Four Key Changes in the Alzheimer's Brain

Health Professional

The brain is the most complex organ in the body. It is made up of over 90 billion cells. These cells are the essence of what makes us human. The way we think, act, communicate, interact and make sense of the world is the result of how our brains work. Alzheimer's, a degenerative disease of the brain causes huge damage to the brain.

1. Brain Shrinkage

Alzheimer's disease (AD) most frequently occurs in older people and even 'normal' brains undergo changes during our lifetime. The brain weighs around 350 grams at birth and quadruples in size in the first three years of life. Then things begin to deteriorate. Brain weight starts to decline between the ages of 45 and 50 years. Brain volume decline is not the same in all areas and some regions shrink at about 1% a year while other areas remain much the same. However the brain of someone who has late stage Alzheimer's shows significant loss of mass. So a healthy brain will weigh between 1,300 and 1400 grams. The Alzheimer's brain is 10% less at between 1170 and 1260 grams, according to Oregon Health and ScienceUniversity.

2. Brain Size Decrease

Alzheimer's disease causes brain damage as the brain cells are destroyed. The cerebral cortex shrinks damaging areas involved in thinking, planning and remembering.

Shrinkage is especially severe in the hippocampus, an area of the cortex that plays a key role in formation of new memories. The ventricles (fluid-filled spaces within the brain) grow larger.

3. Microscopic Changes

Under the microscope we can see the changes that occur in the brain tissue of people with Alzheimer's disease. This is seen at autopsy with brain tissue having fewer nerve cells and synapses than a healthy brain. Plaques, abnormal clusters of protein fragments, build up between nerve cells.

Dead and dying nerve cells contain tangles, which are made up of twisted strands of another protein. It is these plaques and tangles that are believed to be the cause of Alzheimer's and they tend to spread through the cortex in a predictable pattern as Alzheimer's disease progresses.

4. Transmission Disruption

The brain performs a huge amount of complex tasks and they are coordinated and regulated by an organ no bigger than the size of a small cauliflower It controls movement, body temperature, accepts huge amounts of information and lays down different types of memory most of which we can recall at any given moment. It controls the five senses, is central to communications of all sorts, and allows us to reason, think all sorts of thoughts and feel a huge range of emotions.

In broad terms the brain acts with and is part of the central nervous system by sending messages through individual nerve cell as a tiny electrical charge.  Nerve cells connect to one another at synapses. When a charge reaches a synapse, it may trigger releases of tiny bursts of chemicals called neurotransmitters. The neurotransmitters travel across the synapse, carrying signals to other cells.

Alzheimer's disease disrupts both the way electrical charges travel within cells and the activity of neurotransmitters. So as the damage increases and more and more parts of the brain become affected so our memory, skills, behaviors and movements deteriorate.