Transcript Muscle contraction types ppt

G. Homeostasis – Muscle contraction is an important
homeostatic device
1. Oxygen debt – During exercise blood vessels dilate and
blood flow increases
a. If the activity is too great and the oxygen supply is
limited then pyruvic acid cannot enter Krebs
b. Pyruvic acid is then converted to lactic acid to
access
energy – anaerobically
c. 80% of lactic acid is diffused to the liver and is
converted back to glycogen
d. 20% inefficiency results in debt
2. Fatigue – The inability of muscle to maintain the strength
of a contraction
Occurs as a lack of O2, depletion of glycogen or as a
result of lactic build up
3. Heat production – 85% of the total energy released during
contraction is used to maintain body temperature
H. Kinds of contractions – dependent on the frequency of
stimuli
·Muscle fiber contraction is “all or none”
·Within a skeletal muscle, not all fibers may be stimulated during
the same interval
·Different combinations of muscle fiber contractions may give
differing responses
·Graded responses – different degrees of skeletal muscle
shortening
1. Twitch –
a. Single, brief contraction
b. Not a normal muscle
function
2. Tetanus (summing of contractions)
a. One contraction is immediately
followed by another
b. The muscle does not completely
return to a resting state
c. The effects are added – 20-30
stimuli/sec
·Unfused (incomplete) tetanus
·Some relaxation occurs between
contractions
·The results are summed
· Fused (complete) tetanus – 80-100stimuli/sec
· No evidence of relaxation before the following contractions
· The result is a sustained muscle contraction
3. Treppe a. Skeletal muscle contracts with more force to the second
stimulus
b. Staircase phenomenon
I. Isometric & Isotonic Contractions
1. Isometric – muscle does not shorten during the
contraction
2. Isotonic – the muscle’s length changes during
contraction.
Define:
Muscle tone
Recruitment
Fast fibers (white)
Slow fibers (red)
Muscle fatigue