The nervous system, parts, function, illness and diseases

1. THE NERVOUS SYSTEM
I. Description
The nervous system is the body's information gatherer, storage center and control
system. Its overall functions are to collect information about the body's external/internal states
and transfer this information to the brain (afferent system), to analyze this information, and to
send impulses out (efferent system) to initiate appropriate motor responses to meet the body's
needs. The nervous system is a collection of cells, tissues, and organs.
II. Function
The Nervous System can be split into two separate divisions: the central nervous system
and the peripheral nervous system.
The central nervous system (CNS) acts as the command center of the body. It interprets
incoming sensory information, then sends out instructions on how the body should react. The
CNS consists of two major parts: the brain and the spinal cord.
The peripheral nervous system (PNS) is the part of the nervous system outside of the
CNS. It consists mainly of nerves that extend from the brain and spinal cord to areas in the rest
of the body. Cranial nerves carry impulses to and from the brain while spinal nerves carry
impulses to and from the spinal cord. The PNS can be divided into two systems: the somatic
nervous system and the autonomic nervous system. The somatic nervous system controls the
voluntary movements of the skeletal muscles. The autonomic nervous system control activities
in the body that are involuntary or automatic. These include the actions of the heart, glands,
and digestive organs and associated parts.
The autonomic nervous system can be divided further into two subdivisions: the
parasympathetic and sympathetic nervous systems. These two subdivisions work against each
other. The parasympathetic nervous system regulates involuntary activities that keep the body
running smoothly under normal, everyday conditions. The sympathetic nervous system controls
involuntary activities that help the body respond to stressful situations.

2. III. Parts / Organ
 NERVOUS SYSTEM: set of nerves, ganglions and nervous centers that receive sensory
signal. Commands and coordinates vital functions.
 BRACHIAL PLEXUS: network of nerves of the arm.
 INTERCOSTAL NERVE: cord conducting nerve impulses between the ribs.
 RADIAL NERVE: cord conducting nerve impulses in the area of the radius.
 MEDIAN NERVE: main cord conducting nerve impulses in the upper limb.
 ULNAR NERVE: cord conducting nerve impulses in the area of the elbow.
 LUMBAR PLEXUS: network of nerves of the lower back.
 SCIATIC NERVE: cord conducting nerve impulses in the area of the thigh and lower
leg.
 COMMON PERONEAL NERVE: cord conducting nerve impulses along the inside of the
lower leg.
 SUPERFICIAL PERONEAL NERVE: cord conducting nerve impulses of the muscles
and skin of the leg.
 DIGITAL NERVE: cord conducting nerve impulses of the fingers.
 SACRAL PLEXUS: network of nerves of the sacrum.
 SPINAL CORD: substance belonging to the nervous system, found in the holes of the
vertebrae.
 CEREBELLUM: nervous centre situated under the brain.
 CEREBRUM: seat of the mental capacities.

3. IV. Illness / Disease of the Nervous System Symptoms & Cure
 ALZHEIMER DISEASE
Alzheimer disease (AD) is the most common cause of dementia in western civilization. It
affects more women than men, and the clinical course generally lasts approximately five years.
The younger the individual is at the onset of the disease, the more severe the deficits for the
patient. One famous contemporary who suffers from the disease is former U.S. President
Ronald Reagan.
Researchers continue to search for causes and cures for AD. The gene that codes for
the B-amyloid protein located on chromosome 21 is implicated in the 20% of patients for whom
there is a family history of AD. Head injury has been implicated in 3 to 5 % of AD cases. There
is a 70 to 90% decrease in the production of the enzyme that makes acetylcholine. Other
neurotransmitter abnormalities have also been implicated.
 LOCKED-IN SYNDROME
This syndrome is due to stroke, tumor or trauma to the ventral part of the rostral pons.
Lesions there render the individual quadriplegic, unable to speak and incapable of facial
movement. One would think these individuals were in a coma except that they are able to move
their eyes and if given an eye communicating device they can communicate.
 PARKINSON DISEASE
Parkinson disease (PD) is characterized by a slowing of voluntary movements,
bradykinesia, muscular rigidity and tremor at rest. These abnormalities result from a reduction
of neurons that make dopamine in the pars compacta of the substantia nigra. The axons of
these neurons normally release this neurotransmitter where they synapse, in parts of the basal
ganglia called the caudate nucleus and putamen or, collectively, the corpus striatum. Dopamine
usually works as an inhibitory neurotransmitter in the corpus striatum where it acts on
cholinergic neurons.
There are various causes for the loss of dopaminergic neurons in the substantia nigra
and the resultant signs of PD. Some evidence exists for involvement of genetic factors in the
pathogenesis of PD. For example, several large families with an autosomal, dominant
inheritance pattern of PD have now been described, and the first genetic locus for PD has been
identified in one of those families.
 HUNTINGTON DISEASE
This is an autosomally-inherited, dominant disorder in which the patient begins to
exhibit symptoms in the third to fourth decades. Patients with Huntington Disease (HD) initially
have a tendency to fidget which over months or years develops into jerky, choreiform
movements. HD usually progresses over a 10 to 25 year period. As the disease progresses it
leads to dementia and usually death from incurrent infection. There is a high incidence of
suicide among patients with HD.
Pathologically, there is atrophy of certain forebrain structures including the entire
cerebral cortex and even more notably of the caudate nucleus and putamen The head of the
caudate is reduced to a narrow brownish band of tissue that is flattened or concave. In normal
brain the ratio of small neurons to large neurons in the corpus striatum is approximately 160:1
in Huntingtons patients the ratio is reduced to 40:1 with a marked decrease in the number of
astrocytes. The gene for this disease has been isolated to the short arm of chromosome 4.

4.  CEREBELLO-OLIVARY DEGENERATION OF HOLMES
This is a rare, autosomally-inherited disease that leads to the progressive degeneration
of the cerebellar cortex and the inferior olivary nucleus within the medulla. Onset is generally in
the fourth decade. The disease results in ataxic gait, dysarthria, and tremor of the limbs.
Autopsy reveals pronounced atrophy of the cerebellum. There is almost complete loss
of Pukinje cells and an associated astrocytosis. Shrinkage is not as prominent in the olives. It
is thought that the disease begins in the cerebellum and that in the inferior olivary nucleus the
neuronal loss is secondary since the Purkinje cell is the synaptic target of the inferior olivary
nucleus neurons. There is some similarity pathologically between this disease and chronic
alcoholic degeneration in that both affect the cerebellum.
 PITUITARY ADENOMA
These tumors are benign and are usually composed of secretory cells from the anterior
lobe of the pituitary. Initially the tumor results in either an increase or decrease of hormone
production depending on whether or not the adenoma is composed of cells capable of
producing hormone. Increased levels of hormones can lead to either Cushing disease or
acromegaly.
Secondary effects of tumor growth can lead to compression of the optic chiasm which
has a position slightly above and in front of the pituitary gland. Such damage leads to visual
difficulties.
 WILSON DISEASE
(Hepatolenticular Degeneration)
This disease is caused by the inheritance of a mutation on chromosome 13. The
mutation prevents the body from eliminating excess copper. Ceruloplasmin is the protein that
binds and removes excess copper and its levels are greatly reduced in this disorder. Too much
copper in the system damages the cells of the liver and leads to cirrhosis. Neurological damage
primarily occurs in the putamen and globus pallidus, collectively known as the lenticular
nucleus.
The disease first affects the liver, and if treatment is administered early enough,
damage to the nervous system is dramatically reduced. Treatment includes the elimination of
copper containing foods such as chocolate and mushrooms. Patients are also given drugs to
chelate excess copper and eliminate it from the body.
 WERNICKE-KORSAKOFF SYNDROME
This disease, notably frequent among chronic alcoholics, is due to a deficiency of vitamin
B1 or thiamine. The poor diet of alcoholics who are suffering from this syndrome leads to
lesions and increased microhemorrhages in the mammillary bodies, thalamus and brainstem.
This syndrome can also be associated with diseases of the GI tract when there is inadequate
thiamine absorption.
Neurologic symptoms include confusion, memory loss, impaired movements and
peripheral neuropathy. Immediate administration of thiamine is usually successful in treating
the symptoms, but sometimes permanent memory loss occurs.