muscular physiology artifact

1. Twitch Contraction & The treppe effect
M u s c u l a r p h ys i o lo g y A twitch contraction is a brief contraction of all the muscle fibers in a motor unit in response to a single
action potential in its motor neuron. A muscle contraction,
called a myogram, shows the variations of contractions. A
brief delay, called the latent period, occurs between
application of the stimulus (time zero on the graph) and the
beginning of contraction. During the latent period, the
muscle action potential sweeps over the sarcolemma and
calcium ions are released from the sarcoplasmic reticulum.
During the second phase, the contraction period (upward
tracing), repetitive power strokes are occurring, generating
tension or force of contraction. In the third phase, the Graph depicting the treppe effect
relaxation period (downward tracing), power strokes cease
because the level of Ca2+ in the sarcoplasm is decreasing to
the resting level. The concept or phenomenon of "Treppe" occurs when a muscle contracts more
forcefully after it has contracted a few times than when it first contracts. This is due to the fact that active
muscles require decreasing degrees of succeeding stimuli to elicit maximal contractions. Returning to our
example of the second set of squats feeling easier than the first, during the first set there was insufficient
warm-up, and the second set felt easier because the first set actually served as a warm-up. The
phenomenon in which the contraction strength of a muscle increases, due to increased Ca2+ availability
and enzyme efficiency during the warm-up.
Volume 1, Issue 1 01/14/13
Group A1
In this issue: Special points of interest:
Twitch contraction and the 1 ∗ Briefly highlight your point of interest here.
treppe effect
Cardiac Muscle and rigor mortis 1 ∗ Briefly highlight your point of interest here.
How skeletal muscles move 2 ∗ Briefly highlight your point of interest here.
Story Title 2 ∗ Briefly highlight your point of interest here.
Cardiac muscle and rigor mortis
Syncytium is cardiac muscle The four factors that motor neuron and all
tissue contracts as a influence the strength of fibers are innervates.
syncytium effects the muscle contractions:
autonomic nervous system. 3) Frequency of stimulation
Rigor Mortis is a noticeable 1) the number of muscle has high frequency.
sign of death, caused by fibers stimulated–
muscle fiber contraction 4) The degree of muscle
chemical changes in the strength, strength test
muscles. When someone involves a number of
cells. help you determine your
passes away the arms and legs current fitness level.
become stiff and are hard to 2) The relative size of the
move around. fibers– it is a single a

2. How skeletal muscles move
Skeletal muscle moves bones by receiving acetylcholine from a
motor nerve that triggers an action potential across the
muscle fibers. Muscle fibers contain actin and myosin, which
are the function components of muscle contraction. Movement of
a bone occurs when the muscle attached is being shortened. The
chemical reactions that cause muscle contraction generate heat
- energy conversion always generates "useless" energy; entropy
increases.
Structures unique to the skeletal muscle fibers
The structures that are unique to the skeletal The functions of a myofilament is to pull out
muscle fibers are M-Line, A-Band, I-Band, and every myofibril and the myofilaments and see
H-Zone. all of the actins and mysins.
- M-Line: Thin line all the way through 5. The sliding of a filament theory is how the
muscles produce, when you have thin and thick
- A-Band: tells the length of the myosin (also filaments that slide past one another as you
stays the same when a muscle contracts) work out and that’s what makes your muscles
eventually get stronger.
- I-Band: Distance between the myosins
- H-Zone: Distance between Actin between
same molecule. (Shrinks when muscle
contacts)
The H-Zone and I-Band are contractile because
they shorten.
The M-Line and A-Band are Excitability