Skeletal muscle contains many muscle
fibers. There have no any gap junctions between the cells. This means each
fiber behave independently. Every single muscle fiber has different threshold
which brings responses to us when different frequencies of stimulation applied
to it. Threshold is standard of a muscle contraction, then the contraction will
occur only when stimulus impulse is greater than the threshold. The muscles
fibers in muscle are not necessary to activate all of it when there is a
stimulus applied to it since different muscle has the different level of
The contraction of muscle must be
stimulated by an electrical signal called muscle action potential which changes
the electrical energy to a chemical signal and triggers the myofilament in
sliding filament mechanism.
Different type of contraction may be
created since the contraction of the muscle is occur individually. There was
few type of graded muscle response produced by different degree of contraction
in the muscle due to the different frequencies of stimulation. In this
experiment, single twitch, summation, recruitment, tetanus, muscle fatigue and
the relationship between muscle length and tension generated was determined.
is similar to nerve tissue which the fibers respond to a stimulus in an all or
none fashion which means all the muscle fibers in a motor unit will only
response to a single action potential in motor neuron. Each motor unit consists of one motor neuron which forms a
number of muscle fibers. The smaller the muscle
unit, the finer the control of the movement of the muscle.
depends on the intensity and frequency of stimulation, greater numbers of
fibers are activated. It also follows size principle. Recruitment starts when
our excitable neurons activate the smallest motor units with the smallest
fibers. The process is followed by the when some larger motor units with larger
fibers are enlisted, increasing the strength of contraction.
Summation occurs when a second stimulus arrives before
a muscle fiber has completely relaxed, and the second contraction will be
stronger than the first contraction begins when the fiber is at a higher level
of tension. The twitches will add to each other as the frequency is getting
closer together in time.
Tetanus occurs when all the twitches work together
until they form a huge contraction. The muscle of each individual will reach
the maximum tension. The tension caused by the continuous high rate of an action
potential. This will lengthen the muscle contraction and leads to muscle
fatigue when the muscle reaches the maximum of its capability and the tension
is crashed to zero.
skeletal muscle is considered fatigued when it can no longer contract. The
muscle loss its capability since the contraction of muscle fibers is limited. This
is caused by depletion of stored energy materials and the accumulation of waste
products, therefore it despite the continuation of neural stimulation.