The brain: How it works, how it develops and some problems

Dr. BaizerNational Institute on Alcohol Abuse and Alcoholism

National Institutes of Health

Divisions of the Nervous System

Control centers of the brain

• Doctors and scientists have found that different parts of the brain are in charge of different things that you do.

• The cerebellum controls and coordinates movements of the muscles, like walking or swinging the arms. This means that the movement is smooth and controlled and you don’t fall over when you turn around.

• The outside layer of the cerebrum has special areas, which receive messages about sight, touch, hearing and taste. Other areas control movement, speech, learning, intelligence and personality.

• The brain stem is in charge of keeping the automatic systems of your body working. You don’t have to think about breathing, you just do it automatically, but you can decide if you want to hold your breath for a short time. You don’t have to think about your heart beating because your brain keeps it going automatically, even when you’re asleep.

cerebellum

Cerebrum (cortex)

Brain stem

The teenage brain

Another view…

Interesting facts about the human brain

• Do you know that your brain has around 100 billion nerve cells? It also has 1,000 billion other cells, which cover the nerve cells and the parts of the nerve cells which form the links between one cell and another and keep them healthy. These other cells are called ‘glia’ (or ‘glue’).

• Your brain keeps on developing until you are about 20 years old (or maybe even later!). By then the brain has made lots of connections which it no longer needs so it is able to get rid of any unused ones and still have billions of brain cells left to cope with whatever you may want to do.

• You can still make new connections even when you are 100 years old, so get Grandma going on the computer - she may not learn as fast as you but she can do it!

• The front of the human brain is larger than any other animal's, even the dinosaur's! The left side of your brain is usually better at problem solving, math and writing. The right side of the brain is creative and helps you to be good at art or music. The brain stores all sorts of things in the memory including facts and figures and all the smells, tastes and things you have seen, heard or touched. Your brain can also find things that you have remembered---like how to spell cerebellum.

Nerve cells are complex!

Receive info from other nerve cells

Sends info to other nerve cells

Nerve cells connect at synapses

Chemical neurotransmitter

Brain development

The brain grows at an amazing rate during development; at some points as many as 250,000 new nerve cells are being added per minute! At birth, almost all of the nerve cells that the brain will ever have are present. However, the brain continues to grow for a few years after birth, with many non-neural cells or ‘glia’ being added. In a two year old the brain is already 80% of its adult size.

Prenatal alcohol exposure inhibits brain cell production

Migration of Developing Neurons

Developing nerve cells migrate radially for long distances, ‘climbing’ along fiber-like guides or tracks made by glial cells. Migration is important for formation of cortical layers.

Migration results in cortical layers

Different kinds of nerve cells are in the different layers of the cortex. They connect to different areas of the brain and the body outside of the brain.

Prenatal alcohol exposure inhibits neuronal migration

Neurons are‘born’ here

And thenmigrate to here

control ethanol

The brain continues to develop through adolescence

MRI images of brains at ages 5-20. Colors represent cortical thickness

Many synapse connections are eliminated during adolescence

Insulation, or myelination of nerve fibers or axons also increases

Alcohol and the adolescent brain

• Because the brain is still developing in adolescence, it may be sensitive to the effects of ethanol, as we have seen for the embryonic brain. Accordingly, current research at NIAAA is using animal models to determine the long-term effects of underage binge drinking on the brain.

Brain diseases

• Diseases of the brain include Alzheimer’s disease, Parkinson's disease which are usually associated with aging.

• Strokes result from an interruption of circulation to the brain, usually because of a blood clot. This causes the damage or destruction of nearby brain tissue and a wide range of stroke symptoms; stroke is the third leading cause of death.