During the.
contraction phase, "cocked" myosin heads pivot in a "power stroke" motion.
towards the M line pulling actin inwards, thus reducing the sarcomere's.
length. A relaxation phase proceeds contraction when ADP is split into ATP.
on myosin heads (UNT, 2010). This alteration in energy allows sarcomeres to.
return to their original resting length by detaching cross bridges.
The relationship between the intensity of muscle stimulation and.
contractile force will be demonstrated by inducing a single twitch in the.
gastrocnemius frog muscle (Lab Tutor, 2010). Additional aspects of muscle.
contraction that will be investigated include: effects of stretch, wave.
summation, tetany, fatigue and contracture. By executing five stimulation.
exercises further explanation of different physiological phenomena present.
during skeletal muscle contraction is anticipated.
Materials and Methods.
I. Calibrating the Myograph.
A myograph transducer was connected to a micro-positioner on a ring stand.
The force transducer was zeroed to the baseline, and then recorded for.
approximately 5sec (Lab Tutor, 2010). A known weight between 5-50g was.
suspended from the force transducer and recorded for an additional 5sec.
correcting any residual offset present. All further output was converted to.
units of Newtons (N).
II. Equipment Setup.
The muscle stimulator was mounted to a ring stand below a force transducer.
The stimulating electrode's positive and negative BNC connectors were then.
be connected to stimulator. The muscle was suspended from the transducer by.
fishing thread with no slack or tension.
III. Frog Surgery.
The skin of the frog was cut surrounding the abdomen and pulled down and.
off the legs. By serving the hip joint the leg was removed. The.
gastrocnemius muscle was dissected away from the tibio-fibula bone, leaving.
it attached to the hip and heel. A 15cm fishing thread was attached under.
the Achilles tendon at the heel of the frog for attachment to the force.
