According to the paragrph below answer following question in your own words : In

Question

According to the paragrph below answer following question in your own words : Increasing stimulus strength causing increasing contractile responses seems to violate the “All or Nothing Principle.” How is this possible? (HINT: multiple fiber summation)

Multiple Fiber Summation. When the central nervous
system sends a weak signal to contract a muscle, the smaller
motor units of the muscle may be stimulated in preference
to the larger motor units. Then, as the strength of the signal
increases, larger and larger motor units begin to be excited as
well, with the largest motor units often having as much as 50
times the contractile force of the smallest units. This is called
the size principle. It is important because it allows the gradations
of muscle force during weak contraction to occur in
small steps, whereas the steps become progressively greater
when large amounts of force are required. The cause of this
size principle is that the smaller motor units are driven by
small motor nerve fibers, and the small motoneurons in the
spinal cord are more excitable than the larger ones, so naturally
they are excited first.
Another important feature of multiple fiber summation is
that the different motor units are driven asynchronously by
the spinal cord, so contraction alternates among motor units
one after the other, thus providing smooth contraction even
at low frequencies of nerve signals.

Explanation / Answer

In mutiple fiber summation when weak signal is produced by central nervous system the smaller motor units are excited first to contract a muscle,when strong signal generated more motor units are excited along with the larger motor units having 50 times of contactile strength of smaller ones,so more and larger motor unitsare activated the force of muscle contraction becomes strong called as size principle.Size principle allows the muscle contactions due to weak signal in small steps wheras which then become larger when more amount of force required,due to size principle Small motor neurons are naturally excited first. Different motor units of spinalcord are driven to provide smooth contraction at low frequecy of nerve signal.Muscle contraction is the activation of tension generating sites within muscle fibres ,by muscle relaxation mucle contraction stops which is the return of. the muscle fibres to th of eir normal state.[low tension ]In skeletal muscles multiple fiber summation is seen according this more the fibers [mot or units] taking part in contraction more will be the force contraction, for weak contraction smaller and few motors stimulated and in contrast to strong contaction more and more motor units are stimulated

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.