Page 78 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

D. Work cycle of sliding filaments (isotonic contraction)
DHPR with (heart) and with-
2+
Action out (muscle) Ca channel
potential RYR
T system
Myosin
Longitudinal
ATP Ca 2+ tubule
Tropomyosin

Actin Troponin Contraction of Striated Muscle II
Resting position
ATP- P i
2+
[Ca ] i 2+ ase
1µmol/l [Ca ] i ADP
= 1–10µmol/l
Plate 2.13
45° 90° 2+
Ca
ATP 1 Actin-myosin binding,
ATP cleavage

50° 90°
4 Loosening of actin–myosin
bond (“softening” effect
of ATP), myosin heads erect
P i

2a Myosin heads tilt
ATP due to P i release

45° 50°

3 ATP binding
With
ATP
Without ADP
ATP
Stable “rigor complex” 65
persists
(rigor mortis) 2b Final head position
after ADP release
Despopoulos, Color Atlas of Physiology © 2003 Thieme
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