Download The Muscular System

The Muscular System
Approximately 40% of your body weight is your
muscle.
1.
Functions
Muscles produce movement. When muscle
contracts , it pulls insertion bone near origin
bone. Movement occurs at joint between origin
and insertion.
 Origin – The bone that moves less, provides
the area of attachment for the end of the muscle
called the origin.
 Insertion – the movable bone provides the
surface for the muscle’s insertion.
e.g. biceps : origin at the joint of humerus and
scapula, insert on radius.
triceps : origin at humerus, scapula and
clavicle, inserts on ulna.
a. Biceps and triceps work in opposing pairs in an
antagonistic system.
b. Groups of muscles usually contract to produce a single
movement – synergistic pattern.
e.g. extension of lower legs is by rectus
femoris, gracilis and sartorius.
Reference: http://www.ultranet.com/~jkimball/BiologyPages/M/Muscles.html#Anatomy_of_Skeletal_Muscle
http://www.lrn.org/Content/Lessons/muscle.html#overview
2.
There are three different types of muscles
a. skeletal muscle – voluntary, striated muscle.
b. cardiac muscle – involuntary, striated
(branching) muscle.
c. smooth muscle – involuntary, non-striated
muscle, e.g. Stomach, intestinal tract, urinary
bladder and blood vessels.
Reference:
http://www.terrebonnehigh.com/science/biol2n9.htm
Skeletal Muscle Contraction
Skeletal muscles contain thousands of muscle
fibers (muscle cells). Each fiber consists of
finer threadlike structures called myofibrils.
Myofibrils contain two kinds of protein
strands: thick filament, myosin, with side
projecting cross-bridge. Thinner filament,
actin. Repeating bands of actin and myosin
translate into light – dark repeating unit that
gives skeletal muscle its striped appearance.
Dark line (Z) line between each repeating unit
is defined as sacromere that is the
fundamental unit of muscle contraction.
References:
http://www.uoguelph.ca/zoology/devobio/210labs/sketchmuscle1.html
http://www.lrn.org/Content/Lessons/muscle.html#overview
Muscle Structure
Reference:
http://members.shaw.ca/bodybuilding/Muscles/structure.html
Reference: http://www.ultranet.com/~jkimball/BiologyPages/M/Muscles.html#Anatomy_of_Skeletal_Muscle
http://www.lrn.org/Content/Lessons/muscle.html#overview
The Sliding-Filament Model
Reference: http://www.ultranet.com/~jkimball/BiologyPages/M/Muscles.html#Anatomy_of_Skeletal_Muscle
Role of Calcium in Muscle Excitation and Contraction Coupling
http://cwx.prenhall.com/bookbind/pubbooks/martinidemo/chapter10/medialib/CH10/html/ch10_4_1.html
Role of Calcium in Muscle
Excitation and Contraction

Nerve ending release neuro transmitter at neuromuscular junction – membrane excitation
 Sarcoplasmic reticulum release Ca 2+
 Ca 2+ binds to troponin removing blocking action
of tropomyosin
 Actin and myosin –cross bridge movement
 ATP is required
 Remove Ca 2+ from troponin restores blocking
action of tropomyosin
 Ca2+ uptake (ATP required)
Muscle Disorders
1.
2.
3.
4.
Muscular dystrophy – progressive weaken of
the muscles.
Paralysis – loss of ability to produce voluntary
movement. This is due to disease or injury of
brain or spinal cord or nerve
Muscle atrophy – muscle shrinkage. Decrease
in muscle size.
Muscle hypertrophy – increase in muscle size
because of over work. e.g. heart frequently
hypertrophy from over work.
Muscle Structure
Front View
Back View
Reference: http://www.rrcc.cccoes.edu/academic/health/fitnesscenter/muscle.htm