Download B - Notes - Skeletal Muscle Contraction

Skeletal Muscle Contraction Notes
Review
Epimysium (outer covering of muscle)
Perimysium
(covering
fascicle)
Fascicle
(bundle of
muscle fibers)
Endomysium
(covers each
muscle fiber)
Myofibril
(bundle in
each muscle
cell – made
of actin &
myosin)
H - zone
A band
sarcomere
Which band is the thin filament?
ACTIN
Which band is the thick filament?
MYOSIN
Z - line
I band
More Interesting Muscle Facts
Your muscles are what
percentage of your body weight?
40% - 50%
What percentage of muscle is
made of water?
• SKELETAL MUSCLE
CONTRACTION
• 8 Steps
• STEP I
• an action potential travels along a
neuron to a synapse at a muscle fiber
• STEP II
• ACETYLCHOLINE (a neurotransmitter)
is released from the neuron
• STEP III
• Acetylcholine binds to muscle cell
membrane
• STEP IV
• sodium ions diffuse into the muscle
fiber, starting an action potential
• STEP V
• Calcium ions are released from
the sarcoplamic reticulum and
bind to actin
• STEP VI
• myosin attaches to actin forming
CROSS - BRIDGES
• STEP VII
• myosin pulls the actin causing it to
slide over the myosin
• STEP VIII
• ATP attaches to myosin and supplies the
energy for the myosin to pull the actin