Download Muscles PPT

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Types of Muscle
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The human body is comprised of 324 muscles
Muscle makes up 30-35% (in women) and 42-47% (in men) of body
mass.
Three types of muscle:
Skeletal muscle
Cardiac muscle
Smooth muscle
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A. Skeletal (Striated) Muscle
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Connects the various parts of the skeleton through one or more
connective tissue tendons
During muscle contraction, skeletal muscle shortens and moves
various parts of the skeleton
Activated through signals carried to the muscles via nerves (voluntary
control)
Repeated activation of a skeletal muscle can lead to fatigue
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B. Smooth Muscle
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Located in the blood vessels, the
respiratory tract, the iris of the eye,
the gastro-intestinal tract
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The contractions are slow and
uniform
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Activation is involuntary
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C. Cardiac Muscle
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Has characteristics of both
skeletal and smooth muscle
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Functions to provide the
contractile activity of the heart
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Is very fatigue resistant
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Activation of cardiac muscle is
involuntary (like smooth muscle)
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Components of skeletal muscle
d) myofibril
c) muscle fibre
b) muscle fibre bundle a) Muscle belly
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Muscle Fibres
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Each fibre is made up of a number of myofilaments
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Surrounded by a connective tissue sheath called
Sarcolemma
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Many fibres are enclosed by connective tissue sheath
Perimycium to form bundle of fibres
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Group of fibres activated via same nerve: motor unit
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Each fibre has capillaries that supply nutrients and
eliminate waste
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Muscle Teamwork
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Agonist (prime mover):
- the muscle or group of muscles producing a desired effect
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Antagonist:
- the muscle or group of muscles opposing the action
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Synergist:
- the muscles surrounding the joint being moved
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Fixators:
- the muscle or group of muscles that steady joints closer to the body axis so
that the desired action can occur
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Bending or straightening of elbow requires the coordinated
interplay of the biceps and triceps muscles
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Contractile Machinery:
Sarcomeres
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Contractile units
Organized in series ( attached
end to end)
Two types of protein
myofilaments:
- Actin:
thin filament
- Myosin: thick filament
Each myosin is surrounded by
six actin filaments
Projecting from each myosin
are tiny contractile myosin
bridges
Longitudinal section of myofibril
a) at rest
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Contractile Machinery:
Crossbridge formation and movement
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Cross bridge formation:
- a signal comes from the motor
nerve activating the fibre
- the heads of the myosin filaments
temporarily attach themselves to the
actin filaments
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Cross bridge movement:
- similar to the stroking of the oars and
movement of rowing shell
- movement of myosin filaments in relation
to actin filaments
- shortening of the sarcomere
- shortening of each sarcomere is additive
Longitudinal section of myofibril
b) contraction
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Contractile Machinery:
Optimal Crossbridge formation
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Sarcomeres should be
optimal distance apart
If the sarcomeres are
stretched farther apart than
optimal distance:
- fewer cross bridges can
form  less force produced
If the sarcomeres are too
close together:
- cross bridges interfere
with one another as they
form  less force produced
Longitudinal section of myofibril
c) Powerful stretching
d) Powerful contraction
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Contractile Machinery:
Optimal muscle length and optimal joint angle
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The distance between sarcomeres is dependent on the stretch of
the muscle and the position of the joint
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Maximal muscle force occurs at optimal muscle length (lo)
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Maximal muscle force occurs at optimal joint angle
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Optimal joint angle occurs at optimal muscle length
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Muscle tension during elbow flexion at constant speed
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Contractile Machinery:
Tendons, origin, insertion
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In order for muscles to contract, they must be
attached to the bones to create movement
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Tendons: strong fibrous tissues at the ends of
each muscle that attach muscle to bone
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Origin:
the end of the muscle attached to the
bone that does not move
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Insertion: the point of attachment of the muscle
on the bone that moves
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Muscle Fibre Types
Slow twitch fibres:
Slow Oxidative (Type I)
Fast twitch fibres:
Fast Glycolytic (Type IIb)
Fast Oxidative Glyc. (Type IIb)
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A. Slow Twitch Fibres
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Suited for repeated contractions during activities requiring a
force output of < 20-25% of max force output
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Examples: lower power activities, endurance events
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B) Fast Twitch Fibres
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Significantly greater force and speed generating capability than
slow twitch fibres
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Well suited for activities involving high power
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Examples: sprinting, jumping, throwing
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The Muscle Biopsy
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Used to determine muscle fibre type
1. Injection of local anesthetic into the muscle being sampled
2. Incision of approximately 5-7mm is made in the skin and fascia
of the muscle
3. The piece of tissue (250-300mg) removed via the biopsy needle
is imbedded in OCT compound
4. The sample is frozen in isopentane cooled to –180C
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Nerve-Muscle Interaction
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Skeletal muscle activation is initiated through neural activation
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NS can be divided into central (CNS) and peripheral (PNS)
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The NS can be divided in terms of function: motor and sensory
activity
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Sensory: collects info from the various sensors located
throughout the body and transmits the info to the brain
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Motor: conducts signals to activate muscle contraction
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Activation of motor unit and its innervation systems
1. Spinal cord 2. Cytosome
3. Spinal nerve
4. Motor nerve 5. Sensory nerve 6. Muscle with muscle fibres
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Motor Unit
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Motor nerves extend from the spinal cord to the muscle
fibres
Each fibre is activated through impulses delivered via
motor end plate
Motor unit: a group of fibres activated via the same nerve
Muscles needed to perform precise movements generally
consist of a large number of motor units and few muscle
fibres
Less precise movements are carried out by muscles
composed of fewer motor units with many fibres per unit
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Muscle’s Adaptation to Strength Training
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Individual’s performance improvements occur through a
process of biological adaptation, which is reflected in the
body’s increased strength
Adaptation process proceeds at different time rates for
different functional systems and physiological processes
Adaptation depends on intensity levels used in training and
on athlete’s unique biological make-up
Enzymes adapt within hours, cardiovascular adaptation
within 10 to 14 days
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