Page 344 - Color Atlas of Biochemistry

Muscle 335

A. Neuromuscular junction

Motoneuron Action potential

End plate

Nucleus
Muscle fiber

B. Sarcoplasmatic reticulum (SR)
Transverse tubule Sarcoplasmic reticulum

Depolarization Extracellular
of membrane space
causes Ca 2
opening of A PP P A P P Cytoplasm
Ca 2 -channels P

SR
T tubule
-3
Ca 2 =10 M
SR foot Calsequestrin

-7
Ca 2 <10 M Ca 2 channel A PP P A P P P A PP P A P P P

C. Regulation by calcium ions

Troponin Ca 2 Ca 2
Myosin- exposes
binding T T Ca 2 myosin-
site on binding
actin C I site on
blocked I actin

Actin

Tropomyosin Myosin head

Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Thieme
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