Transcript Neuromuscular Fundamentals

Neuromuscular
Fundamentals
Anatomy and Kinesiology
420:024
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Outline
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Introduction
Structure and Function
Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension
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Introduction
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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:
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Muscle Tissue Properties
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Irritability or Excitability
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Contractility
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Extensibility
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Elasticity
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Outline
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Introduction
Structure and Function
Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension
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Structure and Function
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Nervous system structure
Muscular system structure
Neuromuscular function
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Figure 14.1, Marieb & Mallett (2003). Human Anatomy. Benjamin
Cummings.
Nervous System Structure
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Integration of information from millions of
sensory neurons  action via motor neurons
Figure 12.1, Marieb & Mallett (2003). Human Anatomy. Benjamin
Cummings.
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Nervous System Structure
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Organization
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Brain
Spinal cord
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Nerves
Fascicles
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Neurons
Figure 12.2, Marieb & Mallett (2003).
Human Anatomy. Benjamin Cummings.
Figure 12.7, Marieb & Mallett (2003). Human
Anatomy. Benjamin Cummings.
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Nervous System Structure
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Both sensory and motor neurons in nerves
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Figure 12.11, Marieb & Mallett (2003). Human Anatomy. Benjamin
Cummings.
Nervous System Structure
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The neuron: Functional unit of nervous tissue (brain,
spinal cord, nerves)
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Dendrites:
Cell body:
Axon:
 Myelin sheath:
 Nodes of Ranvier:
 Terminal branches:
 Axon terminals:
 Synaptic vescicles:
 Neurotransmitter:
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Dendrites
Cell body
Axon
Myelin sheath
Node of Ranvier
Terminal ending
Terminal branch
Figure 12.4, Marieb & Mallett (2003). Human
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Anatomy. Benjamin Cummings.
Figure 12.8, Marieb & Mallett (2003). Human Anatomy.
Benjamin Cummings.
Terminal ending
Synaptic vescicle
Neurotransmitter:
Acetylcholine (ACh)
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Figure 12.19, Marieb & Mallett (2003). Human Anatomy.
Benjamin Cummings.
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Structure and Function
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Nervous system structure
Muscular system structure
Neuromuscular function
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Classification of Muscle Tissue
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Three types:
1. Smooth muscle
2. Cardiac muscle
3. Skeletal muscle
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Muscular System Structure
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Organization:
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Muscle (epimyseum)
 Fascicle (perimyseum)
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Muscle fiber (endomyseum)
 Myofibril
 Myofilament
 Actin and myosin
Other Significant Structures:
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Sarcolemma
Transverse tubule
Sarcoplasmic reticulum
Tropomyosin
Troponin
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Figure 10.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Figure 10.4, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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http://staff.fcps.net/cverdecc/Adv%20A&P/Notes/Muscle%20Unit/sliding%20filament%20theory/slidin16.jpg
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Figure 10.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Structure and Function
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Nervous system structure
Muscular system structure
Neuromuscular function
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Neuromuscular Function
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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
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Nerve Impulse
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What is a nerve impulse?
-Transmitted electrical charge
-Excites or inhibits an action
-An impulse that travels along an axon is an
ACTION POTENTIAL
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Nerve Impulse
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How does a neuron send an impulse?
-Adequate stimulus from dendrite
-Depolarization of the resting membrane potential
-Repolarization of the resting membrane potential
-Propagation
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Nerve Impulse
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What is the resting membrane potential?
-Difference in charge between inside/outside of the
neuron
-70 mV
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Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Nerve Impulse
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What is depolarization?
-Reversal of the RMP from –70 mV to +30mV
Propagation of the
action potential
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Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Nerve Impulse
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What is repolarization?
-Return of the RMP to –70 mV
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Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
+30 mV
-70 mV
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Neuromuscular Function
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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
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Release of the
Neurotransmitter
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Action potential  axon terminals
1. Calcium uptake
2. Release of synaptic vescicles (ACh)
3. Vescicles release ACh
4. ACh binds sarcolemma
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Figure 12.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Ca2+
ACh
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Figure 14.5, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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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
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Ach
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AP Along the Sarcolemma
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Action potential  Transverse tubules
1. T-tubules carry AP inside
2. AP activates sarcoplasmic reticulum
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Figure 14.5, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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
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Calcium Release
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AP  T-tubules  Sarcoplasmic reticulum
1. Activation of SR
2. Calcium released into sarcoplasm
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CALCIUM
RELEASE
Sarcolemma
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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
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Coupling of Actin and Myosin
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Tropomyosin
Troponin
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Blocked
Coupling of actin and myosin
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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
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Sliding Filament Theory
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Basic Progression of Events
1. Cross-bridge
2. Power stroke
3. Dissociation
4. Reactivation of myosin
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Cross-Bridge
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Activation of myosin via ATP
-ATP  ADP + Pi + Energy
-Activation  “cocked” position
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Power Stroke
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ADP + Pi are released
Configurational change
Actin and myosin slide
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Dissociation
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New ATP binds to myosin
Dissociation occurs
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Reactivation of Myosin Head
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ATP  ADP + Pi + Energy
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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
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Outline
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Introduction
Structure and Function
Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension
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Shape of Muscles & Fiber
Arrangement
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Muscles have different shapes & fiber
arrangements
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Shape & fiber arrangement affects
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Shape of Muscles & Fiber
Arrangement
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Two major types of fiber arrangements
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Fiber Arrangement - Parallel
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Parallel muscles
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Categorized into following
shapes:
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Flat
Fusiform
Strap
Radiate
Sphincter or circular
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Fiber Arrangement - Parallel
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Flat muscles
Modified from Van De Graaff KM: Human
anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.
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Fiber Arrangement - Parallel
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Fusiform muscles
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Figure 3.3. Hamilton, Weimar & Luttgens (2005). Kinesiology:
Scientific basis for human motion. McGraw-Hill.
Fiber Arrangement - Parallel
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Strap muscles
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Figure 8.7. Hamilton, Weimar & Luttgens (2005). Kinesiology:
Scientific basis for human motion. McGraw-Hill.
Fiber Arrangement - Parallel
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Radiate muscles
Modified from Van De Graaff KM: Human
anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.
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Fiber Arrangement - Parallel
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Sphincter or circular muscles
Modified from Van De Graaff KM: Human
anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.
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Fiber Arrangement - Pennate
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Pennate muscles
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Fiber Arrangement - Pennate
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Categorized based upon the exact
arrangement between fibers & tendon
Modified from Van De Graaff KM: Human anatomy, ed
6, Dubuque, IA, 2002, McGraw-Hill.
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Fiber Arrangement - Pennate
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Unipennate muscles
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Fiber Arrangement - Pennate
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Bipennate muscle
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Fiber Arrangement - Pennate
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Multipennate muscles
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Bipennate & unipennate produce more
force than multipennate
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Outline
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
Introduction
Structure and Function
Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension
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Muscle Actions: Terminology
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Origin (Proximal Attachment):
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Muscle Actions: Terminology
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Insertion (Distal Attachment):
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Muscle Actions: Terminology
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When a particular muscle is activated:
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Examples:
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Bicep curl vs. chin-up
Hip extension vs. RDL
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Muscle Actions
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Action:
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Contraction:
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Muscle Actions
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Muscle actions can be used to cause,
control, or prevent joint movement or
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Types of Muscle Actions
MUSCLE ACTION (under tension)
Isometric
Isotonic
Concentric
Eccentric
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Types of Muscle Actions
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Isometric action:
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Types of Muscle Actions
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Isotonic (same tension):
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Isotonic contractions are either concentric
(shortening) or eccentric (lengthening)
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Types of Muscle Actions
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Concentric contractions involve muscle developing
tension as it shortens
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Eccentric contractions involve the muscle
lengthening under tension
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What is the role of the elbow extensors in
each phase?
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Modified from Shier D, Butler J, Lewis R: Hole’s human anatomy
& physiology, ed 9, Dubuque, IA, 2002, McGraw-Hill
Types of Muscle Actions
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Isokinetics:
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Types of Muscle Actions
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Movement may occur at any given joint
without any muscle contraction whatsoever
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Outline
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
Introduction
Structure and Function
Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension
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Role of Muscles
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Agonist muscles
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Role of Muscles
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Antagonist muscles
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Role of Muscles
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Stabilizers
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Role of Muscles
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Synergist
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Role of Muscles
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Neutralizers
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Outline
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Introduction
Structure and Function
Fiber Arrangement
Muscle Actions
Role of Muscles
Neural Control
Factors that Affect Muscle Tension
85
Factors That Affect Muscle
Tension
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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
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Number Coding & Rate Coding
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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
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Number Coding & Rate Coding
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Number of muscle fibers per motor unit
varies significantly
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Number Coding & Rate Coding
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As stimulus strength increases from threshold,
more motor units (Number Coding) are recruited &
overall muscle contraction force increases in a
graded fashion
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From Seeley RR, Stephens TD, Tate P: Anatomy & physiology,
ed 7, New York, 2006, McGraw-Hill.
Number Coding & Rate Coding
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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
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Stimulus
Latent period
Contraction phase
Relaxation phase
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Number Coding & Rate Coding
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Latent period
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Contraction phase
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Relaxation phase
From Powers SK, Howley ET: Exercise physiology: theory and
application to fitness and performance, ed 4, New York, 2001 ,
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McGraw-Hill.
Number Coding & Rate Coding
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Summation
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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
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Number Coding & Rate Coding
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Tetanus
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From Powers SK, Howley ET: Exercise physiology: theory and application to fitness and
performance, ed 4, New York, 2001 , McGraw-Hill.
All or None Principle
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Motor unit
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Typical muscle contraction
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All or None Principle
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Factors That Affect Muscle
Tension
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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
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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
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Length - Tension Relationship
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Generally, depending upon muscle
involved
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Length - Tension Relationship

Generally, depending upon muscle
involved
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Figure 20.2, Plowman and Smith (2002). Exercise Physiology, Benjamin
Cummings.
Factors That Affect Muscle
Tension
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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
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Force – Velocity Relationship
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When muscle is contracting (concentrically or
eccentrically) the rate of length change is
significantly related to the amount of force potential
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Force – Velocity Relationship
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Maximum concentric velocity = minimum
resistance
As load increases, concentric velocity
decreases
Eventually velocity = 0 (isometric action)
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Force – Velocity Relationship
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As load increases beyond muscle’s ability to
maintain an isometric contraction
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As load increases

Eventually
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Muscle Force – Velocity
Relationship
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Indirect relationship between force (load)
and concentric velocity
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Direct relationship between force (load)
and eccentric velocity
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Factors That Affect Muscle
Tension
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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
105
Angle of Pull
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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
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Angle of Pull
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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?
107
Angle of Pull

Rotary component - Acts perpendicular to
long axis of bone (lever)
Modified from Hall SJ: Basic biomechanics, New York,
2003, McGraw-Hill.
108
Angle of Pull

If angle < 90 degrees,
the parallel component
is a stabilizing force
What is the effect of >/< 90 deg on
ability to rotate the joint forcefully?

If angle > 90 degrees,
the force is a
dislocating force
109
Modified from Hall SJ: Basic biomechanics,
New York, 2003, McGraw-Hill.
Factors That Affect Muscle
Tension
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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
110
Uni Vs. Biarticular Muscles
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Uniarticular muscles
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Ex: Brachialis
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Ex: Gluteus Maximus
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Uni Vs. Biarticular Muscles
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Biarticular muscles
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May contract & cause motion at either one or
both of its joints
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Advantages over uniarticular muscles
112
Advantage #1
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Can cause and/or control motion at more
than one joint
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Advantage #2

Can maintain a relatively constant length
due to "shortening" at one joint and
"lengthening" at another joint (Quasiisometric)
- Recall the Length-Tension Relationship
114
Advantage #3
Prevention of Reciprocal Inhibition
This effect is negated with biarticular
muscles when they move concurrently
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Concurrent movement:
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Countercurrent movement:
115
What if the muscles of the
hip/knee were uniarticular?
Hip
Knee
Ankle
Muscles stretched/shortened to
116
extreme lengths! Implication?
117
Figure 20.2, Plowman and Smith (2002). Exercise Physiology, Benjamin
Cummings.
Quasi-isometric action?
Implication?
Hip
Knee
Ankle
118
Active & Passive Insufficiency

Countercurrent muscle actions can reduce the
effectiveness of the muscle
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As muscle shortens its ability to exert force
diminishes

As muscle lengthens its ability to move through
ROM or generate tension diminishes
119
Factors That Affect Muscle
Tension

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





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
120
Cross-Sectional Area
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
Hypertrophy vs. hyperplasia
Increased # of myofilaments
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Increased size and # of myofibrils
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Increased size of muscle fibers
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http://estb.msn.com/i/6B/917B20A6BE353420124115B1A511C7.jpg
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
122
Muscle Fiber Characteristics

Three basic types:
1. Type I:
-Slow twitch, oxidative, red
2. Type IIb:
-Fast twitch, glycolytic, white
3. Type IIa:
-FOG
123
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
124
Effect of Fiber Arrangement on
Force Output
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Concept #1: Force directly related to crosssectional 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
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