Central nervous system fatigue is a complex and multifaceted phenomenon that involves peripheral muscle fatigue and the failure to initiate and sustain voluntary drive to the muscles by the central nervous system. Recent studies have found that elevated levels of neurotransmitters such as serotonin, dopamine and acetylcholine play a part in CNS fatigue. Additionally, inadequate nutrition and abnormal immune responses are also believed to initiate central nervous system fatigue.
Research on central nervous fatigue has shown a direct correlation between serotonin (5-HT), dopamine and acetylcholine and the onset of CNS fatigue. Acetylcholine is released in the peripheral nervous systems to activate muscle fibers; thus, decreased levels of acetylcholine leads to noticeable muscle fatigue and a decrease in muscle strength. According to NCBI.gov, an imbalance in the level of serotonin and dopamine, specifically a spike in serotonin and a drop in dopamine, is associated with the onset of central nervous system fatigue.
Signs of Physical Exhaustion
Research on carbohydrates and branched chain amino acids have shown their direct impact on serotonin and dopamine levels in the brain. Carbohydrates are needed for the production of ATP, the body's energy source. Low blood sugar and low levels of muscle glycogen effectively lowers the rate at which ADP is converted to APT and, consequently, the build of ADP results in muscle fatigue.
Furthermore, carbohydrates and branched amino acids fight the onset of central nervous system fatigue due to their impact on amino acids such as tryptophan, which directly affect the levels of serotonin and dopamine in the brain. According to the National Forum.org, branched amino acids and trytophan have the same receptor carriers, thus when the blood level of branched amino acids is low, tryptophan freely enters the brain and stimulates the formation of serotonin, a neurotransmitter proven to initiate central nervous fatigue if rapidly increased.
- Research on carbohydrates and branched chain amino acids have shown their direct impact on serotonin and dopamine levels in the brain.
- Furthermore, carbohydrates and branched amino acids fight the onset of central nervous system fatigue due to their impact on amino acids such as tryptophan, which directly affect the levels of serotonin and dopamine in the brain.
Elevated levels of circulating cytokines, particularly TNF-alpha, IL-6, and IL-1beta are known to mediate the effect of fatigue from the muscle to the brain. Further more, abnormal immune response to viral infections are also associated with central nervous system fatigue. Antiviral enzymes Rnase L and another enzyme known a protein-kinase R are elevated in patients with central nervous system fatigue. Additionally, according to the Cleveland Clinic, B lymphocytes, T lymphocytes as well as phagocytic and complement system immune cells are believed to be a factor in central nervous system fatigue 2.
- Elevated levels of circulating cytokines, particularly TNF-alpha, IL-6, and IL-1beta are known to mediate the effect of fatigue from the muscle to the brain.
Signs of Physical Exhaustion
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- The National Forum: A Brief but Updated Scientific Look at the "F" Word: Fatigue
- Cleveland Clinic: The immune system and its role in chronic fatigue syndrome (CFS)
- Matura LA, Malone S, Jamie-Lara R, et al. A Systematic Review of Biological Mechanisms of Fatigue in Chronic Illness. Biol Res Nurs. 2018 Jul;20(4): 410–421. doi:10.1177/1099800418764326
- Rothenthal TC, Majeroni BA, Pretorius R, et al. Fatigue: An Overview. Am Fam Physician. 2008 Nov 15;78(10):1173-1179.
- Office of Women’s Health. Chronic Fatigue Syndrome. Updated April 26, 2019.
- Medline. Fatigue. Updated July 31, 2019
- Stadje R, Dorniden K, Becker A, et al. The differential diagnosis of tiredness: a systematic review. BMC Fam Pract. 2016;17:147. doi:10.1186/s12875-016-0545-5
Adam Scarano began writing as a freelancer in 2010 focusing on the fields of graphic design and media. He graduated from the Metropolitan State College of Denver with a Bachelor of Arts in English with a minor in digital media.