Transcript VII. Adjusting Muscle Tension

VII. Adjusting Muscle Tension
A. Muscles as a whole can have
graded contractions for tasks
1. A twitch contraction is a brief
contraction of all fibers in response to a
single action potential
2. Record of a contraction is a myogram
a. Has latent, contraction and
refractory sections
b. Refractory period is the time
the muscle has lost excitability
1. Short in skeletal long in
cardiac
B. Wave (temporal) summation
1. It is the increased strength of
contraction resulting from the
application of a second stimulus before
the muscle has completely relaxed after
a previous stimulus
2. A sustained contraction that permits
partial relaxation between stimuli is
called incomplete(unfused) tetanus
3. complete (fused) tetanus does not
even allow the partial relaxation
4. In treppe (staircase effect), each of
the first few contraction is stronger than
the last
C. Tension
1. A fiber has its greatest tension when
there is optimal overlap of thick and
thin filaments
2. Increasing the number of active
motor units is called recruitment
a. Prevents fatigue and stops jerky
movements
3. Active and passive tension
a. Active tension is created by
contractile elements; thick and thin
filaments
b. Passive tension is created by
elastic elements; not related to
contractions
4. Isotonic movement is a constant load
is moved through a range of motion
5. Isometric movement is no muscle
shortening but tension is increased
6. Atrophy is the wasting away because
of disuse or no nerve supply
7. Hypertrophy is increasing in fiber
diameter from forceful, repetitive
activity