In the center of the brain, between the cerebrum’s two hemispheres, lies the diencephalon. It consists largely of three important structures : the Thalamus, Hypothalamus, and Epithalamus. The Thalamus acts as a relay for sensory information on its way to the cerebrum and is crucial to memory and emotions. The tiny Hypothalamus exerts control over the autonomic nervous system and performs other functions, including regulating body temperature. The Epithalamus includes the pineal gland, which drew Descartes’s attentions. Instead of housing the soul, scientists now know it helps to regulate the body’s rhythms of sleeping and wakefulness.

Elements of the diencephalon link the left and right hemispheres.
Elements of the diencephalon link the left and right hemispheres.


At the back and bottom of the skull rests the cerebellum. Like the cerebrum, it too is divided into halves and deeply fissured. Its role is to coordinate movement and balance. Precise physical activities that must be practiced to be performed well-hitting a golf ball, doing gymnastics, picking a pattern of notes on the strings of a guitar-are processed in the cerebellum. The cerebellum also is known to play a role in emotion and action.

Misunderstanding of the work of neuroscientist Roger Sperry in the 1970s fed the notion that everyone is either “left brained” or “right brained.” Although each hemisphere has special functions, the two halves work closely together in a healthy mind. Humans are whole brained.


Where the brain meets the spinal cord is the brain stem. The spinal cord, the central route of nerve cells connecting brain and body, terminates in a 1.2 inch extension into the lower brain known as the medulla oblongata, home to motor and sensory nerves. Here is where the nerves from the body’s left and right sides cross each other on their way toward the cerebrum. Basic body functions such as heartbeat and respiration are controlled in the medulla.

Above the medulla lie the pons and midbrain. Pons means “bridge,” and that’s what it does-it acts as a bridge between the medulla and other brain regions. The midbrain links the pons to the diencephalon and controls reflexes of the ear and eye, such as the jolt the body experiences when startled.


Blood pumped from the heart pushes upward into the brain through two main sets of blood vessels, the internal carotid and vertebral arteries. Spiderwebs of smaller vessels, like distributary waterways at a river’s mouth, send blood into every region of the brain.

The brain uses oxygen III a hurry. While the brain weighs only about three pounds, a mere fraction of body weight, it burns 20 percent of the body’s oxygen and glucose. Most of that energy is mere upkeep, keeping the brain on the razor-sharp edge of action by maintaining the electric fields of the membranes surrounding the synaptic clefts. Actually thinking adds very little to the demand for energy-a fact that is somewhat counterintuitive for anyone who has ever struggled with a particularly difficult math problem or foreign language translation.

To get fuel to hungry brain cells, the body relies on the constant circulation of glucose. It’s a kind of sugar that circulates via the bloodstream. Neurons can’t stock-pile glucose like coins in a bank, so they require a ready supply of this source of chemical energy. Neurons use the fuel of glucose to manufacture and transport molecules of neurotransmitters and enzymes. They also use plenty of energy- half of the brain’s total, in fact-to transmit electro-chemical signals from cell to cell. The body obtains glucose from starches and sugars in the daily diet. Good sources include grain, fruits, and vegetables. During periods of intense concentration, glucose levels decline in brain regions associated with memory and learning. Such a decline can cause a feeling of fatigue in the body and the brain.

AN OLD BRAIN can be an amazingly healthy and creative one. Consider:

  • Ben Franklin left public service at age 82.
  • Mary Baker Eddy founded The Christian Science Monitor at age 86.
  • Robert Frost published his last collection of poems at age 88.
  • George Bernard Shaw was still writing plays at age 94.
  • Grandma Moses received a painting commission at age 99.

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