8. length tension diagram: working range and power of a muscle, heat production, muscle fatigue Flashcards
Length tension diagram: what’ is it
Length-tension curve is obtained when one stimulates muscles with maximal single impulses. The muscles are passively stretched with varying loads.
Length tension diagram: what does it show/explain
As a result of isotonic, isometric, preload or afterload experiments we can construct the range where the muscles execute normal physical work.
Length tension diagram: step 1
If we passively stretch the muscle to A, B, C distances above the resting length (L0) and in these positions we stimulate the muscle with maximal stimuli, we can obtain the isotonic maximum curve for that muscle:
Length tension diagram: step 2
If no shortening is possible, we can measure the extent of the tension and get the isometric maximum curve.
Length tension diagram: step 3
We can also conduct the experiment under preload conditions too. The result will be the preload-maximum curve.
Length tension diagram: step 4
The experiment can be conducted under afterload experiments to get the afterload-maximum curve.
Length tension diagram: summary
we can construct the area of the physiological working range of that muscle.Animals adjust their muscle length in a way that, during work, these conditions will be kept. In cardiac muscle, however, normal working range is much below the length, which would ensure maximal tension
Heat production: what is it
Muscle produces a considerable amount of heat during work. This is partly caused by ATP breakdown during contraction and partly by synthetic processes after contraction.
Heat production: 3 phases
1) resting
2) initial
3)restitution
heat production: resting
Heat is produced even when muscle is in
resting state. A considerable ratio of basal metabolic rate (BMR) comes from heat production of muscles
heat production: initial activation
Activation: The first phase of initial heat is
called activation heat, which is heat production of electromechanical coupling.
heat production: initial Contraction
: Most of the initial heat can be explained by the heat production of contraction. The role of sliding filaments and calcium pumps is important here.
heat production:Restitution:
Fast muscles generate contractile energy by utilization of their energy stores.
Aftercontraction, these stores must be filled up again: synthesis results in energy investment and heat production.
heat production: white fibre
fast
Initial heat is much larger than restitution heat. o High power for a short period is possible.
o Muscle “pays back” its oxygen debt during re-
synthesis of energy reserves.
heat production: red fibre
slow, oxidative
After short initial glycolytic phase of heat production, a long lasting oxidative period begins.
o Muscle is not exhausted and there is no oxygen debt.
