Transcript How do Muscles Work?

How do Muscles
Work?

Muscles serve FOUR
functions for us:
-- motion; they move
our skeleton
-- stability and posture
-- controlling organ
function
-- generate body heat
Characteristics of Muscle Tissue
 Excitability
– ability of the muscles to
be stimulated by nerves
 Contractility – muscles can contract
 Extensibility – muscles lengthen
 Elasticity – after shortening or
lengthening, muscle can return to its
original shape
Muscles PULL, they never push!
Roman Ship Analogy…
 Muscles
work much like an old roman
ship that used a galley of people
rowing the oars in unison.
 Each person had only so much
strength, but together, they gave the
ship’s oars incredible power.
Muscles need help…
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Muscles need to be connected
to the rest of the body
-- they need motor nerves
-- they need energy and O2
-- H20, CO2 waste & glucose
transport
Requires nerves, blood
vessels, and
the lymphatic system to carry
them
These are held in connective
tissues called
FASCIA
Muscles need to use sugar
available in blood for
energy
Fascia Galore!
 Fascia
is connective
tissue that surrounds
muscles
 Provides protection
and stability
Superficial Fascia
Closest to the skin and
holds muscle to the skin
 Also contains adipose
tissue
 Stores fat and water,
provides insulation from
heat loss, protects, and
is a place for vessels and
nerves to carry things in
and out of muscles
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Separates muscle
groups
Allows muscles to
contract without
interference from other
muscles
Each muscle has its
own outer fascia called
epimysium which is
then surrounded by
deep fascia
Deep Fascia
Superficial
Fascia
Deep Fascia
Myofibers
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Individual muscle fibers are
called myofibers (muscle
cells)
Arranged in groups of 10100 myofibers and these
groups are called fascicles
Perimysium surrounds
fascicles
Endomysium surrounds
individual myofibers
Myofibrils
 Proteins
are arranged in a thread-like
appearance within a muscle cell
 Give skeletal and cardiac muscle
tissue their striations
muscle
cell
Skeletal Muscle Fiber Contraction
“Sliding
Filament Theory”
When muscle fibers are stimulated
to contract, filaments slide past
each other getting shorter.
–Myofilaments = actin and myosin
These
filaments are arranged in
small bundles called sarcomeres
Sarcomere
Sarcomere
Sarcomere
Whole Muscle
Contraction
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The whole length of
one muscle fiber must
contract; however, the
whole muscle does not
have to contact.
The number of muscle
fibers contracting
determines the
strength of the
contraction.
Events of Sarcomere contraction
1. Electrical signals from the
brain travel through the
nervous system to the
muscle
2. Calcium is released inside
the muscle cells and binds
to troponin C causing
contraction.
3. Acitin and myosin filaments
slide past each other,
causing the muslcle to
contract
4. ATP provides chemical
energy needed for this
process.
The Effect of Exercise
A
regular exercise program will bring
about
1. Increased endurance
2. Increased strength of muscles.
 Muscle enlarge, not due to increase in
number of muscle fibers, but
increased amounts of actin and
myosin myofibrils inside each muscle
fiber making them bigger and
stronger.
 “Use it or lose it !”
Arnold….then and now!
 Exercise
increases muscle size,
strength, and endurance
– Aerobic (endurance) exercise (biking,
jogging) results in stronger, more
flexible muscles with greater resistance
to fatigue
 Makes
body metabolism more efficient
 Improves digestion, coordination
Resistance exercise like weight
lifting increases muscle size and
strength
Effect of Exercise on Muscles