Download Muscles move skeletal parts by contracting

MUSCLES MOVE SKELETAL PARTS BY
CONTRACTING
Team 1
CONTRACTIONS
The ability to move requires that the muscles
be attached to the skeleton in antagonistic
pairs
 When bicep contracts, triceps relax- When
triceps contract, biceps relax

THE STRUCTURE OF SKELETAL MUSCLE

Muscle fiber consists of a bundle of long fibers
running parallel to the length of the muscle
 Bundle
of myofibrils arranged longitudinally
MYOFIBRILS

Two kinds of myofilaments :
 Thin
filaments- two strands of actin and one strand
of regulatory protein coiled around thick filament
 Thick filaments- staggered array of myosin
CONTRACTIONS



In a relaxed muscle fiber, the I bands and the H zone
are relatively wide
During contraction, the thick, and thin filaments slide
past each other, reducing the width of the I bands and
H zone and shortening the sacromere
In a fully contracted muscle fiber, the thin filaments
overlap, eliminating the H zone. The I bands disappear
as the ends of the thick filaments contract the Z lines

Myosin-Actin interactions underlying
muscle fiber contraction
 See
figure 49.30, page 1068 as we explain