Freelance work faculty: Community Medicine

Redundancy: The brain has more cells than it needs to function normally. Redundancy may help compensate for the loss of nerve cells that occurs with aging and disease.

Formation of new connections: The brain actively compensates for the age-related decrease in nerve cells by making new connections between the remaining nerve cells.

Production of new nerve cells: Some areas of the brain may produce new nerve cells, especially after a brain injury or a stroke. These areas include the hippocampus (which is involved in the formation and retrieval of memories) and the basal ganglia (which coordinate and smooth out movements).

Thus, people who have had a brain injury or stroke can sometimes learn new skills, as occurs during occupational therapy. People can influence how quickly brain function declines. For example, physical exercise seems to slow the loss of nerve cells in areas of the brain involved in memory. Such exercise also helps keep the remaining nerve cells functioning. On the other hand, consuming two or more drinks of alcohol a day can speed the decline in brain function. As people age, blood flow to the brain may decrease by an average of 20%. The decrease in blood flow is greater in people who have atherosclerosis of the arteries to the brain (cerebrovascular disease). This disease is more likely to occur in people who have smoked for a long time or who have high blood pressure, high cholesterol, or high blood sugar (diabetes mellitus) that is not controlled by lifestyle changes or drugs. These people may lose brain cells prematurely, possibly impairing mental function. As a result, the risk of damage to blood vessels leading to vascular dementia at a relatively young age is increased.
As people age, the disks between the back bones (vertebrae) become hard and brittle, and parts of the vertebrae may overgrow. As a result, the disks lose some of their capacity to cushion, so more pressure is put on the spinal cord and on the branches of the nerves that emerge from it (spinal nerve roots). The increased pressure may injure nerve fibers at the point where they leave the spinal cord. Such injury can result in decreased sensation and sometimes decreased strength and balance. As people age, peripheral nerves may conduct impulses more slowly and release neurotransmitters is impaired, resulting in decreased sensation, slower reflexes, and often some clumsiness. Nerve conduction can slow because the myelin sheaths around nerves degenerate. Myelin sheaths are layers of tissue that insulate nerves and speed conduction of impulses.