Figure 40.5ca
Muscle Tissue
Skeletal muscle
Nuclei
Muscle
fiber
Sarcomere
100
μ
m
Smooth muscle
Cardiac muscle
Nucleus
Muscle fibers
25
μ
m
Nucleus
Intercalated disk
50
μ
m
Figure 50.UN01
Relaxed
muscle
Contracting
muscle
Fully contracted
muscle
Sarcomere
Contracted
sarcomere
Thin
filament
Thick
filament
Figure 50.28a-5
Thin filament
Myosin head (low-
energy configuration)
ATP
Thick
filament
Myosin-
binding sites
Actin
High-energy
configuration
ATP
ADP
P
i
ADP
Cross-bridge
Low-energy
configuration
Thin filament moves
toward center of sarcomere.
P
i
3
4
2
1
5
P
i
ADP
Figure 50.26
Muscle
Bundle of
muscle fibers
Nuclei
Single muscle fiber (cell)
Plasma membrane
Myofibril
Z lines
Sarcomere
TEM
0.5
μ
m
Z line
M line
Sarcomere
Z line
Thick
filaments
(myosin)
Thin
filaments
(actin)
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Figure 50.27
Sarcomere
0.5
μ
m
Z
Z
M
Relaxed
muscle
Contracting
muscle
Fully contracted
muscle
Contracted
sarcomere
Figure 50.29
Tropomyosin
Actin
Troponin complex
Ca
2
+
-binding sites
(a) Myosin-binding sites blocked
Ca
2
+
Myosin-
binding site

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- Winter '08
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