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What types of cells are found in muscle tissue?
How are these cells specialized to carry out their
function?
What does BMI measure?
FUNCTIONS

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Pumping blood
throughout the
body
Moving the skeletal
system
Passing food
through the
digestive system
CONTRACTILE CELLS
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Specialized cell membrane
and cytoskeleton that
permit them to change
their shape
Cytoskeleton allows
shortening in one or more
planes (contraction)
Laid out as sheets of
muscle tissue that produce
coordinated contractions
High energy
needs
Glucose
Blood Supply
Electrolytes
Oxygen
Remove
metabolic
wastes
calcium
From bones
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Compares the amount of muscle mass with the
body fat composition.
A certain degree of leanness is known to reduce
heart disease and metabolic disorders.
Contractile proteins:
of the
VoluntaryProteins
or
cytoskeleton involved
in contraction
Involuntary
(shortening) of muscle cells
Appearance
Location
Uniform arrangement of
contractile proteins
Can see microscopically
Stronger Contractions
Randomized pattern of
contractile proteins
Cannot see
microscopically
Weaker contractions
Voluntary

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Large degree of control
Some unconsciously
(breathing)
Some contractions are
intentional
Involuntary

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Contract without
conscious control
Jobs that are automatic
or in conjunction with
other organ systems
Cardiac
Make up the heart
Striated
Connected by
intercalated disks
Involuntary
Skeletal
Smooth
Large cells with
distinct striations
Spindle or
teardrop cells
Strong directional
contractions
Fibers not visible
Attach to bones
and joints that
produces body
movement
Most are
voluntary
Weak
contractions that
last a long time
Linings of BVs
Tubular organs
Most involuntary
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Briefly describe myogenesis.
Briefly characterize the three types of muscle cells
How do contractile proteins contribute to skeletal
function?
Why is the “intrinsic beat” of cardiac muscle cells
significant?
Why is “peristalsis” significant?
Describe the relationship between muscle cells and
muscle fibers
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Muscle develops in mesoderm cells: myogenesis
Stem cells form myoblasts
Myoblasts move to other developing tissues to form the 3
muscle types
 Growth factors (chemicals that act as signals to initiate
cell division & differentiation) by tissues give direction as
to what type of muscle needs to form.

Cardiac
•Form around large BV
and form heart
•Strong contractions
•Not conscious control
•Have 2 nuclei per cell
•Cells are branched
•Communicate thru
intercalated disks
•Intrinsic beat: all cardiac
cells act in unison,
coordinated thru
intercalated disks
Skeletal
•Provides movement
•Large cells with
distinct striations
•Powerful contractile
capabilities
•One cell is composed
of several myoblasts
that fuse into a muscle
fiber—why so many
nuclei?
•Each fiber stimulated
by a motor nerve cell
that controls several
muscle fibers at once
Smooth
• Lining of BV, digestive
organs, urinary system,
respiratory system
•Nonstriated
•Weak involuntary
contractions can last
for a long time
•Dilation and
constriction of BV and
tubular structures in
respiratory system
•Peristalsis: laid in
sheets in digestive
system. Moves food &
wastes through
Cardiac Muscle: Branching, striated cells
fused at plasma membranes.
Skeletal Muscle: Long, striated cells with
multiple nuclei
Smooth Muscle: Long, spindleshaped cells each with a single
nucleus
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How do contractile proteins contribute to skeletal
function?
Why is the “intrinsic beat” of cardiac muscle cells
significant?
Why is “peristalsis” significant?
Describe the relationship between muscle cells and
muscle fibers
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Describe the basic structure of skeletal muscle cells
Briefly summarize the various types of fibers found
in a muscle cell
Describe the relationship between myofibrils,
muscle fibers, and fasciculi
Why is a sarcomere called the “contractile unit” of
the muscle?
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Skeletal muscle fibers
located in muscles
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Entire muscle surrounded
by epimysium, a CT
layer
Subdivided into fiber
bundles called fascicles
(fasciculi)
Fascilcles surrounded by
perimysium, also CT
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Portions of perimysium
extend into the
endomysium
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Thin layer of CT that
covers each muscle fiber
Muscle fiber (bundle)=
multinucleate cell
Actin
Myosin
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Sarcomere= basic (functional)
contractile unit
Separated by each other by dark Z
lines/discs
 Actin & myosin slide past each
other as the muscle contracts
 Contraction requires Ca2+ and ATP

Sarcomere
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Z-line/disc – vertical protein bands that hold
sarcomere to sarcolemma.
I Bands
 Lighter areas of non-overlap between actin and myosin
 Contain the Z-lines.
Dark Bands = A Bands
 Areas where some overlap occurs
 = “Striations” on the slide
 Coincide with the length of myosin myofilaments.
 H-zone – light area within A-band
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Each myofibril is surrounded by network of tubes
and storage sacs (Transverse tubules and
sarcoplasmic reticulum)
Releases Ca2+ ions when stimulated by motor
neuron
Triggers contraction (more on this later…)
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Muscle FIBERS: grouped into
bundles (fasciculi)
= 1 cell!
Fibers contain myofibrils
with:

ACTIN: thin myofilaments
 Also contain:
 Tropomyosin
 Troponin
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MYOSIN: thick myofilaments,
with “swiveling” arm and head
TITIN: elastic fibers that hold
myosin in place, controlling
stretch of sarcomere
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How would a muscle appear to change microscopically
during a contraction?
What are the three stages of muscle contraction?
What is the role of neurotransmitters during muscle
contraction?
Describe the ion concentrations found inside and outside a
resting muscle cell
Briefly describe the events that occur during the muscle
contraction phase.
What is the role of ATP during this phase?
What must occur for a muscle cell to “fully” recover after a
contraction?
What occurs during “rigor mortis”?
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Sarcomeres shorten, distance between z-lines
reduced
Thick and thin myofilaments overlap more during
contraction
3 stages:
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Neural stimulation
Muscle cell contraction
Muscle cell relaxation
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Stimulation of a muscle by a nerve impulse (motor
nerve) is required before a muscle can shorten
Neuromuscular junction: point of contact b/w
nerve ending and the muscle fiber it innervates.
Motor unit: motor neuron + muscle cell
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Motor neuron releases neurotransmitters to
stimulate a contraction
Acetylcholine (Ach) binds to receptors located on
sarcolemma
 Changes transport proteins found in sarcolemma
 Alters transport of ions

 Normally, more Sodium (Na+) ions outside muscle cell,
while Potassium (K+) higher inside
 Sodium/Potassium pumps maintain this unequal
concentration
  Excitable condition
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When stimulated, ion channels open, depolarizing
the cell
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Na+ flows in, K+ out
 sarcoplasmic reticulum releases stored calcium
 Ca2+ travels to sarcomere, initiating muscle contraction
phase
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Click here to view animation
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In the absence of Calcium
Tropomyosin
ions…

Troponin “hat” sits on
Tropomyosin filament
 These blocks access to
the myosin head’s
binding site on actin.
Troponin
Ca2+
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When Calcium is released by the Sarcoplasmic
reticulum
 it diffuses into the muscles
 binds to the troponin “hat”
 shifting both the troponin and tropomyosin filament
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Myosin splits ATP and undergoes a conformational
change into a high-energy state.
The head of myosin binds to actin
 Forms a cross-bridge between the thick and thin
filaments.
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The energy stored by myosin is released
 ADP and phosphate released from myosin.
The myosin molecule relaxes
 Causes rotation of the globular head
 This leads to the sliding of the filaments.
This cycle continues until Ca2+ ions gone (and
stimulus stops)
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ATP binds to cross bridge, causing cross bridge to
disconnect from actin.
Splitting of ATP leads to re-energizing/ repositioning
of the cross bridge.
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Complete contraction of muscle cell requires
several cycles of neural stimulation and contraction
phases
Ca2+ ions transported back to sarcoplasmic
reticulum (req. ATP)
When the calcium level decreases
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troponin locks tropomyosin back into the blocking
position
thin filament (actin) slides back to the resting state (when
ATP binds to myosin head)
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Relaxation phase occurs when no more neural
stimulations are exciting the sarcolemma
 Na+/K+ pump returns ions to resting state
 Muscle cell remains in contracted, but pliable
state
 Must be “stretched” back into position
1.
2.
3.
ATP transfers its energy to the myosin cross
bridge, which in turn energizes the power stroke.
ATP disconnects the myosin cross bridge from the
binding site on actin.
ATP fuels the pump that actively transports
calcium ions back into the sarcoplasmic reticulum.
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In death…
Calcium leaks out of sarcoplasmic reticulum into
sarcomere
Causes muscle tension = rigor mortis
 Muscle cell structures start breaking down, causing
muscle to loosen (unless body becomes dehydrated)
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Stores energy in muscle cells
Collects energy from ATP, stores for long periods of
time

Transfers back to ATP when needed
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Stored form of glucose
Energy reserve for muscle action
Continuous supply needed to produce ATP
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Red pigment that stores oxygen for muscle cells
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“Grabs” oxygen from hemoglobin in blood
High affinity for oxygen
Allows cells to produce large amounts of ATP
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What determines a muscle’s morphology?
Distinguish between a muscle’s origin and insertion
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Review the location of the various gross skeletal
muscle types listed on page. 231
List, and briefly describe, the various terms that
describe the muscle structures, patterns, and shapes
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Parallel
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general-purpose muscles
Sheets of muscle cells that run in the same direction
Contractions for moving light loads over a long distance
Pinnate
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Feather-pattern
Great strength for moving heavy loads over a short
distance
Strong movements for the arms and legs
Muscle group
Shape
Function
Deltoid
Triangular
Pulling power
Trapezius
Trapezoid
Pulling power
Rhomboideus
Diamond
Holding power for scapulae
Serratus
Saw-toothed
Short movements of the arms, rib cage, and
shoulders
Biceps
2 heads
Upper arms
Triceps
3 heads
Upper arms
Quadriceps
4 heads
Upper legs
Size
Description
Maximus
Largest muscle in the group
Minimus
Smallest muscle in the group
Longus
Longest muscle in the group (arms and legs)
Brevis
Shortest muscle in the group (arms and legs)
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In words, briefly review the basic structure of a
skeletal muscle
What occurs to a muscle during atrophy?
Hypertrophy?
A
B
C
D(membrane)
E(fluid in cells)
F
H
G
F
C
E
D
C
F
E
A (blue line)
B (Red line)
E
A (blue line)
B (Red line)
C
G
G
C
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Atrophy
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Lose sarcomere proteins
 Causes muscle shrinkage
 Loss of contraction strength & size
 Can happen with a lack of neural stimulation
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Hypertrophy
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Regular use causes increased blood flow
Increase in muscle diameter and thus muscle strength
Genetic differences / variation in blood flow may cause an
increase in sarcomere density without increase in muscle
size
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How are “graded effects” accomplished during a
muscle contraction?
Differentiate between strength and endurance.
What is an antagonistic effect? Why are these
essential to normal muscle function?
List and briefly describe the various categories of
muscle action.
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Origin – point of attachment of a muscle that
remains fixed during contraction
Insertion – point of attachment of a muscle
connected to movable component on other end
Shortening/contraction = moves insertion closer to
origin
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All muscle fibers contract with a particular strength
when threshold neural stimulation reached
How are muscles able to perform at different
“powers”?

Graded effects can be accomplished by:
 Contracting more fascicles = more strength
 Muscles working together

Endurance = producing contracting and relaxing fascicle
groups
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Strength = ability to do more work
Endurance = longer period of work
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One muscle opposes or resists the action of
another
Weakens muscle strength
Gravity can have antagonistic effect
Essential!
Pulls relaxed muscles back to original strength
 Cartilage can do this (in ribcage during breathing)
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Synergism = muscles work together
Muscle
Action
Movement
Antagonistic Toward….
Abductor
Away from midline
Adductors
Adductor
Toward the midline
Abductors
Depressor
Downward movement
Levator
Extensor
Increase angle of joint
Flexor
Flexor
Decrease angle of joint
Extensor
Levator
Upward movement
Depressor
Pronator
Turn palm down
Supinator
Rotator
Turn along longitudinal axis
None
Sphincter
Decrease size of opening
None-attached to skin or connective
tissue
Supinator
Turn palm up
Pronator
Tensor
Posture, make body part
more rigid, tense
Many
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Another way to define muscle
action
Isotonic: muscle is actively
shortening or lengthening.
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Lifting/lowering weights
Isometric: muscle remains steady
in length, undergoing
indistinguishable pulses of
shortening and lengthening

Pushing against something too
heavy to move
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Differentiate between muscle strains and sprains
Differentiate between spasms and cramps of
muscles
How are rigid and flaccid paralysis different?
What causes tetanus?
Review the various myopathies listed on p. 242.
Make a chart/concept map to summarize the major
characteristics of each.
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What can cause cachexia?
Why do muscles require a high protein turnover?
What is the role of IGF-1 in muscle health?