Question

The muscle fatigue occurs due to accumulation of
A. $CO_2$
B. Lactic acid
C. Creatine phosphate
D. Myosin ATPase

Answer 1

Hint: Muscle cells work by sensing a flow of electrical impulses from the brain that signals these muscles to contract through the release of calcium by the sarcoplasmic reticulum.

Complete answer:
Muscle fatigue occurs due to the accumulation of lactic acid. When the supply of oxygen is less and the requirement of energy is high in the body then a high amount of lactic acid is formed.

Cause of muscle fatigue:

The most important cause of skeletal muscle fatigue is considered as lactic acid accumulation.
It is also caused by the need for high energy, the variation of energy needs, and an inadequate supply of oxygen.
Fatigue can be influenced by local muscle factors, the central nervous system, and general fitness
The type of exercise also affects fatigue, high-intensity exercise may cause muscle fatigue.
Muscle fatigue can also occur depending on various factors that include reduced blood flow or small energy reserves because of improper diet, or metabolic disorders.
The shortage of substrates like adenosine triphosphate (ATP), glycogen, and creatine phosphate cause metabolic fatigue.
Accumulation of metabolites such as chloride, potassium, lactic acid, ADP, magnesium, reactive oxygen species, and inorganic phosphate can directly or indirectly lead to muscle fatigue.

Note:
- Lactic acid is a byproduct of fermentation in which cell produce energy in the absence of oxygen.
- In lactic acid fermentation, one molecule of glucose converted into two molecules of lactic acid.
- Lactic acid fermentation takes place in muscle cells.