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45 Explain muscle function in terms of, isometric tension development…
45
Explain
muscle function in terms of
Muscle tension
Tension can either be:
Passive:
tension developed in the
parallel elastic component of a muscle
Created by lengthening the muscle beyond the slack length of the tissues
When the muscle is lengthened passive component can add to the active tension
When muscle is shortened, it can become slack and not contribute to the total tension
(No energy required)
Active:
tension developed
by the contractile elements of the
muscle
(Energy required)
Initiated by the cross-bridge formation and movement of the thick & thin filament
Dependent on:
neural factors
frequency,
number and
size of motor units that are firing)
mechanical properties of the muscle fibers
isometric length-tension relationship and
force-velocity relationship
2.length-tension relationship
Direct relationship with isometric tension
development in a muscle fiber and the
length of sarcomeres in a muscle fiber.
Plateau
Optimal length at which:
maximal active tension is developed
by sarcomere
Isometric tension decreases
as muscle is lengthened
as fewer cross bridges can be
formed.
Tension decreases
as the muscle is
shortened
because of interdigitation of thin
filament (Ascending)
Total tension = Active and Passive together
Force-velocity relationship
Speed of shortening of myofilaments
The rate at which the myofilaments are able to slide
past one another and form and reform cross bridges
(changes length basically)
Force-Velocity relationship describes the relationship
between velocity of the muscle contraction
and the
force produced
For
dynamic contractions
Force Velocity relationship
should be combined with
Length tension relationship as
human movements does not occur
at a constant velocity
In
Concentric contraction
– Force and velocity
has an
inverse relationship
In
Eccentric contraction
– Force and velocity has
a direct
relationship
isometric tension
development in a muscle fiber
the length of sarcomeres
in a muscle fiber.