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basic unit of contraction
sarcomere
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what extends from z-line to z-line
sarcomere
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involved in turning contraction on and off
regulatory proteins
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what causes sarcomere to contract?
reaction of actin and myosin
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repeated unit of thick and thin that gives you the striations
myofilaments
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has actin and regulatory proteins
thin myofilaments
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has myosin
thick myofilaments
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3 thin filaments?
- actin monomer
- actin polymer
- regulatory proteins
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shape of actin monomer?
globular
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yellow disk or circle where actin interacts with myosin
binding sites
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actin monomers patched together to form a string
actin polymer
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use 2 of these strings to make thin filaments
actin polymer
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with actin polymers, why is rotation important?
binding sites can face in all different directions
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2 types of regulatory proteins?
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sits on top of binding sites
tropomyosin
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found along tropomyosin and is a molecule that interacts with calcium ion
troponin
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what happens if binding sites are blocked?
sarcomere cannot contract
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2 shapes of troponin and tropomyosin?
either blocks or exposes binding sites
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once binding sites are exposed what happens?
contraction is automatic
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how to control contraction?
by controlling myosin access to binding sites
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stalk of myosin?
linear end
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head of myosin monomer?
globular end
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crossbridge of myosin monomer?
attachment of head to actin
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high energy form?
cocked position of myosin
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low energy form
rotator position of myosin
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from high to end, myosin monomer: ___ rotates towards ___
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heads face both directions
myosin polymer
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thick filaments grab thin on both sides and pull in
contraction
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what happens during the resting state?
- no myosin-actin building
- tropomyosin blocking binding sites on actin
- calcium is stored in sarcoplasmic recticulum
- all myosin heads are in cocked position
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initiation of contraction?
stimulation
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message relaying down?
action potential
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during the resting state there is no?
contraction
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stimulation is associated with?
neural impulse
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during stimulation what happens?
neural action potential arrives at muscle fiber
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during stimulation, the muscle fiber conducts
the action potential
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during stimulation, the sarcoplasmic recticulum
releases calcium into the cell, then the calcium binds to tropomin
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when exposing binding states you?
change shapes
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what happens when binding sites are exposed?
binding of calcium to troponin
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binding of calcium to troponin cause a conformational change in troponin
tropomyosin complex
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____ rotates, thereby exposing myosin binding sites on action
tropomyosin
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myosin in its low energy state creates?
ATP
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myosin in its high energy state is ?
actin
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once binding sites on action are exposed, myosin heads automatically bind to actin
crossbridge formation
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letting go of actin and picking up ATP
release crossbridges
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release 1 phosphate, then back with ADP and actin
recock myosin head
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the myosin head is recocked when
it lets go of actin and picks up ATP
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only way to stop contraction?
block binding sites
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uses active transport to pump calcium back in
relaxation
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