Normal Human Brain – photo by  John A Beal, PhDCredit: photo by John A Beal, PhD

The human brain weighs a mere three pounds; yet it is the most powerful organ of the human body.   The three main parts of the brain are the cerebrum, the cerebellum and the brain stem. 

The Cerebrum of the brain is used for remembering, problem solving, thinking and feeling and controlling movement and takes up most of the skull area.  The cerebellum, which is at the back of the head, controls coordination and balance.  The brain stem is beneath the cerebrum and in front of the cerebellum.  It connects the brain to the spinal cord and controls automatic functions such as breathing.   

Normal Brain Function 

Supplied with blood and oxygen by an elaborate vessel network that includes capillaries, veins and arteries; the brain uses about 20 percent of the oxygen and fuel carried by the blood; when thinking hard, it uses up to 50 percent. An adult brain contains about 100 billion nerve cells and branch out into what scientists call the “neuron forest.”   This forest has about a trillion connection points and it is through these that signals forming memories, thoughts and feelings travel.    

Signals move through the nerve cell as a tiny electrical charge and when it reaches a connection called a synapse, it may trigger a release of tiny bursts of chemicals called neurotransmitters.  The neurotransmitter is what carries the signal across the synapse to other cells. 

As time passes and people grow and experience life; the brain creates patterns of signal type and strength.  The patterns are a sort of “brain code” for the thoughts, memories, skills and sense of person.   The area involved in thinking, planning and remembering is the cortex. 

The Alzheimer’s Brain 

Alzheimer’s disease destroys cells mostly of the neuron type; it disrupts the way the electrical charges are carried within the cells and also the activity of the neurotransmitters; over time it dramatically shrinks the brain.  

In the advanced Alzheimer brain, the cortex shrivels up especially in the area of the hippocampus which plays a key role in the formation of new memories.  The fluid-filled spaces called ventricles grow larger.   

Tangles and Plaque in the Alzheimer’s Brain 

In the Alzheimer brain there are many less nerve cells and thus many less synapses than in a normal brain.  Between the nerve cells, scientists can see abnormal clusters of protein fragments they call plaques.  The dead and dying cells contain what the scientists call tangles.  Tangles are made up of twisted strands of another protein.  Scientists suspect that the plaques and the tangles are what cause cell death and tissue loss.  

The plaques may block the signaling between cells at the synapses.   Tangles destroy the cell transport system that is made of proteins.  In a healthy brain the transport system is like railroad tracks; a protein called tau helps the tracks stay straight.  When tangles form, the tau collapses into twisted strands.  Because the tracks can’t stay straight, they fall apart and disintegrate; essential supplies can no longer get through the cells and they die.  

Progression of Alzheimer’s in the Human Brain 

The spread of plaques and tangles through the cortex is generally in a predictable pattern.  Earliest stage of Alzheimer’s disease—may begin 20 years or more before diagnosis.  Plaques and tangles begin to form in the brain areas involved in learning and memory and thinking and planning.

Mild to moderate stage—generally lasts from 2-10 years. Plaques and tangles increase in the areas of learning and memory and thinking and planning; memory and thinking problems may interfere with social and work life.  Individuals may seem more confused and unable to form simple tasks.  Plaques and tangles spread to areas involved in speaking and understanding speech and the sense of where the boy is in relation to objects around the body.  Individuals may experience personality and behavior changes and may start to have trouble recognizing friends and family members.

Severe stage—may last from 1-5 years.  Most of the cortex is seriously damaged and the brain is shrunk dramatically.  At this stage individuals lose their abilities to communicate and to recognize friends and family members.  At this stage, they are no longer able to care for themselves.  

Currently there is no cure for Alzheimer’s disease; however, there are drugs that can slow down the progress of this disease.  As scientists and medical researchers continue to explore and learn more about the brain and the impact of Alzheimer’s; there remains the hope they will find an answer that can prevent the destruction of the brain that this disease causes.



Alzheimer’s Association 


The copyright of the article “The Alzheimer’s Brain Shows Marked Difference From Normal Brain” is owned by Cheryl Weldon and permission to republish in print or online must be granted by the author in writing.


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This is a journey of a man diagnosed with Alzheimer's disease; his account of his slow deterioration, his reactions, his emotions, his struggles.