6. Types of striated muscles, energy source of muscle functioning, oxygen debt Flashcards
Muscle tissue is constructed from different fibres:
fast twitch fibre,
slow twitch fibres
intermediate types as well
fast twist fibre
capable of powerful contraction and can cover energy needs by means of anaerobic glycolysis: These are „white”, or phasic muscles.
slow twist fibre
capable of more sustained work, and gaining energy only from glucose oxidation. Other names are „red”, or tonic muscle fibres.
intermediate types as well.
Fibre types are usually intermixed in most of the muscles: the relative percentage of these distinct fibre types determine the type to which a muscle belongs.
muscle type: ATPase type:
The basic difference is found in the speed of the ATPase activity
muscle type: SR pump:
The activity of the ATPase must be quickly followed by the removal of calcium: this process can also determine the speed of the calcium signal and that of the muscle twitch.
muscle type: Junction/fibra:
myoneural junction in phasic fibres provides a 1:1 fibre:nerve connection ratio. A motor nerve fibre splits in many branches 25:1 fibre:nerve ratio is normal.
muscle types: T-system:
the development of a T-tubule system can obviously increase contractile speed.
muscle type: Muscle AP/neural AP:
Red muscles do not require frequent AP discharges to contract: rare AP signals are also able to cause almost continous contraction.
muscle type: Contraction time:
The fastest phasic fibres (e.g. in ocular muscles) are able to contract totally within a few milliseconds.
muscle type: Metabolism:
By definition, it is the type of metabolism what separates muscle fibre types.
Muscle type: Fatigue:
Since red muscle is capable to produce energy continously by oxidative processes, and since lack of oxygen does not normally occur, red muscles practically are not exhaustible.
muscle type: Fibre length:
The longer the fibres are in a muscle, the more efficient becomes the mechanical movement.
energy source of muscle functioning
ATP
creation-phospahte
anaerobic glycolysis
oxidative phosphorilation
ATP
Both contraction + relaxation need ATP! ATP concentration of Myocyte :5 mmol/l
o covers the O2 need for 2-3 sec only