Download muscle and muscle action

INTRODUCTION
Humans have over 650 muscles which differ in
size according to the jobs they do.
These muscles constitute 40% of our body
weight.
The special function of muscle tissue is
contraction.
CONTRACTION: a shortening or tensing of a
part or organ (especially of a muscle or
muscle fiber)
TYPES OF MUSCLE
VOLUNTARY/SKELETAL MUSCLE
INVOLUNTARY MUSCLE
CARDIAC MUSCLE
VOLUNTARY/SKELETAL MUSCLE
Muscle that is under the control of the will and is
generally attached to the skeleton
Fast acting, Powerful, Eventually will tire
FOR EXAMPLE: Biceps and Deltoids
INVOLUNTARY MUSCLE
Muscle whose activity is not under the control of the will;
it is supplied by the autonomic nervous system -The
part of the vertebrate that supplies stimulation via
motor nerves to the smooth and cardiac muscles (the
involuntary muscles) and to the glands of the body
Slow acting
We do not have conscious control
Weak.
FOR EXAMPLE: Muscles of Digestive Tract/Bladder
CARDIAC MUSCLE
A type of muscle with unique features only found in the
heart. The cardiac muscle is the muscle of the heart
and medically is called the myocardium.
Own blood supply
Does not tire
Fast acting
Powerful
FUNCTIONING OF A MUSCLE
Muscle has only one function and that is to contract.
Muscles are attached to bones by tendons so when a
muscle contracts it pulls on the bones that it is
attached to and the result is movement of that bone.
The type of movement is determined by the joint at
which the bone occurs.
Because a muscle can only contract it can not move
the bone back to its original position, i.e. it can not
relax. So muscles usually work in pairs of opposites
(Antagonistic pairs).
FUNCTIONING OF A MUSCLE
(continued)
Although muscles are known individually by the
particular anatomical name, they are also known
collectively by the type of movement that their
contraction creates.
E.g. When the biceps contracts it bends the arm and
pulls the hand up towards the shoulder. The
movement that has occurred is flexion at the elbow.
– So the biceps is known as a “Flexor” muscle.
The opposite movement is extension and the triceps is
known as an “Extensor” muscle
MUSCLE ATTACHMENT
Muscles are attached to bones by tendons.
Tendons are fibrous straps that grow out of
the bone and into the muscle. They are very
strong and elastic, indeed the Achilles tendon
is the strongest thing in the body.
ORIGIN AND INSERTION
A muscle is attached to at least two bones.
These two attachments are different and are known
by different names:
ORIGIN and INSERTION
The origin is the point of attachment for the muscle to
the bone that it is anchored to.
The point of insertion is the point of attachment for the
muscle to the bone that it moves.
EX: The point of origin for the Biceps is the Scapula
and the point of insertion is the radius i.e. it does not
move the scapula but it does move the radius.
DIFFERENT ROLES OF MUSCLE
Different muscles perform different
functions…sometimes at different times
AGONIST (Prime Mover)
This is the muscle whose contraction
and subsequent pull on the insertion
tendon creates the movement
EX: the hamstrings when bending the
leg to run.
ANTAGONIST
This is the muscle that is relatively
passive during the movement, but that
will become the prime mover when the
body part is returned to its original
position
EX: the quadriceps during the first part
of the stride when running.
SYNERGIST
This is the muscle that helps to stabilize
the body part that is being moved.
It is adjacent to the insertion tendon.
EX: around the elbow during the bicep
curl
(Biceps is the agonist, Triceps is
antagonist).
FIXATOR
This is the muscle that provides stability
at the point of origin for the working
muscle, EX: The muscles of the shoulder and
upper back during the bicep curl.
TYPES OF MUSCLE FIBER
Muscle Fiber can be either:
SLOW TWITCH – (Type 1)
Endurance Fiber, works well with oxygen,
aerobic Ex: Long Distance Runners
FAST TWITCH – (Type 2)
Power Fiber, Quick Bursts
anaerobic Ex. Sprinters, Power Lifters
Slow-Twitch
Slow-twitch fibres contract slowly
and can be used for longer periods
of time. Postural muscle of the back
are composed of mostly slow-twitch
muscle fibers. Athletes who run long
distances need more slow-twitch
fibers in their legs. Slow-twitch
muscle fibers rely on oxygen as
their main energy source.
Fast-Twitch
Fast-twitch fibers contract quickly and
provide strength and speed, though they
also fatigue more quickly. Sprinters
require short but intense bursts of
energy and therefore need more fasttwitch muscle fibers. Fast-twitch muscle
fibers rely on ATP and glycogen as their
main energy source. As ATP sources
can be rapidly depleted, lactic acid is a
by product of the breakdown of
glycogen, fast-twitch fibers can only be
active for a short period of time.
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