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Physiology Review
(ppt modified from http://www.recreation.ucsb.edu/ess/ess40/chap8.htm)
The
SARCOMERE
is the
functional unit
of the muscle.
A sarcomere is
found between
two Z lines.
The Muscle Fiber Is Composed
of Special Contractile Proteins
• Myosin is the main, thick structural
protein in the sarcomere. It has cross
bridges for attaching to the Actin
protein.
• Actin is the main, thin structural
protein in the sarcomere. Each actin
molecule has a binding site that can
attach with a Myosin cross bridge.
• Actin and myosin are contractile
proteins.
Tropomyosin and Troponin Are
Regulatory Proteins.
These regulatory proteins
control the muscle contraction
process.
• They either allow or block
actin-myosin interaction
depending on their
configuration.
TROPOMYOSIN
• Tropomyosin covers the
actin binding sites.
• This prevents the union of
actin with myosin cross
bridges.
TROPONIN
• Troponin has three binding sites:
– one binds to Tropomyosin, one to
Actin, and one to Ca+ ions.
– When calcium combines with troponin,
tropomyosin slips away from its
blocking position between actin and
myosin.
– With this change actin and myosin can
interact and muscle contraction can
occur.
•
fig.cox.miami.edu/.../150/neuro/tropomyosin.jpg
Sliding Filament Mechanism
• The myosin cross bridges can
bind to the actin.
• After binding the thin (actin)
filaments are pulled toward the
center of the sarcomere.
• This is known as the Sliding
Filament Mechanism.
•
http://people.eku.edu/ritchisong/crossbridge3.gif
SLIDING FILAMENT
MECHANISM
• Neither the thick nor thin
filaments change in length.
They change their position
with one another.
• The actin slides closer
together between the thick
filaments.
•
http://3dotstudio.com/contract.gif
• The myosin cross bridges pull the thin
actin filaments inward.
• A single power stroke pulls the actin
inward only a small percentage of the total
distance.
• Complete shortening occurs by repeated
cycles of the power stroke.
• The link between myosin and actin is
broken at the end of one cross bridge
cycle. A cross bridge returns to its original
position and can connect to the next actin
molecule position, pulling the actin
filament further.
www.octc.kctcs.edu
Muscle contraction
• The process starts when the muscle cell is
depolarized
• A neuron sends action potentials to muscle fibers.
• This neuron releases acetylcholine at the
neuromuscular junction.
• This produces an action potential over the entire
muscle cell membrane.
– Sodium/Potassium pumps are not working when Ach is
on the receptors of muscle cells…chaos ensues!
The Release of Calcium Ions from the
sacroplasmic reticulum starts the Sliding
Process.
• Calcium from the SR binds with troponin.
• By this event, tropomyosin is pulled off the
binding sites of actin
• This allows the myosin cross bridges to
bind to actin and slide this protein.
Test Information…
• 60 points total
–20 Anatomy ID—real people,
pictures and microscope slides
–Some anatomy on Physiology
portion
• Body movements
• Draw a line drawing of sarcomere
Name this muscle
Muscle?
Muscle?
Notecardable items…
• Fill in the blank (with words
provided) of body movements (4)
• Two short answers have choices…choose
the question you can answer the MOST
completely.
– A diagnostic vs. muscle connections
– Mitochondria’s role in contraction vs
blood supply
Short Answer Questions
(notecardable…)
• Explain the protein alignment
within a sarcomere. Draw a
diagram as well…
Short Answer Questions
(notecardable…)
• Physiology of muscle cell—
broken into 5 questions
– Three phases of function of MC
– Function of neuromuscular
junction
– Stimulation in detail
– Contraction in detail
– Mechanism for lengthening
Short Answer Questions
(notecardable…)
• Antagonistic/Synergistic as it relates
to function of muscles
• Difference between strains, sprains
and contusions
• Three factors contributing to muscle
aging
• Steroid question—what have you
learned about the pros/cons/debate?