The central and peripheral nervous system consists of three parts. These can be named as the brain and the spinal cord. These two are often spoken of together as the central nervous system. The nerves, which proceed from the brain and spinal cord, these are forty-three in numbers that present on each side. These are named as the cerebrospinal or peripheral nerves. The third part consisting of a number of ganglia-containing nerve cells, which are profusely connected by plexuses of nerve fibres, and are situated, in the neck, thorax, and also in abdomen. This part is known as the autonomic nervous system.

The nerve cells originate or receive impulses and impressions of various sorts. They convey these to the muscles, blood vessels, and so on, by efferent nerves. These can also received by them through afferent nerves coming from the skin, organs of sense, joints, and other parts of the body. The autonomic nervous system is concerned mainly with the movement and other functions of the internal organs, secreting glands, and blood vessels, the activities of which proceed independently of the will. In a sense, the autonomic nervous system is the controller of all bodily functions.

Nervous diseases are some of the most difficult diseases in so far as their diagnosis and treatment are concerned. The brain and the spinal cord are enclosed in the skull and the spine, beyond the reach of direct examination. Since the nerves everywhere are deeply buried in the tissues. The nature of nervous diseases must be made out from the disturbances of the organs governed by the affected nerves.

Kinds of Disorders
Nervous disorders can broadly be categorized as organic and functional. In the first category some diseases are included and these diseases result in somatic or body changes. Functional disorders are those where no bodily symptoms can be recognized. Epilepsy, hysteria, and many cases of neuralgia are categorized under functional disorders, whereas, sclerosis, tumours, cysts, ruptures, or blockage in the blood vessels i.e. with consequent loss of nutrition in a part of the brain, and local inflammation constitute an organic change.

Causes and Symptoms: Many factors contribute to the production of nervous diseases. A particular temperament or a peculiar way of life can be one such factor. Some persons, particularly those of great intellectual power and artistic temperament, seem born with a nervous constitution. In this case as in the case of some somatic disorders, hereditary factors appear to play an important role. The great pressure of modern life tends to exhaust the nervous system and bring on many diseases. That is why one comes across more cases of nervous disorders among the urban population than among the villagers. The villagers are not subjected to the stresses and strains that the city folk suffer. Shock for both to the mind and the body is such as the loss of a relative, financial reverses, an unfortunate love affair, or an accident may be the starting point of chronic nervous complaints. Many poisons produced within the body during a disease and those taken in from outside, have an especially harmful action upon the nervous system. The chief among them is syphilis, which plays an important role in the production of locomotor ataxia in which there is instability of gait, general paralysis, and certain tumours of the brain and the spinal cord. In advanced life syphilis leads to degenerative changes that bring about premature loss of mental power. Chronic alcoholism may cause severe mental derangement and multiple neuritis.

Many slight afflictions of the nervous system are attributed to defects in the organs controlled by the affected nerves.

There are two main symptoms of nervous diseases. And these can be mentioned as disturbance of sensation, either in the form of loss of feeling, or of great pain, or experiencing perverted sensations such as tingling or hot flushes. Other than these the patient may experience, more or less, complete paralysis of groups of muscles. The nutritional status of all affected organs is impaired in all serious nervous diseases and injuries. As a result, localized sweating, a glassy condition of the skin, bedsores, ulcers, and even gangrene of the limbs are liable to appear in the final stages of nervous maladies. The functions of the internal organs, which are governed by the autonomic system, are not affected unless this system is diseased. The movement of the bowels and bladder are, however, governed by spinal nerves, and thus, these natural functions are impaired in all serious diseases of the spinal cord. So that difficulty of voiding or of retaining the stools and urine is experienced in such cases. When the cranial nerves are involved, definite symptoms arise. Smell, vision, hearing, touch and all other modalities of sensation are impaired or lost in cases of injury to, or disease of any of the cranial nerves. In some cases, total paralysis may result.

According to Ayurveda, most mental and nervous disorders are due to the vitiation of the three dosha namely vata, pitta, and kapha. One of the ancient texts opines that persons with a weak will power and beset with bad habits of eating and drinking fall prey to mental disorders because the three doshas are vitiated. Sushruta has advised the physician to enquire into the food and living habits of a patient suffering from nervous or mental disorders before he proceeds to diagnose the malady. Both the somatic and the mental or psychological symptoms have to be studied before a correct diagnosis can be made. This is because of the reason that in some cases the cause may be of bodily weakness. A typical case is that of syncope or fainting. A weak-willed person may not be able to withstand a mental or physical shock and may fall down with syncope.

Severe anaemia or cardiac insufficiency caused by the inability of the heart to pump the required amount of blood may also be the cause of the fainting. In some cases, the adrenal gland may be defective. It may not be producing the required amount of adrenaline to withstand the mental or physical shock as well.