in the nerve cell or its axon;
in the neuromuscular synapse;
directly in the muscle fibers.
Without understanding the basic mechanism of muscle contraction, it is impossible to accurately determine the cause of the seizures. Therefore, self-diagnosis in this case is highly undesirable.
Structure and Features of Skeletal Muscles
Skeletal muscles have a complex structure and consist of thousands of muscle fibers. Each fiber contains numerous myofibrils, within which contractile proteins—actin and myosin—are located. Under a microscope, myofibrils appear as ordered structures with a large number of muscle cell (myocyte) nuclei.
Each myocyte is equipped with a specialized contractile apparatus, oriented strictly along the cell axis. It is the coordinated work of these structures that ensures normal movement and maintains muscle tone.
The Mechanism of Muscle Fiber Contraction
The process of muscle contraction begins in the brain. A nerve impulse is transmitted along the motor nerve to the muscle fiber. With the help of the neurotransmitter acetylcholine, an electrical signal is sent to the muscle cell membrane.
The impulse then spreads into the fiber through T-shaped channels and activates specialized structures rich in calcium ions. The release of calcium triggers the convergence of actin and myosin filaments. With the help of ATP (adenosine triphosphate), a cycle of muscle contraction and relaxation occurs.
If ATP energy is insufficient or any stage of this process is disrupted, the muscle cannot relax normally. This results in persistent tension—a cramp.
Causes of Tonic Muscle Contraction
Experts identify several key causes of prolonged muscle spasms:
excessive impulses from the brain;
anemia, heart failure, influenza, altitude sickness;
hypoglycemia (low blood sugar);
deficiencies of magnesium, B vitamins, vitamin D, and L-carnitine;
hypothyroidism and diabetes;
thrombophlebitis and circulatory disorders;
excessive or irregular physical activity;
physical inactivity and a sedentary lifestyle.
Genetic and Rare Causes of Cramps
In rare cases, congenital genetic defects in contractile proteins are the cause of cramps. These pathologies include incurable hereditary diseases in which even the slightest touch can cause severe muscle spasms, especially in the lower extremities.
First Aid for Cramps
