or center of the body
  • Functionally historically, the least movable
    part or attachment of the muscle
  • Note The least movable may not necessarily be
    the proximal attachment

68
Muscle Actions Terminology
  • Insertion (Distal Attachment)
  • Structurally, the distal attachment or the part
    that attaches farthest from the midline or center
    of the body
  • Functionally historically, the most movable
    part is generally considered the insertion

69
Muscle Actions Terminology
  • When a particular muscle is activated
  • It tends to pull both ends toward the center
  • Actual movement is towards more stable attachment
  • Examples
  • Bicep curl vs. chin-up
  • Hip extension vs. RDL

70
Muscle Actions
  • Action - when tension is developed in a muscle as
    a result of a stimulus
  • Muscle contraction term is exclusive in nature
  • As a result, it has become increasingly common to
    refer to the various types of muscle contractions
    as muscle actions instead

71
Muscle Actions
  • Muscle actions can be used to cause, control, or
    prevent joint movement or
  • To initiate or accelerate movement of a body
    segment
  • To slow down or decelerate movement of a body
    segment
  • To prevent movement of a body segment by external
    forces

72
Types of Muscle Actions
  • Muscle action (under tension)
  • Isometric
  • Isotonic
  • Concentric
  • Eccentric

73
Types of Muscle Actions
  • Isometric action
  • Tension is developed within muscle but joint
    angles remain constant
  • AKA Static movement
  • May be used to prevent a body segment from being
    moved by external forces
  • Internal torque external torque

74
Types of Muscle Actions
  • Isotonic (same tension) contractions involve
    muscle developing tension to either cause or
    control joint movement
  • AKA Dynamic movement
  • Isotonic contractions are either concentric
    (shortening) or eccentric (lengthening)

75
Types of Muscle Actions
  • Concentric contractions involve muscle developing
    tension as it shortens
  • Internal torque gt external torque
  • Causes movement against gravity or other
    resistance
  • Described as being a positive action
  • Eccentric contractions involve the muscle
    lengthening under tension
  • External torque gt internal torque
  • Controls movement caused by gravity or other
    resistance
  • Described as being a negative action

76
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
77
Types of Muscle Actions
  • Movement may occur at any given joint without any
    muscle contraction whatsoever
  • referred to as passive
  • solely due to external forces such as those
    applied by another person, object, or resistance
    or the force of gravity in the presence of muscle
    relaxation

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
  • The activated muscle group during concentric or
    eccentric phases of movement
  • Known as primary or prime movers, or muscles most
    involved

80
Role of Muscles
  • Antagonist muscles
  • Located on opposite side of joint from agonist
  • Have the opposite concentric action
  • Also known as contralateral muscles
  • Work in cooperation with agonist muscles by
    relaxing allowing movement
  • Reciprocal Inhibition

81
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82
Role of Muscles
  • Stabilizers
  • Surround joint or body part
  • Contract to fixate or stabilize the area to
    enable another limb or body segment to exert
    force move
  • Also known as fixators

83
Role of Muscles
  • Synergist
  • Assist in action of agonists
  • Not necessarily prime movers for the action
  • Also known as guiding muscles
  • Assist in refined movement rule out undesired
    motions

84
Role of Muscles
  • Neutralizers
  • Counteract or neutralize the action of another
    muscle to prevent undesirable movements such as
    inappropriate muscle substitutions
  • Activation to resist specific actions of other
    muscles

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
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type

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
  • Activating those motor units containing a greater
    number of muscle fibers (Number Coding)
  • Activating more motor units (Number Coding)
  • Increasing the frequency of motor unit activation
    (Rate Coding)

88
Number Coding Rate Coding
  • Number of muscle fibers per motor unit varies
    significantly
  • From less than 10 in muscles requiring precise
    and detailed such as muscles of the eye
  • To as many as a few thousand in large muscles
    that perform less complex activities such as the
    quadriceps and gastrocnemius

89
Number Coding Rate Coding
  • Greater contraction forces may also be achieved
    by increasing the frequency or motor unit
    activation (Rate Coding)

90
All or None Principle
  • Motor unit
  • Single motor neuron all muscle fibers it
    innervates
  • Typical muscle contraction
  • The number of motor units responding (and number
    of muscle fibers contracting) within the muscle
    may vary significantly from relatively few to
    virtually all
  • All of the fibers within the motor unit will fire
    when stimulated by the CNS
  • All or None Principle - regardless of number,
    individual muscle fibers within a given motor
    unit will either fire contract maximally or not
    at all

91
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type

92
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
93
Figure 20.2, Plowman and Smith (2002). Exercise
Physiology, Benjamin Cummings.
94
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type

95
Force Velocity Relationship
  • When muscle is contracting (concentrically or
    eccentrically) the rate of length change is
    significantly related to the amount of force
    potential

96
Force Velocity Relationship
  • Maximum concentric velocity minimum resistance
  • As load increases, concentric velocity decreases
  • Eventually velocity 0 (isometric action)

97
Force Velocity Relationship
  • As load increases beyond muscles ability to
    maintain an isometric contraction, the muscle
    begins eccentric action
  • As load increases, eccentric velocity increases
  • Eventually velocity maximum when muscle tension
    fails

98
Muscle Force Velocity Relationship
  • Indirect relationship between force (load) and
    concentric velocity
  • Direct relationship between force (load) and
    eccentric velocity

99
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type

100
Uni Vs. Biarticular Muscles
  • Uniarticular muscles
  • Cross act directly only on the single joint
    that they cross
  • Ex Brachialis
  • Can only pull humerus ulna closer together
  • Ex Gluteus Maximus
  • Can only pull posterior femur and pelvis closer
    together

101
Uni Vs. Biarticular Muscles
  • Biarticular muscles
  • Cross act on two different joints
  • May contract cause motion at either one or both
    of its joints
  • Advantages over uniarticular muscles

102
Advantage 1
  • Can cause and/or control motion at more than one
    joint
  • Rectus femoris Knee extension, hip flexion
  • Hamstrings Knee flexion, hip extension

103
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

104
Advantage 3
  • Prevention of Reciprocal Inhibition
  • This effect is negated with biarticular muscles
    when they move concurrently
  • Concurrent movement
  • Concurrent lengthening and shortening of
    muscle
  • Countercurrent movement
  • Both ends lengthen or shorten

105
What if the muscles of the hip/knee were
uniarticular?
Hip
Knee
Ankle
Muscles stretched/shortened to extreme lengths!
Implication?
106
Figure 20.2, Plowman and Smith (2002). Exercise
Physiology, Benjamin Cummings.
107
Quasi-isometric action? Implication?
Hip
Knee
Ankle
108
Active Passive Insufficiency
  • Countercurrent muscle actions can reduce the
    effectiveness of the muscle
  • As muscle shortens its ability to exert force
    diminishes
  • Active insufficiency Diminished crossbridges
  • As muscle lengthens its ability to move through
    ROM or generate tension diminishes
  • Passively insufficiency Diminished crossbridges
    and excessive passive tension

109
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type

110
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
111
Factors That Affect Muscle Tension
  • Number Coding and Rate Coding
  • Length-Tension Relationship
  • Force-Velocity Relationship
  • Uniarticular vs. Biarticular Muscles
  • Cross-sectional Diameter
  • Muscle Fiber Type

112
Muscle Fiber Characteristics
  • Three basic types
  • 1. Type I
  • -Slow twitch, oxidative, red
  • 2. Type IIb
  • -Fast twitch, glycolytic, white
  • 3. Type IIa
  • -FOG
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