Mechanism of muscle contraction
Muscle is a contractile tissue helps in locomotion, maintenance of
posture.
They serve as the biological system for converting chemical energy to
mechanical energy
Muscle contraction is the shortening of myofibrils in response to
nervous stimulation.
During this the actin filaments slide over myosin filaments and link with
them forming actomyosin complexes
During muscular relaxation they delink and move away from each other
Mechanism of Muscle contraction
o Ultrastructural changes:
o It include the regular and cyclic attachment and detachment
between the myosin cross-bridges and the actin filaments .
o It is best explained by the Sliding-Filament theory proposed by
Huxley and J.Hanson
o According to this theory, muscle fibres become short and thick
during contraction by the shortening of their sarcomeres due to
sliding of myofilaments
o Actin filaments slide inward from adjacent Z-zones to the H zone
o In the H zone they completely overlap the myosin filaments and
link with them, forming actomyosin chains
o This inward movement of actin filaments brings Z zone closer
together
o So the length of I- band and that of sarcomere(region between
two adjacent Z-zones) becomes shorter.
Cross-bridge cycle
o The attachment- detachment cycle of the myosin head
o During muscular contraction, the head of the myosin filament
functions as a hook. It attaches to a binding site of F-actin, forming
a cross-bridge.
Muscle is a contractile tissue helps in locomotion, maintenance of
posture.
They serve as the biological system for converting chemical energy to
mechanical energy
Muscle contraction is the shortening of myofibrils in response to
nervous stimulation.
During this the actin filaments slide over myosin filaments and link with
them forming actomyosin complexes
During muscular relaxation they delink and move away from each other
Mechanism of Muscle contraction
o Ultrastructural changes:
o It include the regular and cyclic attachment and detachment
between the myosin cross-bridges and the actin filaments .
o It is best explained by the Sliding-Filament theory proposed by
Huxley and J.Hanson
o According to this theory, muscle fibres become short and thick
during contraction by the shortening of their sarcomeres due to
sliding of myofilaments
o Actin filaments slide inward from adjacent Z-zones to the H zone
o In the H zone they completely overlap the myosin filaments and
link with them, forming actomyosin chains
o This inward movement of actin filaments brings Z zone closer
together
o So the length of I- band and that of sarcomere(region between
two adjacent Z-zones) becomes shorter.
Cross-bridge cycle
o The attachment- detachment cycle of the myosin head
o During muscular contraction, the head of the myosin filament
functions as a hook. It attaches to a binding site of F-actin, forming
a cross-bridge.
