The Brain Stem

The brain stem is at the base of the brain, near the spinal cord. It is only about three inches long, and consists of the medulla oblongata , the pons , and the midbrain , each about one inch long.(Kurland and Lupoff, 1999, p 57-58).

1. Medulla oblongata - in charge of many automatic functions of the brain, such as regulating blood pressure, heart rate, breathing, swallowing, and vomiting. Speech is also regulated from the medulla. It is in the medulla that the nerve fibers cross over sides, allowing the left side of the brain to control the right side of the body and vice versa. Medulla oblongata is actually Latin for "elongated marrow." Actually, the medulla is not elongated at all. As mentioned before, it's only about one inch long(Kurland and Lupoff, 1999, p. 57-58).
2. Pons - a thick white bundle of nerve fibers that has connections to various parts of the brain, mainly the cerebellum. The forebrain receives information from and sends information to the spinal cord and the peripheral nervous system through the pons.
3. Midbrain - a relay point for a variety of sensory inputs. The midbrain controls some basic responses such as the dilating or narrowing of the pupil in response to the light intensity.

Image Courtesy of Dr. Chudler of U. of Washington.

The Cerebellum

The cerebellum is in charge of posture and balance.(Kurland and Lupoff, 1999, p 58). It controls motor functions that you normally don't think about, such as walking, or lifting a cup to drink. For athletes, it is what controls their moves while playing a sport. For musicians, it is the cerebellum in charge of the fingers flying across the piano. These are procedural memories . The cerebellum is just over ten percent of the total brain size. The basal ganglia is made up for four clusters of nerve cells that relay information to and from the cerebellum.

The Limbic System

Around the top of the brain stem are a group of brain structures collectively called the limbic system . (Kurland and Lupoff, 1999, p 59).The limbic system is in charge of some of our basic emotions, such as pleasure, rage, hatred, love, and anxiety.

• amygdala
• corpus callosum
• fornix
• hippocampus
• mammillary body
• olfactory bulb
• supracallosal gyrus
• thalamus

The Cerebrum

The cerebrum , the outer layer of the brain, makes up approximately 85% of the brain's weight. ("Brain," 2000)(Kurland and Lupoff, 1999, p 59-60). The cerebral cortex is the outer surface of the cerebrum, made up of a folded grayish layer of cells("Brain," 2000). The cerebrum is split into two cerebral hemispheres by a deep fissure called the longitudinal sulcus . ("Brain," 2000) Each half is further divided into four lobes.

• Frontal lobes
  Main Function: to plan actions.
  Location: In the front of the brain before the central sulcus (a brain fissure). These are the largest of the lobes.
  
  
• Parietal lobes
  Main Function: to process information from the different senses, except for the sense of smell, which is processed in the olfactory bulbs.
  Location: Behind the frontal lobes and in front of the occipital lobes.
  
  
• Occipital lobes
  Main Function: to interpret visual information, such as size, shape, color, distance, texture, and movement.
  Location: In the back of the cerebrum. ("Brain," 2000)
  
  
• Temporal lobes
  Main Function: to process sound and memory.
  Location: The sides and lower part of the brain.
  

Many structures in the brain are known to be very important in the memory process.