Figure 387a,b Page 736

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Figure 38-7a,bPage 736
Muscle fibers
Biceps muscle
(contd next slide)
3
Sarcolemma
T tubule
Mitochondria
Nucleus
Sarcoplasmic reticulum
Myofibril
Z line
Myofilaments
Sarcomere
1 µm
25 µm
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Sarcomere
Z line
Actin (thin) filament
Cross bridges
Myosin (thick) filament
Sarcomere
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Figure 38-9Page 737
Neuromuscular junction
Motor nerve fiber
Cross section of spinal cord
10 µm
Neuromuscular junctions
Part of muscle fiber
Spinal nerve
Muscle
Motor nerve fiber
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Sarcolemma
T tubule
Mitochondria
Sarcoplasmic reticulum
Nucleus
Sarcomere
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Fig. 38-10(1)Page 738
1. Acetylcholine (released by a motor neuron)
combines with receptors on the muscle fiber,
causing depolarization and an action potential.
2. The impulse spreads through the T tubules,
stimulating Ca2 release from the sarcoplasmic
reticulum.
ATP binding site
Myosin filament
(contd on next slide)
Tropomyosin
Actin filament
Troponin
Active site
3. Ca2 bind to troponin, causing change in
shape. Troponin pushes tropomyosin away,
exposing active sites on actin filaments.
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4. ATP is split. The myosin head, now cocked,
binds to the exposed active site, forming a cross
bridge.
7. The actin-myosin complex binds ATP and myosin
detaches from actin.
5. Pi is released.
6. The cross bridge flexes and the actin filament
is pulled toward the center of the sarcomere.
This movement is the power stroke. ADP is
released.
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Figure 6-3Page 124
Products
Free energy decreases
Free energy (G)
Free energy (G)
Free energy increases
Products
Reactants
Course of reaction
Course of reaction
(a) Exergonic reaction (spontaneous energy
releasing
(b) Endergonic reaction (not spontaneous
energy-requiring)
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Figure 6-4Page 125
Concentration gradient
Exergonic (process occurs spontaneously)
Low entropy (S) High free energy (G)
High entropy (S) Low free energy (G)
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Figure 6-5Page 127
Adenine
Adenosine triphosphate (ATP)
Hydrolysis of ATP
H2O
Inorganic phosphate (P2)
Adenosine diphosphate (ADP)
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Figure 6-6Page 127
Exergonic reactions (release energy)
ADP
Pi
ATP
Endergonic reactions (require energy)
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