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ELAINE N. MARIEB
EIGHTH EDITION
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
The Muscular System
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Function of Muscles
Produce movement
(chemical E to mechanical E)
Maintain body form and shape (posture)
Stabilize joints
Generate heat (75% of ATP E)
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Characteristics of Muscles
Muscle cells are elongated
(muscle cell = muscle fiber)
Contraction of muscles is due to the
movement of myofilaments (actin & myosin)
All muscles share some terminology
Prefix myo refers to muscle
Prefix mys refers to muscle
Prefix sarco refers to flesh
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The Muscular System
Muscles are responsible for all types of body
movement (mus = little mouse)
Three basic muscle types are found in the
body
Skeletal muscle
Cardiac muscle
Smooth muscle
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Skeletal Muscle Characteristics
Most are attached by tendons to bones
Cells are multinucleated
Striated – have visible banding
Voluntary – subject to conscious control
Cells are surrounded and bundled by
connective tissue
Quick, vigorous contractions but tire easily
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Connective Tissue Wrappings of Skeletal
Muscle
Endomysium – sheath
around single muscle
fiber
Perimysium – fibrous
membrane around a
fascicle (bundle) of
fibers
Figure 6.1
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Connective Tissue Wrappings of Skeletal
Muscle
Epimysium – covers
the entire skeletal
muscle (overcoat)
Fascia – on the
outside of the
epimysium
Figure 6.1
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Skeletal Muscle Attachments
Epimysium blends into a connective tissue
attachment
Tendon – cord-like structure
Aponeuroses – sheet-like structure that attaches
muscles indirectly to bones
Sites of muscle attachment
Bones
Cartilages
Connective tissue coverings
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Smooth Muscle Characteristics
Has no striations
Spindle-shaped cells
Uninucleated
Involuntary – no conscious control
Found mainly in the walls of hollow organs
Long, slow contractions
Figure 6.2a
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Cardiac Muscle Characteristics
Has striations
Uni/binucleated
Joined to another muscle cell at an intercalated disc
Involuntary
Found only in the heart
Slow, steady contractions
Figure 6.2b
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Microscopic Anatomy of Skeletal Muscle
Cells are multinucleate
Nuclei are just beneath the sarcolemma
Figure 6.3a
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Microscopic Anatomy of Skeletal Muscle
Sarcolemma – specialized plasma membrane
Sarcoplasmic reticulum – specialized smooth
ER that stores/releases Ca+
Figure 6.3a
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Figure 6.3b
Microscopic Anatomy of Skeletal Muscle
Myofibril – contractile organelles
Bundles of myofilaments (within
sarcomeres)
Myofibrils are aligned to give distinct
bands
I band =
light band
A band =
dark band
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Microscopic Anatomy of Skeletal Muscle
Sarcomere
Contractile unit of a muscle fiber
Figure 6.3b
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Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
Thick filaments = myosin filaments
Composed of the protein myosin
Has ATPase enzymes
Studded with myosin heads – cross bridges
Figure 6.3c
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Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
Thin filaments = actin filaments
Composed of the protein actin
Contain regulatory proteins to allow/prevent
binding of myosin heads
Figure 6.3c
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Microscopic Anatomy of Skeletal Muscle
Myosin filaments have heads (extensions, or
cross bridges)
At rest, there is a bare zone that lacks actin
filaments
Figure 6.3d
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Properties of Skeletal Muscle Activity
Excitability – ability to receive and respond
to a stimulus
Contractility – ability to shorten when an
adequate stimulus is received
Extensibility – ability to be stretched
Elasticity – ability to recoil and resume
resting length after being stretched
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ELAINE N. MARIEB
EIGHTH EDITION
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
The Muscular System
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Nerve Stimulus to Muscles
Skeletal muscles
must be stimulated
by a nerve to
contract
Motor unit
One neuron
Muscle cells
stimulated by
that neuron
Figure 6.4a
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Nerve Stimulus to Muscles
Neuromuscular junctions – association site of
nerve and muscle
Figure 6.5b
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Nerve Stimulus to Muscles
Synaptic cleft – gap
between nerve and
muscle
Nerve and
muscle do not
make contact
Area between
nerve and muscle
is filled with
interstitial fluid
Figure 6.5b
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Transmission of Nerve Impulse to Muscle
Neurotransmitter – chemical released by nerve upon
arrival of nerve impulse
The neurotransmitter for skeletal muscle is
acetylcholine (ACh)
Muscle contraction:
ACh diffuses across synaptic cleft
ACh attaches to receptors on the sarcolemma
When enough ACh is released, the sarcolemma
becomes permeable to sodium (Na+)
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Transmission of Nerve Impulse to Muscle
Na+ rushing into the cell (makes overly +) and upsets sarcolemma
This upset generates an action potential
Once started, muscle contraction cannot be stopped
Back to resting state by:
Diffusion of K+ out of cell
Operation of Na+/K+ pump
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The Sliding Filament Theory of Muscle
Contraction
Activation by nerve
causes myosin heads
(crossbridges) to
attach to binding sites
on the thin filament
Activated by ATP,
myosin heads then
bind to the next site of
the thin filament
Figure 6.7
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The Sliding Filament Theory of Muscle
Contraction This continued rowing
action causes a sliding of the myosin along the actin
Requires Ca++ & action potential to stimulate SR to release more Ca++ into sarcoplasm
The result is that the muscle is shortened (contracted)
Figure 6.7
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The Sliding Filament Theory of Muscle
Contraction
Meanwhile . . .
While action potential is occurring, ACh is broken down by enzymes in the sarcolemma
Single impulse means one contraction
When action potential ends Ca++ is reabsorbed into SR and muscle relaxes
WHOLE PROCESS TAKES THOUSANTHS OF A SECOND!!!
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The Sliding Filament Theory
Figure 6.8
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Contraction of a Skeletal Muscle
Muscle fiber contraction is “all or none”
Within a skeletal muscle, not all fibers may
be stimulated during the same interval
Different combinations of muscle fiber
contractions may give differing responses
Graded responses – different degrees of
skeletal muscle shortening
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Types of Graded Responses
Twitch
Single, brief contraction
Not a normal muscle function
Figure 6.9a–b
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Types of Graded Responses
Tetanus (summing of contractions)
One contraction is immediately followed
by another
The muscle does
not completely
return to a
resting state
The effects
are added
Figure 6.9a–b
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Types of Graded Responses
Unfused (incomplete) tetanus
Some relaxation occurs between
contractions
The results are summed
Figure 6.9c–d
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Types of Graded Responses
Fused (complete) tetanus
No evidence of relaxation before the
following contractions
The result is a sustained muscle
contraction
Figure 6.9c–d
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Muscle Response to Strong Stimuli
Muscle force depends upon the number of
fibers stimulated
More fibers contracting results in greater
muscle tension
Muscles can continue to contract unless they
run out of energy
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ELAINE N. MARIEB
EIGHTH EDITION
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
The Muscular System
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Energy for Muscle Contraction
Initially, muscles use stored ATP for energy
Bonds of ATP are broken to release
energy
Only 4-6 seconds worth of ATP is stored
in muscles
After this initial time, other pathways must be
utilized to produce ATP
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Energy for Muscle Contraction Direct phosphorylation
Muscle cells contain creatine phosphate (CP)
CP is a high-energy molecule
After ATP is depleted, ADP is left
CP transfers energy to ADP, to regenerate ATP
CP supplies are exhausted in about 20 seconds
Figure 6.10a
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Energy for Muscle Contraction Aerobic Respiration
Accounts for 95% of ATP used for muscular E
Series of metabolic pathways that occur in the mitochondria
Glucose is broken down to carbon dioxide and water, releasing energy
This is a slower reaction that requires continuous oxygen
Figure 6.10b
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Energy for Muscle Contraction
Anaerobic glycolysis
Reaction that breaks
down glucose without
oxygen
Glucose is broken down
to pyruvic acid to
produce some ATP
Pyruvic acid is
converted to lactic acid
Figure 6.10c
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Energy for Muscle Contraction
Anaerobic glycolysis
(continued)
This reaction is not as
efficient, but is fast
Huge amounts of
glucose are needed
Lactic acid produces
muscle fatigue
Figure 6.10c
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Muscle Fatigue and Oxygen Debt
When a muscle is fatigued, it is unable to contract
The common reason for muscle fatigue is oxygen debt
Oxygen must be “repaid” to tissue to remove oxygen debt
Oxygen is required to get rid of accumulated lactic acid
Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less
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Types of Muscle Contractions
Isotonic contractions
Myofilaments are able to slide past each
other during contractions
The muscle shortens
Isometric contractions
Tension in the muscles increases
The muscle is unable to shorten – “skids
wheels”
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Muscle Tone
Some fibers are contracted even in a relaxed muscle
Different fibers contract at different times to provide muscle tone
The process of stimulating various fibers is under involuntary control
Flaccid – soft and flabby
Atrophy – waste away
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ELAINE N. MARIEB
EIGHTH EDITION
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
The Muscular System
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Muscles and Body Movements
Movement is attained
due to a muscle
moving an attached
bone
Figure 6.12
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Muscles and Body Movements
Muscles are attached
to at least two points
Origin –
attachment to an
immoveable bone
(moves the least)
Insertion –
attachment to a
movable bone
(moves the most)
Figure 6.12
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Effects of Exercise on Muscle
Results of increased muscle use
Increase in muscle size
Increase in muscle strength
Increase in muscle efficiency
Muscle becomes more fatigue resistant
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Types of Ordinary Body Movements
Flexion
Extension
Rotation
Abduction
Adduction
Circumduction
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Body Movements
Figure 6.13a–c
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Body Movements
Figure 6.13d
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Special Movements
Dorsiflexion – flex
Plantar flexion - point
Inversion – turn sole medially
Eversion – turn sole laterally
Supination – palm up
Pronation – palm down
Opposition – “ok”
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Types of Muscles
Belly – central body of muscle
Prime mover – muscle with the major
responsibility for a certain movement
Antagonist – muscle that opposes or reverses
a prime mover
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Naming of Skeletal Muscles
Direction of muscle fibers
Example: rectus (straight)
Example: oblique (slanted)
Relative size of the muscle
Example: maximus (largest)
Example: minimus (smallest)
Example: longus (long)
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Naming of Skeletal Muscles
Location of the muscle
Example: many muscles are named for
bones (e.g., temporalis)
Number of origins
Example: biceps (two heads)
Example: triceps (three heads)
Example: quads (four heads)
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Naming of Skeletal Muscles
Location of the muscle’s origin and insertion
Example: sternocleidomastoid (sternum,
clavicle & mastoid)
Shape of the muscle
Example: deltoid (triangular)
Action of the muscle
Example: flexor and extensor (flexes or
extends a bone)
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Head and Neck Muscles
Figure 6.15
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Trunk Muscles
Figure 6.16
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Deep Trunk and Arm Muscles
Figure 6.17
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Muscles of the Pelvis, Hip, and Thigh
Figure 6.19c
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Muscles of the Lower Leg
Figure 6.20
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Superficial Muscles: Anterior
Figure 6.21
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Superficial Muscles: Posterior
Figure 6.22
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Effect of Exercise
“Use it or lose it”
Aerobic/endurance exercises – results in
stronger more flexible muscles with more
stamina
Vascularized
More mitochondria & myoglobin
Benefits whole body
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Effects of Exercise
Resistance Exercise – isometric
Increases size of muscle by making more
filaments
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Musculo-Skeletal Disorders
Rehabilitation – therapeutic exercise
Strain - tear in muscle
Sprain – overly stretched muscle
Spasm – sustained contraction
Myalgia – muscle pain
Fibromyalgia
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Musculo-Skeletal Disorders Hernia – organ protrudes through weak muscle
Abdominal
Inguinal
Hiatal
Talipes – “flat feet”
Tetanus – “lock jaw”
Torticollis – “wry neck”
Muscular Dystrophy – group of diseases where muscles deteriorate
Myasthenia Gravis – progressive muscle weakness & paralysis
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Muscular System Injuries
Lateral Epicondylitis – “tennis elbow”
Shin Splints – injury to muscle tendon on
tibia
Rotator cuff disease – inflammation of a
group of tendons that surround the pectoral
girdle