Muscles are made up of fibers that contain smaller
bundles, called sarcomeres, connected end to end.
These bundles of cells are wrapped in a thin skin called
perimysium. All muscles have these bundles; in fact,
the bigger the muscle, the more bundles inside.
Muscles operate by contracting. During the
contraction, the ends of each sarcomere pull toward
each other. After the contraction, the sarcomeres are
shorter. This simple pulling action is responsible
for many of your movements.
Let’s take a closer look at the action within the sarcomeres.
Sarcomeres contain two types of protein: myosin and actin.
Myosin is a thin protein with a head on it, like a pushpin. Within
a sarcomere, myosin proteins are bundled together with the heads
pointing out; picture a bundle of flowers joined at the base
of the stems.
The actin protein is round, like a ball. These balls are linked
together like beads of a necklace to create a long filament. The
myosin and actin are arranged in alternating rows in order for
the sarcomeres to contract. The myosin heads connect to the
actin and pull them inward, which is why the length of the
muscle fiber is shortened when the muscles are contracted.
Howmuscles
work
Working in pairs
When the biceps muscle
contracts, it pulls your
forearm and bends your arm.
When the
triceps muscle
contracts, it straightens
your arm.
Your forearm
contains pairs of
muscles that move
your hand and fingers
back and forth.
Sources
background-information-for-teachers-and-parents/?bp-jr-topic=muscles
/
quadriceps_animation.shtml
/
circulatory-and-respiratory-systems/skeletal-and-muscular-systems
-
background-information-for-teachers-and-parents/?bp-jr-topic=bones
Bones%20Bones%20Exploring%20the%20Skeletal%20System.pdf
Bones%20Exploring%20the%20Skeletal%20System.pdf
/
Strengthen and
protect your muscles
Just as strength training and aerobic exercise help your bones
and joints stay strong, regular exercise is very important for
healthy muscles, too. Aerobic exercise, which gets your heart
pumping, not only keeps your heart muscles strong, but
also works muscles throughout your body.
Which of the muscles you learned about are hard at work
when you’re swimming, running or dancing? How are these
movements different from each other?
Each one of your hands has 27 bones.
Some people
call the humerus bone
the“funny bone”because
it sounds like“humorous.”
But when you bump
your elbow, you
won’t think
it’s so funny.
