Sometimes our body parts and our eyes twitch involuntarily. Why?
Muscle twitching is a phenomenon by itself, and it is due to aberrant conduction of nerve impulses or due to problems in the muscle working itself. A muscle reacts to a nerve impulse, because the electrolyte changes in the membrane of the muscle causes equal transport of sodium, potassium, and calcium, depending on the similar induction on the surface membrane, by a chemical called acetyl choline.
Acetyl choline is released as particles out of a nerve end, which attach themselves to the muscle membrane receptors, and cause a cascade of chemical changes inside the muscle. When calcium enters the cell it causes a reaction on the muscle protein called actin and myosin, making them combine, which shortens the muscle fibres.
This is the phenomenon of contraction of the muscle. But when individual muscle fibre ( not as a group ) have aberrations due to abnormal volleys of nerve impulses like in a disease called Motor Neuron Disease, or due to inflammatory muscle disorders like myositis, this mechanism of regularity and rhythmicity fails.
Occasionally it can happen physiologically owing to fear, emotional imbalance, stress and anxiety disorders, and also during conditions where electrolyte disturbance of the blood like dehydration etc.
Why it is common in eyes, is because of the direct observability of visibility to others, and greater perception of the muscle twitching in the eye lids. It is prominent in tongue but no body notices, unless one inspects, especially in motor neuron disease.
This condition is called fasciculation. Except in pathological diseases, it can be controlled. With adequate hydration, proper intake of electrolytes like fruit juices, salt etc, one can avoid it. Of course one should avoid stress full situation and other precipitating events.
Dr V. NAGARAAJAN
Professor Emeritus in Neuro Sciences
Tamil Nadu Govt Dr MGR Medical University
Madurai, Tamil Nadu