Brain diseases

Central Nervous System Disease
Classification and external resources
eMedicine	system/topic.htm nervous system/
MeSH	D002493
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Central nervous system diseases, also known as central nervous system disorders, are a group of neurological disorders that affect the structure or function of either the spinal cord or brain, which collectively form the central nervous system (CNS).

The spinal cord transmits sensory reception from the peripheral nervous system. It also conducts motor information to the body's skeletal muscles, cardiac muscles, smooth muscles, and glands. There are 31 pairs of spinal nerves along the spinal cord, all of which consist of both sensory and motor neurons. The spinal cord is protected by vertebrae and connects the peripheral nervous system to the brain, and it acts as a "minor" coordinating center.

The brain serves as the organic basis of cognition and exerts centralized control over the other organs of the body. The brain is protected by the skull; however, if the brain is damaged, significant impairments in cognition and physiological function or death may occur.

Addiction is a disorder of the brain's reward system which arises through transcriptional and epigenetic mechanisms and occurs over time from chronically high levels of exposure to an addictive stimulus (e.g., morphine, cocaine, sexual intercourse, gambling, etc.).

Arachnoid cysts are cerebrospinal fluid covered by arachnoidal cells that may develop on the brain or spinal cord. They are a congenital disorder, and in some cases may not show symptoms. However, if there is a large cyst, symptoms may include headache, seizures, ataxia (lack of muscle control), hemiparesis, and several others. Macrocephaly and ADHD are common among children, while presenile dementia, hydrocephalus (an abnormality of the dynamics of the cerebrospinal fluid), and urinary incontinence are symptoms for elderly patients (65 and older).

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