First of all please be assured that this is a normal physiological phenomenon, and there is a professional name: physiological tremor. Physiology, as the name suggests, it is normal in the tense, tiring, fear, showing the limbs fast jitter. And in quiet, rest when this performance will disappear.
We can recall or imagine: when you first debut speech, ten thousand spectators, spotlight, silence, the judges with the same eyes staring at you ... ... or you never talked about love, and the hearts of love goddess suddenly take the initiative You watch movies, drink coffee, if at this time shaking hands, this is a normal phenomenon.
Why is it so? In general, if we want to exercise the body, we need nerve command muscle contraction. This process is very complex, first of all need to send the forehead in the forehead of the highest consciousness of the instruction, and then the front of the brain frontal lobe issued a direct signal, passed to the spinal cord anterior horn, spinal cord and then issued neurons to the muscles, the final muscle contraction. This process solves the problem that the human body can not move at will.
In addition, in the cerebellum, basal ganglia, midbrain, pons (forehead bundle), ears, spinal cord and other nerve tissue participation, but also to adjust the strength of muscle, when the muscle contraction, contraction strength; How much is the degree of diastole. This solves the problem of precise and coordinated movement.
When the instructions are delivered to the muscle, the calcium ions will flow into the axons, and then acetylcholine will be released from the nerve endings, combined with the sarcoplasmic acetylcholine receptors of the sarcolemma. Receptors and neurotransmitters, the ion channels will be open, sodium ions will flow, and then muscle cell calcium release, and troponin binding, coarse muscle filament slippery, and then muscle contraction. This process consumes a lot of adenosine triphosphate (ATP). After this series of complex processes (real world about 0.2 seconds), the muscles to achieve a strong contraction.
And if the normal human activity may have to shrink 100 times per minute, but you shrink today, 1000 times per minute. At this point, the nerve endings of the neurotransmitters, ions are unstable, more easily depolarized, so the muscle contraction is no longer stable. The result is a physiological tremor.
Of course, this is a normal tremor in the normal situation, and sickness of the quiescent tremor, idiopathic tremor, intentional tremor and flapping-like trembling, etc. are very different. In short, the former normal people can have, the latter only when the disease occurs.