Download Section 2. Neuromuscular Fundamentals

Neuromuscular
Fundamentals
Anatomy and Physiology of
Human Movement
420:050
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Outline
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Introduction
Structure and Function
Muscle Actions
Role of Muscles
Neural Control
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Introduction
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Responsible for movement of body and all of its
joints
Muscles also provide
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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
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Muscle Tissue Properties
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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
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Outline
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Introduction
Structure and Function
Muscle Actions
Role of Muscles
Neural Control
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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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Figure 12.8, Marieb & Mallett (2003). Human Anatomy.
Benjamin Cummings.
Terminal ending
Synaptic vescicle
Neurotransmitter:
Acetylcholine (ACh)
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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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Skeletal Muscle: Properties
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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
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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
Muscle Actions
Role of Muscles
Neural Control
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Muscle Actions: Terminology
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Origin (Proximal Attachment):
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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
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Muscle Actions: Terminology
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Insertion (Distal Attachment):
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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
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Muscle Actions: Terminology
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When a particular muscle is activated
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It tends to pull both ends toward the center
Actual movement is towards more stable
attachment
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 - 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
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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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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
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Types of Muscle Actions
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Muscle action (under tension)
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Isometric
Isotonic
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Concentric
Eccentric
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Types of Muscle Actions
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Isometric action:
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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
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Types of Muscle Actions
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Isotonic (same tension) contractions involve
muscle developing tension to either cause or
control joint movement
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AKA – Dynamic movement
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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Internal torque > external torque
Causes movement against gravity or other resistance
Described as being a positive action
Eccentric contractions involve the muscle
lengthening under tension
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External torque > internal torque
Controls movement caused by gravity or other resistance
Described as being a negative action
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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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Movement may occur at any given joint
without any muscle contraction whatsoever
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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
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Outline





Introduction
Structure and Function
Muscle Actions
Role of Muscles
Neural Control
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Role of Muscles
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Agonist muscles
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The activated muscle group during concentric or
eccentric phases of movement
Known as primary or prime movers, or muscles
most involved
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Role of Muscles
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Antagonist muscles
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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
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Reciprocal Inhibition
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Role of Muscles
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Stabilizers
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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
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Role of Muscles
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Synergist
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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
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Role of Muscles
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Neutralizers
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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
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Muscle Fiber Characteristics
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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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