EXCITATION CONTRACTION
COUPLING
PAIRING OF ELECTRICAL EVENT WITH
MECHANICAL EVENT
Molecular basis
Increased sarcoplasmic calcium
concentration
Calcium binds with Trop C
This causes a conformational change
in Trop T binding to actin and also
tropomyosin
Unmasking of myosin binding sites
on actin
CROSS BRIDGE CYCLE
1)Resting state of myosin
Has ATP attached to ATP binding site
on its head
This site as it has intrinsic ATPase
activity produces ADP and Pi
, Causes rotation of myosin head
around hinge at 90 degree angle
This is energized state of myosin
head
2)EVENTS IN STIMULATE MUSCLE
Myosin-ADP-Pi complex has high
affinity for actin
Thus crossbridge is formed by
binding to actin
While binding 2 events occur : one is
power stroke when Pi gets released
from the complex. It bends the
myosin head at a 45 degree angle
and thus pull actin filament. Next is
dissociation of ADP. Thus actomysin
head remains in a rigid state.
To initiate the next cycle and to free
myosin from actin another ATP binds.
Again hydrolysis occur on myosin
head and energized state occur.
CROSS BRIDGE CYCLE
COUPLING
PAIRING OF ELECTRICAL EVENT WITH
MECHANICAL EVENT
Molecular basis
Increased sarcoplasmic calcium
concentration
Calcium binds with Trop C
This causes a conformational change
in Trop T binding to actin and also
tropomyosin
Unmasking of myosin binding sites
on actin
CROSS BRIDGE CYCLE
1)Resting state of myosin
Has ATP attached to ATP binding site
on its head
This site as it has intrinsic ATPase
activity produces ADP and Pi
, Causes rotation of myosin head
around hinge at 90 degree angle
This is energized state of myosin
head
2)EVENTS IN STIMULATE MUSCLE
Myosin-ADP-Pi complex has high
affinity for actin
Thus crossbridge is formed by
binding to actin
While binding 2 events occur : one is
power stroke when Pi gets released
from the complex. It bends the
myosin head at a 45 degree angle
and thus pull actin filament. Next is
dissociation of ADP. Thus actomysin
head remains in a rigid state.
To initiate the next cycle and to free
myosin from actin another ATP binds.
Again hydrolysis occur on myosin
head and energized state occur.
CROSS BRIDGE CYCLE
