Unlike herbal therapy which uses external substances to supplement the body, acupuncture is concerned with stimulating and enhancing the body's self-healing power. Acupuncture is physical stimulation, which creates a cascade of positive changes inside the body to promote physiological functions, self regulation and encourage the body's self-healing abilities. In other words, acupuncture largely relies on the body's own regulatory state to accomplish its therapeutic proposes; if the health condition cannot resolve through body's own natural healing abilities, then other alternatives should be used in a timely manner. Understanding the concrete action of acupuncture gives insight to its clinical validity. 
Modern studies have revealed that acupuncture can stimulate the body's signaling systems, which speed up the healing process under certain circumstances. This means that acupuncture can either cure disease or alleviate symptoms through its multiple regulating effects. Specialists have found that the meridian system might actually correspond to a number of body tissues. Autopsy studies showed that 324 acupoints are within the range of 0.5cm to the nearest nervous pathways, in which 323 points (99.6%) are located close to the distribution of cranial or spinal nerves. In addition, certain acupoints are distributed on the same neural segment of their corresponding organs. Researchers identified 309 acupoints to look for how they are related to the distributions of the blood vessels, and the result showed that 24 points (7.77%) are located precisely on the major arteries, and 262 points (84.79%) are located next the arteries. Researchers also believed that the meridian system might correspond to the lymph system. The Conception Vessel, Governor Vessel and Girdling Vessel might be related to the lymphatic collective network; the courses of the lung meridian, stomach meridian, heart meridian, spleen meridian and bladder meridian almost match up with the superficial or deep lymph ducts that run in the relevant body regions. Physiological studies have also found that needling sensations such as tightness or heaviness might be due to muscular responses secondary to the local neural interaction. Various needling sensations might be due to specific tissues are being stimulated: nerve fiber stimulation is likely to cause numbness; blood vessel stimulation is likely to cause pain; and stimulation of the muscles, tendons and periosteums (lining on the bones) are likely to cause soreness and feelings of distension. Basically, there should be an intact neural network for the best acupuncture response.
Preclinical studies have documented the effects of acupuncture; however, they are still not able to fully explain how acupuncture works using modern scientific theory. According to the National Institute of Health, acupuncture stimulates the central nervous system (the brain and spinal cord) to release chemicals such as hormones causing biochemical changes that help regulate the body's natural healing abilities and promote physical and emotional well-being.
Specialists have concluded that acupuncture works in three major ways: as analgesia, as a regulator of the physiological system, and as an enhancer of the immune defense system. Studies in China have showed some of the following phenomena:
1.Analgesia
Acupuncture increases the threshold of pain perception; this action is mediated by stimulating the release of natural endorphins in the nervous system. According to clinical demonstrations, when the appropriate body points have been selected and the proper needling sensation is attained to stimulate the lesion, the analgesic effect can greatly be assured. For example, in angina patients, stimulating nei guan (Pc 6, on distal forearm) and when the needling sensation has traveled to the chest region, the chest pain can be relieved; in gallbladder colic, stimulating yang ling quan (Gb 34, near the knee) and when the needling sensation has traveled to the right lower chest region, the pain stops or is relieved significantly; in menstrual cramps, stimulating tai chong (Lr 3, on the feet) and when the needling sensation has traveled to the lower abdomen, the pain is usually relieved. Choosing points on the back based on the same controlling segment of the spinal nerve distribution can help to relieve pain relating to the internal organs; the results are rapid but short in duration.
2.Respiratory system
The autonomic nervous system may be closely involved in this. Acupuncture can alter respiratory movements; it can modulate the capacity of gas exchange, the oxygen exhaustion rate as well as the contraction and secretion actions of the air ways. Sample of body points to induce excitement effects are fei shu (Bl 13), da zhui (Gv 14), tai yuan (Lu 9), zu san li (St 36), ren zhong (Gv 26) and hui yin (Cv 1); while the points to induce inhibition are tian shu (St 25) and liang men (St 21).
3.Cardiovascular system
It has been found that acupuncture does little for the cardiovascular system in normal and healthy individuals; however, it has positive modulation effects in an abnormal cardiovascular system such as rapid heart rate, poor heart pumping, unstable blood pressure and poor peripheral circulation. The effects can vary according to the different physical states, point selections, and needling techniques. Acupuncture tends to slightly increase the blood pressure in normal healthy individuals; however, it is good for controlling the blood pressure in hypertensive individuals, and is especially beneficial to those with early-phase hypertension. It has poor results in late-phase hypertension or in cases accompanied by organic pathological changes.
4.Digestive system
Acupuncture works on the digestive system by regulating gastrointestinal tract movements and digestive secretions. The treatment is ideal for problems like gastritis, stomachache, stomach prolapse and ulcers. Acupuncture tends to help under-functioning intestines to resume to their normal state; for example, it helps to arrest either constipation or diarrhea. In gallstone cases, needling points like qiu xu (Gb 40), yang ling quan (Gb 34) and ri yue (Gb 24) can significantly increase the secretion of bile and thus facilitates the elimination of gallstones.
5.Urinary system
Acupuncture modulates the excretion functions of the kidneys, and also modifies the bladder emptying. These might be because it induces different neural reflex actions to enhance their functional states. However, the effects also rely on the stimulation techniques and physiological state of the body. For example, points like guan yuan (Cv 4), qu gu (Cv 2), zhong ji (Cv 3), san yin jiao (Sp 6), shen shu (Bl 23), pang guang shu (Bl 28) and ci liao (Bl 32), are effective in relieving urinary incontinence and enuresis.
6.Sex and the reproductive system
Studies have showed that when puncturing he gu (Li 4) and san yin jiao (Sp 6) in pregnant women, it can induce cervical relaxation in early pregnancy, uterine contractions at middle term and alternative mild irregular contractions and regular contractions at late term. Choosing points like he gu (Li 4), san yin jiao (Sp 6), zu san li (St 36), jiao xin (Ki 8), zhi bian (Bl 54) and qi hai (Cv 6), in various combinations, can effectively induce labor. Puncturing on shi men (Cv 5) has a contraceptive effect, and points like qi hai (Cv 6), guan yuan (Cv 4) and san yin jiao (Sp 6) can be used in fallopian tube blockage. In men, points like guan yuan (Cv 4), san yin jiao (Sp 6) and zu san li (St 36) can treat premature ejaculation; guan yuan (Cv 4), san yin jiao (Sp 6), shen shu (Bl 23), shang liao (Bl 31) and ming men (Gv 4) can treat impotence and certain types of inflammatory conditions of the sex organs. Generally, acupuncture enhances the functioning of the sex organs by modulating the axis of the hypothalamus-pituitary-sex glands.
7.Endocrine system
Acupuncture induces neural activities and affects endocrine secretions. In asthmatic individuals, stimulating points such as yu ji (Lu 10), qi hai (Cv 6), zu san li (St 36) and da zhui (Gv 14) can increase the cortisol content in the blood resulting in arresting the excessive secretion and contraction of the airways, also this elevated level can be maintained for two weeks. Sometimes, an exhausted state or adaptation phenomenon (poor response) during acupuncture treatment can also be explained by over-stimulation of the cortex in the adrenal gland. In hyperthyroidism, acupuncture helps to regulate the functional state of the thyroid gland, reduce the synthesis of T3 and T4 as well as their secretions. An example of point selection includes tian tu (Cv 22), he gu (Li 4), tai yang (Ex-Hn 5) and lian quan (Cv 23). It is said the closer of the stimulated point is to the thyroid gland, the stronger it is in effect; high frequency stimulation techniques are better than low frequency ones. In diabetic patients, puncturing on san yin jiao (Sp 6) can lower insulin secretion, while points like qu chi (Li 11) and di ji (Sp 8) can stimulate insulin secretion.
8.Nervous system
Acupuncture mediates neuro-hormonal activities, which are accomplished by neural reflexes in different levels of the body system. In epilepsy episodes, when puncturing on points like shen men (Ht 7), yin xi (Ht 6), tong li (Ht 5), bai hui (Gv 20) and da ling (Pc 7), most individuals tend to develop a regular pattern on a electroencephalogram, or lower brain waves in lesions. In studies for the activation of the cerebral cortex in healthy individuals, heavy stimulation seems to have an inhibitory effect on the motor division of the cerebral cortex while light stimulation seems to have an excitatory effect on the division. Acupuncture helps shorten recovery time in patients after lumbar spinal anesthesia. For problems of the peripheral nervous system such as facial palsy, trigeminal neuralgia, sciatica and optical nerve atrophy, acupuncture helps to reduce inflammation, arrest pain, and promote regeneration of new nerve fibers.
9.Immune system
There is plenty of evidence that acupuncture enhances immune functioning and helps to regulate various immune problems back to a normal state. Acupuncture not only increases the amount of white blood cells, but also improves their actions. Acupuncture helps cancer patients to endure surgery, e.g. puncturing points like zu san li (St 36), san yin jiao (Sp 6) and guan yuan (Cv 4) seem to improve the white cell count after three days of treatment. Acupuncture increases the number of T lymph cells, enhances its activities particularly for the effect of regulating the ratio of CD4/CD8. Chemotherapy usually leads to immune under-functioning while acupuncture treatment can markedly raise the immunoglobulin level, stimulating nei guan (Pc 6) can boost the immunoglobulin level in healthy individuals. Acupuncture also helps to reduce the level of pathological antibodies in certain diseases, for example in allergic rhinitis, after the symptoms are relieved by acupuncture treatment, the immunoglobulin G (IgG) content in the blood has decreased in most individuals.
