Topic: Muscles PainWhat is it ?
Most people are familiar with the sudden pain of a muscle cramp. The rapid, uncontrolled contraction, or spasm,
happens unexpectedly, with either no stimulation or some trivially small one. The muscles contraction and pain
last for several minutes, and then slowly ease. Cramps may affect any muscles, but are most common in the calves,
feet, and hands.
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Muscle Spasms and Cramps : Causes and Symptoms
Normal voluntary muscles contraction begins when electrical signals are sent from the brain through the spinal cord
along nerve cells called motor neurons. These include both the upper motor neurons within the brain and the lower
motor neurons within the spinal cord and leading out to the muscle. At the muscle, chemicals released by the motor
neuron stimulate the internal release of calcium ions from stores within the muscles cell. These calcium ions then
interact with muscle proteins within the cell, causing the proteins (actin and myosin) to slide past one another.
This motion pulls their fixed ends closer, thereby shortening the cell and, ultimately, the muscle itself.
Recapture of calcium and unlinking of actin and myosin allows the muscle fiber to relax.
Abnormal contraction may be caused by abnormal activity at any stage in this process. Certain mechanisms within
the brain and the rest of the central nervous system help regulate contraction. Interruption of these mechanisms
can cause spasm. Motor neurons that are overly sensitive may fire below their normal thresholds. The muscle
membrane itself may be over sensitive, causing contraction without stimulation. Calcium ions may not
be
recaptured quickly enough, causing prolonged contraction.
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