Muscle III (WS 17)
Tension Development in Muscle
1. Fiber length (before contraction)
2. Previous contractions
and rate of stimulation
3. Extent of fatigue (depletion of
resources)
4. Thickness of fibers
Energy Sources for Contraction
1. ATP- a primary source (allows for a few seconds of
contraction)
2. Phosphocreatine- Immediate backup, replenishes
ATP
3. Muscle Glycogen (in muscle) and blood glucose (in
blood)
4. Muscle and Blood fatty acids- reserves
ATP and Phosphocreatine
ATP: Aerobic respiration Oxygen, Glucose or fatty acids, generates up to 36 ATP's per glucose
Phosphocreatine: Anaerobic respiration, fast contraction, no O2 needed, yields only 2 ATP per glucose
Muscle Fatigue
The muscle is unable to generate power or create
tension
Sustained contraction of muscle over long time causes fatigue
Caused by a number of mechanisms
1. Central Factors: "feeling, perception" by CNS due to
lactic acid- not true. muscle exhaustion
2. Peripheral: Depletion
of ACH, ATP, and Glycogen stores
Accumulation of H+ or Pi
levels, lactate, and high ECF K+
Tetanus
Two Types:
1. Unfused Tetanus- incomplete, bumps are closer
together
Fiber partially relaxes
2. Complete/Fused Tetanus- due to a build up of calcium, is one big
bump
A lot of inhibition and troponin, because when you
contract so much, you rid of some of the elastic elements of the
muscle
No relaxation, maximum tension
Fiber Thickness
Varies depending on 1) location and 2) extent of training
the number of fibers we have is fixed early in life, and is regulated by myostatin and cytokine