The brain is the largest and most voluminous body of the head, consisting of over 15,000 million specific nerve cells, called neurons.

Neuron, morphologically. It consists of 3 parts:
A) SOMA: The starry body of the cell.
B) Axon: It is the main extension and connecting with other neurons.
C) Dendrites: They are responsible for receiving the information from the axons of other neurons.

However, the neuron can be activated by itself?, Well no, as any engine needs its liquid element.      The neuron secretes a chemical mediators known by the name of neurotransmitters. These are what activate the neuron transmitting the messages and information from one neuron to another.

But the brain to function properly, needs not only nerve cells and the smooth functioning of neurotransmitters. Also need to be well supplied by blood, using either oxygen and glucose and has the enzymes (which are proteins) required for the biochemical reactions that will allow interneuronal transmission of information. (See Annexes 1 and 2 outline the normal brain and then the cerebral cortex in Alzheimer’s disease.)

Causes of Alzheimer’s disease, incidence and risk factors.
The cause of Alzheimer’s disease is unknown, but is not part of the normal aging process. Have been ruled out earlier theories regarding the accumulation of aluminum, lead, mercury and other substances in the body.

Biological Factors:
The neurons that control memory and thinking are impaired, interrupting the passage of messages between them. These cells develop distinct changes: senile plaques and neurofibrillary bundles (degeneration of brain tissue).

The cortex of the brain (the main source of intellectual functions) are atrophy, shrink and the spaces in the center of the brain become enlarged, thus reducing its surface.

The second significant finding is a high concentration of sticky protein called beta amyloid, which forms patches called neuritic plaques.

Inflammatory Response
Some researchers believe that beta amyloid fragments may break loose oxygen free radicals (normal chemical in the body that cause various processes are harmful when produced in excess). One of these processes may be the inflammatory response in which the immune system releases antibodies whose mission is to combat harmful agents, but, if produced in excess, can damage body cells themselves.

Genetic Factors
Researchers are closer to identifying defective genes responsible for Alzheimer’s early onset, a rare but extremely aggressive form of the disease

The brain tissue shows “neurofibrillary tangles” (twisted fragments of protein within nerve cells that clog), “neuritic plaques” (abnormal clusters of dead nerve cells and dying, other brain cells and protein) and “senile plaques” ( areas where products have accumulated around protein dead neurons). Although these changes occur to some extent in all brains with age, there are many more in the brains of people with Alzheimer’s disease.

The destruction of nerve cells (neurons) leads to a decrease in neurotransmitters (substances secreted by a neuron to send a message to another neuron), whose right balance is critical to the brain. The three neurotransmitters commonly affected by Alzheimer’s disease are acetylcholine, serotonin and norepinephrine, acetylcholine is the most affected.

By causing both structural and chemical changes in the brain, Alzheimer’s disease appears to disconnect areas of the brain that normally work together.

Approximately 4 million Americans currently suffer from Alzheimer’s disease. The most important risk factors for dementia are older age and family history of dementia. The greater the person, the greater the risk of developing this disease.

About 10% of people over 70 have significant memory problems and about half of these are caused by Alzheimer’s disease. The number of people with the disease doubles every decade after age 70 and having a close blood relative who developed AD increases your risk. Because women live longer than men, are more likely to develop it.

Two types of Alzheimer’s disease, the early onset and late onset. In the first, symptoms appear before 60 years, and in some cases, early onset disease runs in families and involves autosomal dominant, inherited mutations that may be the cause of the disease. So far, three genes have been identified early onset, which is the least common, comprising only 5 and 10% of cases.

Alzheimer’s disease late onset, which is the most common type, develops in people 60 years or more and is believed to be less likely to occur in families. Alzheimer’s disease late onset may occur in some families, but the role of genes is less direct and definitive. It is possible that these genes may not cause the problem itself, but simply increase the probability of formation of plaques and tangles or other diseases related to Alzheimer’s disease in the brain.