Twitch, Summation and Tetanus of Skeletal Muscle - Easy and Fun explanations!

the frequency of motor neuron
   
stimulation a single action potential
   
from a motor neuron will produce a
   
single contraction in muscle fibers of
   
its motor unit this isolated contraction
   
is called a twitch the tension produced
   
by a single twitch can be measured by a
   
Maia Graham which is an instrument that
   
measures the amount of tension produced
   
over time each twitch undergoes three
   
phases a latent period a contraction
   
phase and a relaxation phase during the
   
latent period the action potential is
   
being propagated along the sarcolemma
   
and calcium ions are released from the
   
sarcoplasmic reticulum
   
however contraction has not yet occurred
   
in the contraction phase calcium ions in
   
the sarcoplasm have bound to troponin
   
tropomyosin has shifted away from active
   
binding sites and crossbridges have
   
formed here the circum years are
   
actively shortening to the point of peak
   
tension in the relaxation phase tension
   
decreases as contraction stops calcium
   
ions are pumped out of the sarcoplasm
   
back into the sarcoplasmic reticulum and
   
crossbridge cycling stops this returns
   
the muscle fiber to its resting state
   
although a person can experience a
   
muscle twitch a single twitch does not
   
produce any significant muscle activity
   
in a living body a series of action
   
potentials to the muscle fibers is
   
necessary to produce a muscle
   
contraction that can produce work normal
   
muscle contraction is more sustained and
   
it can be modified by input from the
   
nervous system to produce varying
   
amounts of force this is called a graded
   
muscle response the frequency of action
   
potentials or nerve impulses from a
   
motor neuron as well as the number of
   
motor neurons transmitting action
   
potentials both affect the tension
   
produced in skeletal muscle
   
if the fibers are stimulated while a
   
previous twitch is still occurring the
   
second twitch will be stronger this
   
response is called wave summation we
   
have summation occurs because the
   
excitation contraction coupling effects
   
of successive motor neuron signaling is
   
summed or added together at the
   
molecular level summation occurs because
   
the second stimulus triggers the release
   
of more calcium ions which become
   
available to activate additional Cir
   
commuters while the muscle is still
   
contracting from the first stimuli
   
[Music]
   
summation results in greater contraction
   
of the motor unit if the frequency of
   
motor neuron signaling increases
   
summation and subsequent muscle tension
   
in the motor unit continues to rise
   
until it reaches a peak point the
   
tension at this point is about three to
   
four times greater than the tension of a
   
single twitch this state is referred to
   
as incomplete tetanus during incomplete
   
tetanus the muscle goes through quick
   
cycles of contraction with a short
   
relaxation phase for each if the
   
stimulus frequency is so high that the
   
relaxation phase disappears completely
   
the contractions become continuous in a
   
process called complete tetanus during
   
complete tetanus the concentration of
   
calcium ions in the sarcoplasm allows
   
virtually all of the sarcomeres to form
   
cross bridges and to shorten this allows
   
the contraction to continue
   
uninterrupted tetanus is the fusion of
   
contractions to produce a continuous
   
contraction

• #education
• #twitch
• #tetanus
• #complete_tetanus
• #incomplete_tetanus
• #fused_tetanus
• #unfused_tetanus
• #crossbridge
• #sliding_filament_theory
• #sarcomere
• #length_tension
• #summation
• #muscle_contraction