Spinal nerves Health Dictionary

Cranial nerves are those arising from the BRAIN.... cranial nerves

These are five pairs of CNS nerves that exit through the sacral foramen and sacral hiatus, and bring information in and out of the spinal cord. Much of their function relates to the sciatic nerve, and they bring information in from the skin sensory zones (dermatomes) of the heel, back of the legs, buttocks, and the pelvic floor.... sacral nerves

This is the lower portion of the CENTRAL NERVOUS SYSTEM which is situated within the SPINAL COLUMN. Above, it forms the direct continuation of the medulla oblongata, this part of the BRAIN changing its name to spinal cord at the foramen magnum, the large opening in the base of the skull through which it passes into the spinal canal. Below, the spinal cord extends to about the upper border of the second lumbar vertebra, where it tapers o? into a ?ne thread, known as the ?lum terminale, that is attached to the coccyx at the lower end of the spine. The spinal cord is thus considerably shorter than the spinal column, being only 37– 45 cm (15–18 inches) in length, and weighing around 30 grams.

In its course from the base of the skull to the lumbar region, the cord gives o? 31 nerves on each side, each of which arises by an anterior and a posterior root that join before the nerve emerges from the spinal canal. The openings for the nerves formed by notches on the ring of each vertebra have been mentioned under the entry for spinal column. To reach these openings, the upper nerves pass almost directly outwards, whilst lower down their obliquity increases, until below the point where the cord ends there is a sheaf of nerves, known as the cauda equina, running downwards to leave the spinal canal at their appropriate openings.

The cord is a cylinder, about the thickness of the little ?nger. It has two slightly enlarged portions, one in the lower part of the neck, the other at the last dorsal vertebra; and from these thickenings arise the nerves that pass to the upper and lower limbs. The upper four cervical nerves unite to produce the cervical plexus. From this the muscles and skin of the neck are mainly supplied, and the phrenic nerve, which runs down through the lower part of the neck and the chest to innervate the diaphragm, is given o?. The brachial plexus is formed by the union of the lower four cervical and ?rst dorsal nerves. In addition to nerves to some of the muscles in the shoulder region, and others to the skin about the shoulder and inner side of the arm, the plexus gives o? large nerves that proceed down the arm.

The thoracic or dorsal nerves, with the exception of the ?rst, do not form a plexus, but each runs around the chest along the lower margin of the rib to which it corresponds, whilst the lower six extend on to the abdomen.

The lumbar plexus is formed by the upper four lumbar nerves, and its branches are distributed to the lower part of the abdomen, and front and inner side of the thigh.

The sacral plexus is formed by parts of the fourth and ?fth lumbar nerves, and the upper three and part of the fourth sacral nerves. Much of the plexus is collected into the sciatic nerves, the largest in the body, which go to the legs.

The sympathetic system is joined by a pair of small branches given o? from each spinal nerve, close to the spine. This system consists of two parts, ?rst, a pair of cords running down on the side and front of the spine, and containing on each side three ganglia in the neck, and beneath this a ganglion opposite each vertebra. From these two ganglionated cords numerous branches are given o?, and these unite to form the second part – namely, plexuses connected with various internal organs, and provided with numerous large and irregularly placed ganglia. The chief of these plexuses are the cardiac plexus, the solar or epigastric plexus, the diaphragmatic, suprarenal, renal, spermatic, or ovarian, aortic, hypogastric and pelvic plexuses.

The spinal cord, like the brain, is surrounded by three membranes: the dura mater, arachnoid mater, and pia mater, from without inwards. The arrangement of the dura and arachnoid is much looser in the case of the cord than their application to the brain. The dura especially forms a wide tube which is separated from the cord by ?uid and from the vertebral canal by blood vessels and fat, this arrangement protecting the cord from pressure in any ordinary movements of the spine.

In section the spinal cord consists partly of grey, but mainly of white, matter. It di?ers from the upper parts of the brain in that the white matter (largely) in the cord is arranged on the surface, surrounding a mass of grey matter (largely neurons – see NEURON(E)), while in the brain the grey matter is super?cial. The arrangement of grey matter, as seen in a section across the cord, resembles the letter H. Each half of the cord possesses an anterior and a posterior horn, the masses of the two sides being joined by a wide posterior grey commissure. In the middle of this commissure lies the central canal of the cord, a small tube which is the continuation of the ventricles in the brain. The horns of grey matter reach almost to the surface of the cord, and from their ends arise the roots of the nerves that leave the cord. The white matter is divided almost completely into two halves by a posterior septum and anterior ?ssure and is further split into anterior, lateral and posterior columns.

Functions The cord is, in part, a receiver and originator of nerve impulses, and in part a conductor of such impulses along ?bres which pass through it to and from the brain. The cord contains centres able to receive sensory impressions and initiate motor instructions. These control blood-vessel diameters, eye-pupil size, sweating and breathing. The brain exerts an overall controlling in?uence and, before any incoming sensation can affect consciousness, it is usually ‘?ltered’ through the brain.

Many of these centres act autonomously. Other cells of the cord are capable of originating movements in response to impulses brought direct to them through sensory nerves, such activity being known as REFLEX ACTION. (For a fuller description of the activities of the spinal cord, see NEURON(E) – Re?ex action.)

The posterior column of the cord consists of the fasciculus gracilis and the fasciculus cuneatus, both conveying sensory impressions upwards. The lateral column contains the ventral and the dorsal spino-cerebellar tracts passing to the cerebellum, the crossed pyramidal tract of motor ?bres carrying outgoing impulses downwards together with the rubro-spinal, the spino-thalamic, the spino-tectal, and the postero-lateral tracts. And, ?nally, the anterior column contains the direct pyramidal tract of motor ?bres and an anterior mixed zone. The pyramidal tracts have the best-known course. Starting from cells near the central sulcus on the brain, the motor nerve-?bres run down through the internal capsule, pons, and medulla, in the lower part of which many of those coming from the right side of the brain cross to the left side of the spinal cord, and vice versa. Thence the ?bres run down in the crossed pyramidal tract to end beside nerve-cells in the anterior horn of the cord. From these nerve-cells other ?bres pass outwards to form the nerves that go direct to the muscles. Thus the motor nerve path from brain to muscle is divided into two sections of neurons, of which the upper exerts a controlling in?uence upon the lower, while the lower is concerned in maintaining the muscle in a state of health and good nutrition, and in directly calling it into action. (See also NERVE; NERVOUS SYSTEM.)... spinal cord

See under ANAESTHESIA.... spinal anaesthesia

Also known as the spine, this forms an important part of the skeleton, acting both as the rigid pillar which supports the upper parts of the body and as a protection to the SPINAL CORD and nerves arising from it. The spinal column is built up of a number of bones placed one upon another, which, in consequence of having a slight degree of turning-movement, are known as the vertebrae. The possession of a spinal cord supported by a vertebral column distinguishes the higher animals from the lower types, and is why they are called vertebrates. Of the vertebrates, humans alone stand absolutely erect, and this erect carriage of the body gives to the skull and vertebral column certain distinctive characters.

The human backbone is about 70 cm (28

inches) in length, and varies little in full-grown people; di?erences in height depend mainly upon the length of the lower limbs. The number of vertebrae is 33 in children, although in adult life ?ve of these fuse together to form the sacrum, and the lowest four unite in the coccyx, so that the number of separate bones is reduced to 26. Of these there are seven in the neck, known as cervical vertebrae; 12 with ribs attached, in the region of the thorax known as thoracic or dorsal vertebrae; ?ve in the loins, called lumbar vertebrae; ?ve fused to form the sacrum; and four joined in the coccyx. These numbers are expressed in a formula thus: C7, D12, L5, S5, Coc4=33.

Although the vertebrae in each of these regions have distinguishing features, all the vertebrae are constructed on the same general plan. Each has a thick, rounded, bony part in front, known as the body, and these bodies form the main thickness of the column. Behind the body of each is a ring of bone, the neural ring, these rings placed one above another forming the bony canal which lodges the spinal cord. From each side of the ring a short process of bone known as the transverse process stands out, and from the back of the ring a larger process, the spinous process, projects. These processes give attachment to the strong ligaments and muscles which unite, support, and bend the column. The spines can be seen or felt beneath the skin of the back lying in the centre of a groove between the muscular masses of the two sides, and they give to the column its name of the spinal column. One of these spines, that of the seventh cervical vertebra, is especially large and forms a distinct bony prominence, where the neck joins the back. Between the bodies of the vertebrae lies a series of thick discs of ?brocartilage known as intervertebral discs. Each disc consists of an outer portion, known as the annulus ?brosus, and an inner core, known as the nucleus pulposus. These 23 discs provide the upper part of the spine with pliability and resilience.

The ?rst and second cervical vertebrae are specially modi?ed. The ?rst vertebra, known as the atlas, is devoid of a body, but has a specially large and strong ring with two hollows upon which the skull rests, thus allowing forward and backward movements (nodding). The second vertebra, known as the axis, has a pivot on its body which ?ts into the ?rst vertebra and thus allows free rotation of the head from side to side. The spinal column has four natural curves (see diagram) which help to cushion the shocks of walking and running.

The neural rings of the vertebrae form a canal, which is wide in the neck, smaller and almost round in the dorsal region, and wide again in the lumbar vertebrae. Down the canal runs the spinal cord, and the nerves leaving the cord do so through openings between the vertebrae which are produced by notches on the upper and lower margins of each ring. The intervertebral foramina formed by these notches are so large in comparison with the nerves passing through them that there is no chance of pressure upon the latter, except in very serious injuries which dislocate and fracture the spine.... spinal column

I. Olfactory, to the nose (smell).

II. Optic, to the eye (sight).

III. Oculomotor

Trochlear, to eye-muscles.

Abducent

VI. Trigeminal, to skin of face.

VII. Facial, to muscles of face.

VIII. Vestibulocochlear, to ear (hearing and balancing).

IX. Glossopharyngeal, to tongue (taste).

X. Vagus, to heart, larynx, lungs, and stomach.

XI. Spinal accessory, to muscles in neck.

XII. Hypoglossal, to muscles of tongue.... nerves twelve nerves come off the brain:

These have several causes. Continued or repeated severe pressure may damage a nerve seriously, as in the case of a crutch pressing into the armpit and causing drop-wrist. Bruising due to a blow which drives a super?cially placed nerve against a bone may damage, say, the radial nerve behind the upper arm. A wound may sever nerves, along with other structures; this accident is specially liable to occur to the ulnar nerve in front of the wrist when a person accidentally puts a hand and arm through a pane of glass.

Symptoms When a sensory nerve is injured or diseased, sensation is immediately more or less impaired in the part supplied by the nerve. Ulceration or death of the tissue supplied by the defective nerve may occur. When the nerve in question is a motor one, the muscles governed through it are instantly paralysed. In the latter case, the portion of nerve beyond the injury degenerates and the muscles gradually waste, losing their power of contraction in response to electrical applications. Finally, deformities result and the joints become ?xed. This is particularly noticeable when the ulnar nerve is injured, the hand and ?ngers taking up a claw-like position. The skin may also be affected.

Treatment Damaged or severed (peripheral) nerve ?bres should be sewn together, using microsurgery. Careful realignment of the nerve endings gives the ?bres an excellent chance of regenerating along the right channels. Full recovery is rare but, with regular physiotherapy to keep paralysed muscles in good shape and to prevent their shortening, the patient can expect to obtain a reasonable return of function after a few weeks, with improvement continuing over several months.... nerves, injuries to

The nerves of SMELL. Each nerve detects smell by means of hair-like receptors positioned in the mucous membrane lining the roof of the nasal cavity (see NOSE).... olfactory nerves

Nerve damage can include neuropathy or neuritis, which can be caused by diabetes, nerve injury, autoimmune disease, viral infections, muscle spasms or vitamin deficiencies. Traditional medicine found a lot of treatments for nerve damage, but alternative medicine fans think that you don’t need to take a lot of pills for something that can be treated with just a cup of tea. How a Tea for Nerves Works A Tea for Nerves’ main purpose is to nourish your nervous system and induce a state of relaxation to all your nervous cells. Also, these teas can reconstruct the damaged tissue and make your body heal all affected areas. In order to be useful, a Tea for Nerves needs to contain tannins, volatile oils and minerals (manganese, magnesium, iron, preferably). Efficient Tea for Nerves When choosing a Tea for Nerves, remember that it must be both one hundred percent safe and very efficient. If you don’t know which teas to choose from, here’s a list to help you out: - Saint John’s Wort Tea – is useful for sciatica and it can bring relief to patients suffering from depression and spinal nerves damages. Take only a cup per day and avoid it at all costs if you’re on antidepressants. Also, if you’re pregnant, talk to your doctor before starting a treatment based on Saint John’s Wort Tea. - Skullcap Tea – treats a number of affections such as inflammation, arteriosclerosis, high cholesterol and epilepsy thanks to its active constituents: antioxidant flavonoids, which can repair the nervous damages and baicalin (has anti-spastic and nerve-relaxant properties). Don’t take more than 2 cups per day for a short amount of time and don’t combine it with anti-depressants and sedatives. Basil Tea – this Tea for Nerves has many medical uses and not only that it can repair the nervous ailments, but it’s also a great energy and health enhancer. You can also use it to treat asthenia, anemia, loss of appetite and digestive tract problems. Drink one or two cups per day for a short amount of time and enjoy the health benefits! Tea for Nerves Side Effects When taken properly, these teas are generally safe. However, make sure you don’t exceed the number of cups recommended per day or you’ll get diarrhea, constipation, nausea, headaches or skin rashes. If you’ve been taking one of these teas for a while and you’re experiencing some unusual reactions, talk to your doctor as soon as possible! Don’t take a Tea for Nerves if you’re pregnant, breastfeeding, on blood thinners, anticoagulants or preparing for a major surgery (these teas contains substances that may interfere with your anesthetic). The same advice for children: there are no studies to examine the treatment’s effect on them. If your doctor says it’s ok to try a Tea for Nerves, choose one that fits best your needs and enjoy its wonderful health benefits!... tea for nerves

See lumbar puncture.... spinal tap

sympathetic nerves that supply muscle fibres in the skin, around the roots of hairs. Activity of the sympathetic nervous system causes the muscles to contract, raising the hairs and giving the *gooseflesh effect of fear or cold.... pilomotor nerves

see accessory nerve.... spinal accessory nerve

Small nerve ?bres that lie upon the walls of blood vessels and connect the muscle ?bres of their middle coat with the NERVOUS SYSTEM. Through these nerves the blood vessels are retained in a state of moderate contraction. There are vasodilator nerves, through which are transmitted impulses that dilate the vessels, and, in the case of the skin vessels, produce the condition of blushing; there are also vasoconstrictor nerves which transmit impulses that constrict, or narrow, the blood vessels – as occurs on exposure to cold (see HYPOTHERMIA). Various drugs produce dilatation or contraction of the blood vessels, and several of the substances produced by ENDOCRINE GLANDS in the body have these effects: for example, ADRENALINE.... vasomotor nerves

a state of *shock accompanied by temporary paralysis of the lower extremities that results from injury to the spine and is often associated with *ileus. If the spinal cord is transected, permanent motor paralysis persists below the level of spinal-cord division.... spinal shock

the series of nerves in the sympathetic system that are distributed to the blood vessels and viscera, passing forwards and downwards from the chain of sympathetic ganglia near the spinal cord to enter the abdomen and branch profusely.... splanchnic nerves

Scoliosis A condition where the spine is curved to one side (the spine is normally straight when seen from behind). The deformity may be mobile and reversible, or ?xed; if ?xed it is accompanied by vertebral rotation and does not disappear with changes in posture. Fixed scoliosis is idiopathic (of unknown cause) in 65–80 per cent of cases. There are three main types: the infantile type occurs in boys under three and in 90 per cent of cases resolves spontaneously; the juvenile type affects 4–9 year olds and tends to be progressive. The most common type is adolescent idiopathic scoliosis; girls are affected in 90 per cent of cases and the incidence is 4 per cent. Treatment may be conservative with a ?xed brace, or surgical fusion may be needed if the curve is greater than 45 degrees. Scoliosis can occur as a congenital condition and in neuromuscular diseases where there is muscle imbalance, such as in FRIEDREICH’S ATAXIA.

Kyphosis is a backward curvature of the spine causing a hump back. It may be postural and reversible in obese people and tall adolescent girls who stoop, but it may also be ?xed. Scheuermann’s disease is the term applied to adolescent kyphosis. It is more common in girls. Senile kyphosis occurs in elderly people who probably have osteoporosis (bone weakening) and vertebral collapse.

Disc degeneration is a normal consequence of AGEING. The disc loses its resiliance and becomes unable to withstand pressure. Rupture (prolapse) of the disc may occur with physical stress. The disc between the fourth and ?fth lumbar vertebrae is most commonly involved. The jelly-like central nucleus pulposus is usually pushed out backwards, forcing the annulus ?brosus to put pressure on the nerves as they leave the spinal canal. (See PROLAPSED INTERVERTEBRAL DISC.)

Ankylosing spondylitis is an arthritic disorder of the spine in young adults, mostly men. It is a familial condition which starts with lumbar pain and sti?ness which progresses to involve the whole spine. The discs and ligaments are replaced by ?brous tissue, making the spine rigid. Treatment is physiotherapy and anti-in?ammatory drugs to try to keep the spine supple for as long as possible.

A National Association for Ankylosing Spondylitis has been formed which is open to those with the disease, their families, friends and doctors.

Spondylosis is a term which covers disc degeneration and joint degeneration in the back. OSTEOARTHRITIS is usually implicated. Pain is commonly felt in the neck and lumbar regions and in these areas the joints may become unstable. This may put pressure on the nerves leaving the spinal canal, and in the lumbar region, pain is generally felt in the distribution of the sciatic nerve – down the back of the leg. In the neck the pain may be felt down the arm. Treatment is physiotherapy; often a neck collar or lumbar support helps. Rarely surgery is needed to remove the pressure from the nerves.

Spondylolisthesis means that the spine is shifted forward. This is nearly always in the lower lumbar region and may be familial, or due to degeneration in the joints. Pressure may be put on the cauda equina. The usual complaint is of pain after exercise. Treatment is bed rest in a bad attack with surgery indicated only if there are worrying signs of cord compression.

Spinal stenosis is due to a narrowing of the spinal canal which means that the nerves become squashed together. This causes numbness with pins and needles (paraesthia) in the legs. COMPUTED TOMOGRAPHY and nuclear magnetic resonance imaging scans can show the amount of cord compression. If improving posture does not help, surgical decompression may be needed.

Whiplash injuries occur to the neck, usually as the result of a car accident when the head and neck are thrown backwards and then forwards rapidly. This causes pain and sti?ness in the neck; the arm and shoulder may feel numb. Often a support collar relieves the pain but recovery commonly takes between 18 months to three years.

Transection of the cord occurs usually as a result of trauma when the vertebral column protecting the spinal cord is fractured and becomes unstable. The cord may be concussed or it may have become sheared by the trauma and not recover (transected). Spinal concussion usually recovers after 12 hours. If the cord is transected the patient remains paralysed. (See PARALYSIS.)... spine and spinal cord, diseases and injuries of

Surgery to relieve pressure on the spinal cord or a nerve root emerging from it (see microdiscectomy). Pressure may have various causes, including a disc prolapse, a tumour or abscess of the spinal cord, or a tumour, abscess or fracture of the vertebrae. Any of these conditions can cause weakness or paralysis of the limbs and loss of bladder control.

To treat major disc prolapses and tumours, a laminectomy (removal of the bony arches of 1 or more vertebrae) to expose the affected part of the cord or nerve roots may be performed. Recovery after treatment depends on the severity and duration of the pressure, the success of the surgery in relieving the pressure, and whether any damage is sustained by the nerves during the operation.... decompression, spinal canal

(SMA) a hereditary condition in which cells of the spinal cord die and the muscles in the arms and legs become progressively weaker. Eventually the respiratory muscles are affected and death usually results from respiratory infection. Most affected individuals are wheelchair-bound by the age of 20 and few survive beyond the age of 30. The gene responsible has been located: in affected children it is inherited as a double *recessive. There are three forms of the disease, based on severity of the symptoms and the age at which they appear. Type 1 (infantile spinal muscular atrophy) is the most acute and aggressive form of the condition (see Werdnig–Hoffmann disease). Type 2 develops between the ages of 6 months and 2 years and type 3 (Kugelberg–Welander disease), the least severe form, appears between 2 and 17 years of age.... spinal muscular atrophy