Skeletal muscle
-Made of fascicles made of muscle fibers. Muscle fibers are
multinucleated induvial muscle cells. Myofibrils are
comprised of myofilaments composed of sarcomeres.
-H zone (helle zone) is spilt down the middle by M line. H
zone disappears as the sarcomere contracts and actin does
not overlap myosin. I bands (isotropic band) are spilt down
the middle by Z discs.
-Thick filaments contain myosin and extend across the A
band (anisotropic band) connected at the M line. Myosin is a
large molecule that has a tail region named light
meromyosin and headgroups named heavy meromyosin.
The tail and head region connect to actin.
-Thin filaments contain actin extending across the I band and
into the A band.
-Titin, a protein involved in sarcomere organization, are
elastic filaments spanning from the Z disc to the thick
filament involved in storing energy. They help increase the
total tension in filaments.
-Heads are site of activity because of ATP and actin binding
sites for cross bridges
-Creatine phosphokinase is a type of protein found in the
sarcomere for energy metabolism. This converts ADP to ATP
for muscle contraction.
-Sarcoplasmic reticulum: surround microfibrils to regulate
calcium storage and calcium includes t tubules.
Sliding filament model
-When nervous system stimulates muscle fibers, myosin
heads interact with binding sites on actin. Thick and thin
filaments pull z disc towards mline. I bands shorten and H
band disappears. A bands get closer together which
produces a muscle contraction
-The muscle contracts when myosin and actin glide over each
other shortening the muscle. Z lines come together towards
the sarcomere.
Cross bridge cycle
-Four steps are involved in the cross-bridge cycle. The first of
them being the crossbridge attachment. Energized myosin
