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April 5
Chapter 7 (237-243)
7
Anatomy
Undergraduate 1
03/26/2013

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Term
Thick filaments
Definition
composed of myosin molecules
thicker
one in each layer (in the middle)
Term
Z line
Definition
formed by the joined ends of thin filaments
zig-zag line
Term
M line
Definition
the middle line
Term
thin filaments
Definition
composed of actin, troponin, and tropomyosin
thinner
2 of each in a layer
Term
actin
Definition
a small globular protein
each thin filament contains wo strands of this molecule that are twisted together
each molecule contains a binding site for a myosin head on a thick filament
Term
Myosin
Definition
thick filaments are bundles of this
each molecule is composed of a long shaft, one end of which terminates in two globular heads (like a golf club)
each myosin head has two important binding sites, one for ATP and one for thin filaments
Term
Sliding filament model
Definition
1. myosin binding sites on the actin molecules are covered in resting fibers
2. the action potential increases Ca2+ from the SR
3. Ca2+ binds troponin. Tropomyosin moves, revealing myosin binding sites
4. cross-bridge forms when myosin head binds actin
5. Power stroke= myosin head pivots moving actin. ADP and P dissociate from the myosin head
6. Myosin head releases actin when a fresh ATP binds
7. Mysoin head binds next actin. The ATP is cleaved to ADP + P; the cycle repeats
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