1. A large number of elongated, striated,

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A.Longitudinal Section
1. A large number of elongated, striated,
multinucleated cells arranged parallel to the
long axis of the muscle. These cells are called
Muscle Fibers.
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A.Longitudinal Section
2. These fibers are only 0.01 to 0.15mm in
diameter, but range from 1 to 12cm in length.
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B.Cross Section
1. Each fiber contains a cell membrane called
the Sarcolemma.
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B.Cross Section
2. Surrounding each fiber outside the Sarcolemma
is the Endomysium.
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B.Cross Section
3. A muscle consists of bundles of these fibers
called Fasciculi.
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B.Cross Section
4. Each Fasiculus is enclosed in a connective
tissue coat called the Perimysium.
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B.Cross Section
5. Many Fasiculi form a muscle. Surrounding
each muscle is a layer of connective tissue
called the Epimysium.
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B.Cross Section
6. The Epimysium is continuous with the tendon
that attaches muscle to bone.
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B.Cross Section
7. Each Sarcolemma (muscle fiber) consists of a
number of Myofibrils.
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B.Cross Section
8. Mitochondria and the Nuclei lie near the
Myofibrils.
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B.Cross Section
8. Mitochondria and the Nuclei lie near the
Myofibrils.
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B.Cross Section
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B.Cross Section
9. Each Myofibrils consists of alternating
Light (Actin Isotropic) and Dark (Myosin
Anisotropic) bands.
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B.Cross Section
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B.Cross Section
9. Each Myofibrils consists of alternating
Light (Actin Isotropic) and Dark (Myosin
Anisotropic) bands.
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B.Cross Section
10. Light bands are made up of the Actin muscle
protein alone.
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B.Cross Section
11. The Dark bands are produced by overlapping
or weaving of the two muscles proteins Actin and
Myosin.
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B.Cross Section
12. Both muscle proteins are extremely thin with
Mysosin being much thicker than Actin.
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B.Cross Section
13. It is this Light (only Actin) and Dark
(overlapping Actin and Myosin) bands that give
Skeletal Muscle its cross stripped (striated)
appearance.
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B.Cross Section
14. Running across each I band halfway between
its two ends is a dark line called the Z
(membrane) Line. Z line to Z line is called a
Sarcomere.
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B.Cross Section
15. The M line in the middle of the A band is
where the Actin and Mysosin dont overlap.
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B.Cross Section
16. Where Actin and Mysosin overlap, they are
connected by tiny Protoplasmic Bridges which run
transversely to the long axis of the muscle.
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ATP - Power source
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Neuro-Muscular Junction
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Neuro-Muscular Junction
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Neuro-Muscular Junction
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Neuro-Muscular Junction
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Neuro-Muscular Junction
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Relaxed Muscle
1. Z lines far apart
2. H zone easy to see
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Contracting Muscle
1. Z lines closer together
2. H zone getting smaller
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Fully Contracted Muscle
1. Z lines even closer together
2. H zone not visible
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Fast Twitch
Slow Twitch
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Fast Twitch
Generates energy rapidly, quick forceful
contractions
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Slow Twitch
Generates energy over a longer time period,
fatigue resistant
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General Functions
A.Movement Skeletal Muscle Contractions produce
movements of the whole body (locomotion) or its
parts.
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General Functions
B.Heat Production Muscle cells produce heat by
the process known as catabolism
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Heat Production
General Functions
But because skeletal muscle cells are both highly
active and numerous, they produce a major share
of total body heat.
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Heat Production
General Functions
Skeletal muscle contractions are an important
part of maintaining homeostasis of temperature.
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Heat Production
General Functions
One of the main reasons women are generally
colder than men.
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General Functions
C.Posture The continued partial contraction of
many skeletal muscles makes possible standing,
sitting and other maintained positions of the
body.
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D.Atrophy Wasting away of muscle tissue
decrease in size of muscle tissue. Most likely
due to inactivity. Can occur rather quickly!
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Atrophy
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E.Hypertrophy Increase in size of muscle tissue
from an increase in size of the muscle cells.
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Hypertrophy
Occurs due to contraction of muscle cells over a
prolonged period of time. Occurs at a much
slower rate than atrophy.
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F.Dystrophy A change in muscle size or function
due to defective genetics or faulty nutrition
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Dystrophy
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Tonic Contraction
A.Tonic Contraction (tone) is a continual,
partial contraction. At any given moment a
small number of total fibers contract producing
tautness rather than a recognizable muscle
contraction.
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Tonic Contraction
Tonic contraction is characteristic of muscles of
normal individuals when they are awake.
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Tonic Contraction
It is particularly important for maintaining
posture.
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Tonic Contraction
Flaccid muscles are muscles with less tone than
normal.
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Tonic Contraction
Spastic muscles are those with more than normal
tone.
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Tonic Contraction
Special receptors in muscles permit regulation of
tone at a reflex level.
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Tonic Contraction
Example posture
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B. Isotonic Contraction
(iso, same tonic, tone or tension) is a
contraction in which the tone or tension of the
muscle remains the same but the length of the
muscle changes. It shortens producing movement
Example A pushup (movement of the arms from
triceps brachii contraction.)
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Isotonic Contraction
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Isotonic In isotonic contractions, the muscle
contracts and shortens, giving movement. Nearly
all the training you do is isotonic. Advantages St
rengthens a muscle throughout the range of
movement You can choose isotonic exercises to
match the actions in your sport
Disadvantages Can make muscles sore, because of
stress while they lengthen The muscle gains most
strength at the weakest point of the action,
rather than evenly throughout
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Concentric Contraction
A concentric contraction is a type of muscle
contraction in which the muscles shorten while
generating force.
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Eccentric Contraction
During an eccentric contraction, the muscle
elongates while under tension due to an opposing
force being greater than the force generated by
the muscle.
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Bicep Curls
Agonist Muscle
Primary Muscle Mover
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Bicep Curls
Antagonist Muscle
Muscle works in oppostion to movement
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Bicep Curls
Synergist Muscle
Muscles that help in a movement
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C. Isometric Contraction
(iso, same metric length) is a contraction
in which muscle length remains the same but in
which muscle tension increases.
Example Pushing your arms against a door jam
you can feel the tension increase in your arms
but no movement occurs.
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Isometric Contraction
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Isometric Contraction
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Isometric In isometric contractions, the muscle
contracts but does not shorten, giving no
movement. Advantages Isometric exercises develop
static strength - the strength you need to push
or pull a heavy object or hold it up They are
quick to do and don't hurt They do not need
expensive equipment You can do them anywhere
Disadvantages The muscle gains strength only at
the angle you use in the exercise During an
exercise, the blood flow to the muscle stops,
blood pressure rises, and less blood flows back
to the heart. It could be dangerous if you have
heart problems
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Isokinetic Contraction
(iso, same kinetic energy) Isokinetic
contraction causes the muscle to shorten as it
gains tension.
The difference is Isokinetic requires a constant
speed over the entire range of motion
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Isokinetic Contraction
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Isokinetic In isokinetic contractions, the muscle
contracts and shortens at constant speed. An
isotonic contraction is different to an
isokinetic contraction because it is usually
slowest at the start. For isokinetic training,
you need special equipment that detects when a
muscle is speeding up, and increases the load to
slow it down again. Advantages The muscle gains
strength evenly all through the range of movement
It is the fastest way to increase muscle
strength Disadvantage The equipment is very
expensive so most gyms cannot afford it
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D.Twitch Contraction is a quick jerky
contraction in response to a single stimulus.
The entire twitch usually lasts 1/10th of a
second. Twitch contractions rarely occur in the
body.
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E.Tetanic Contraction is a more sustained
contraction than a twitch. Normal movements are
produced by incomplete tetanic contractions.
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F.Treppe (staircase phenomenon) is an event in
which increasingly stronger twitch contractions
occur in response to constant-strength stimuli.

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Treppe
In other words a muscle contracts more forcefully
after it has contracted a few times than when it
firsts contracts.
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Treppe
If continued maximal contractions occur, the
muscle in time lessens its irritability and
contractility and may result in muscle fatigue.
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Treppe
Example why does an athlete warm up / but not
for a hour
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G.Fibrillation is an abnormal contraction in
which individual fibers contract asynchronously,
producing a flutter of a muscle but no effective
movement.
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Example Fibrillation of the heart occurs fairly
often and is a frequent cause of death you
would use a defibrillator.
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H.Convulsions Are abnormal uncoordinated titanic
contractions of varying groups of muscles
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Muscle Tone
1.During Strenuous exercise all the fibers in a
muscle DO NOT Contract
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Muscle Tone
2.During Rest a small percentage of cells are in
a state of contraction
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Muscle Tone
3.Age or poor health will cause a person to lose
much of their muscle tone
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Muscle Tone
4.At rest relatively few muscles are active at
any given time
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Muscle Tone
5.When stress is placed on a muscle more and
more fibers are brought into play this is
called RECRUITMENT.
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A.Electric Shock
Muscle Response 1.Muscles cells respond to a
number of stimuli
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B.Change in Temperature
Muscle Response 1.Muscles cells respond to a
number of stimuli
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C.Change in PH
Muscle Response 1.Muscles cells respond to a
number of stimuli
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D.Change in Ionic Concentration
Muscle Response 1.Muscles cells respond to a
number of stimuli
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E.Change in Certain Chemicals
Muscle Response 1.Muscles cells respond to a
number of stimuli
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A.Subthreshold too weak to bring about a
response
Muscle Response 2.Classification of electrical
stimuli
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B.Threshold one or more fibers will respond
Muscle Response 2.Classification of electrical
stimuli
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C.Maximal brings a maximal response to a whole
muscle
Muscle Response 2.Classification of electrical
stimuli