19. Types of striated muscles, energy sources of muscle functioning, oxygen debt

Question 1

what should be mentioned in this topic?

19. Types of striated muscles, energy sources of muscle functioning, oxygen debt

Answer 1

Chemical composition of muscle tissue

Significance of macroscopic structure

Classification of muscle fibres

Dynamic Remodeling of Muscles (Training)

Muscle hypertrophy

Energy Sources of Muscle Contraction

Oxygen debt

Question 2

Chemical composition of muscle tissue

Answer 2

Muscle tissue is mainly composed of water (75%) and proteins (20%). The majority of proteins are contractile elements or passive structural proteins. Other - much less dominant - elements are albumin and different enzymes.
Energy stored in the “high energy” phosphate bonds is especially important.

Question 3

Classification of muscle fibres (skjema/bilde)

Answer 3

Question 4

Dynamic Remodeling of Muscles (Training)

Answer 4

Both of the listed factors can influence changes in the fibre spectrum.

Neural influence: If we denervate an originally red (tonic) muscle and then we innervate it with the nerves of the neighboring phasic (white) muscle, after a long regeneration period the previously red muscle becomes phasic in all features: thus usage or neural influence is important.

Genes: While, with genetic selection, it is only possible to create variations expressing rather phasic or rather tonic fiber spectra. It is proven that relative occurrence of myosin fibers may considerably vary during selection. The slow, LC-3 myosin light chain may substitute the very fast ATPase ability of LC-2.

Training results in changes in: diameter, length, strength, capillarisation and fiber composition of the muscle.

Hypertrophy: The mass of individual fibers are increased (fiber hypertrophy). An increase in number of actin and myosin filaments + increase of energy producing enzyme systems can be seen during fiber hypertrophy.

Atrophy: during long periods of inactivity muscle degradation can be seen (catabolism of myofibrilles is faster than anabolysm (synthesis)).

During the remodelling of „slow” muscles (Marathon runner, trotting horse) the mass of fibers increase slower than the nutrient- and energy storage of the myocytes.

Myoglobin content of fibers will increase

Number of mitochondria will increase

Oxydative enzyme content of mitochondria will increase

Capillarization of the muscle will increase (better oxygen and nutrient supply)

Question 5

Muscle hypertrophy

Answer 5

Muscle hypertrophy involves an increase in size of skeletal muscle through a growth in size of its component cells.

Two factors contribute to hypertrophy:

• sarcoplasmic hypertrophy, which focuses more on increased muscle glycogen storage; - myofibrillar hypertrophy, which focuses more on increased myofibril size.

Question 6

Muscle hypertrophy (picture)

Answer 6

Question 7

Energy Sources of Muscle Contraction

Answer 7

Both contraction + relaxation need ATP

Question 8

Energy sources of ADP rephosphorilation :

1. Creatin-Phosphate (CRP)
2. Anarerob Glycolysis
3. Oxidative Phosphorilation

Answer 8

1. ADP, KrP, ATP
2. The source is glucose, the end-product: (Lactic Acid, through Piruvate)

Produced energy: 4 ATP

The anaerob glycolitic process is fast. If more
ATP is used than produced, it leads to oxygen
debt. Accumulated lactic acid during anaerob
gycolysis inhibits contraction at sarcomer level.

3. Usually no ”oxygen debt” is generated. Energy source of very-long term muscle activity (characteristic to Red-muscles i.e. posture, cardiac muscle)

Pyruvate is transformed to Acetyl- Coenzyme A (not lactate).

36 ATP (and some CO2) is produced

BUT: the process is slow, the ATP resynthesis is slow, and the contraction is also slow, therefore the consumption of ATP can be equal (or less) to the energy production.

Question 9

Oxygen debt

Answer 9

Muscles covering most of their energy needs by anaerobic glycolysis during muscle work will resynthesize previously depleted energy stores in rest: in this phase resynthesis is going under aerobic conditions. Muscles show increased oxygen consumption in this phase.

If we force a muscle to work in oxygen-free environment (e.g., we stimulate the muscle through its nerve) then we can detect enhanced oxygen consumption after the work during rest. It can be explained by the muscle’s energy producing capacity under anaerobic circumstances.

Stored energy used up by anaerobic mechanisms are resynthesized during rest: muscle can replenish glycogen, creatine-phosphate, etc., by oxygen consumption.