Transcript How do Muscles Work?

How do Muscles Work?

Muscles serve FOUR
functions for us:
-- motion; they move us
-- 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 slaves
roaring the oars in unison.
 Each slave had only so much
strength, but together gave the
ship’s oars incredible power.
Muscles need help…
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

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
Deep Fascia
 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
Myofibers
 Individual
muscle fibers are called
myofibers (muscle cells)
 Arranged in groups of 10-100
myofibers and these groups are
called fascicles
 Perimysium surrounds fascicles
 Endomysium surrounds individual
myofibers
Myofibrils (actin & myosin)
 Proteins
are arranged in a thread-like
appearance in the sarcoplasm
 Give skeletal and cardiac muscle
tissue their striations
muscle
cell
Skeletal Muscle Fiber Contraction
“Sliding
Filament Theory”
When muscle fibers are stimulated
to contract, myofilaments (actin an
myosin) slide past one another.
This causes sarcomeres (muscle
units) to shorten and the whole
muscle fiber shortens.
Sarcomere
Sarcomere
Sarcomere
Whole Muscle Contraction
 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.
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