The human brain is made up of 100 to 150 billion neurons. The folds of these neurons on the surface of the brain, often referred to as gray matter, allow for an increase in surface area, giving humans more space for cognitive processes. The brain is often divided into three parts: cortex, subcortex and midbrain and hindbrain.
Cortex
The cerebral cortex is the visible surface of the brain. It is usually categorized in two ways. It is broken down into two hemispheres---right and left. The cortex is also often divided into its four functional lobes---frontal, parietal, temporal and occipital.
The frontal lobe, located near the forehead, comprises one-third of the space on each hemisphere and serves several important functions. It houses the area of the brain involved in executive functions. These processes can best be understood by thinking of this region as the brain's conductor. It directs other regions of the brain to perform or go silent so complex mental processes can occur smoothly. More specifically, this area is involved in planning, decision-making, impulse control and error correction. It is also activated when performing tasks that are not well learned and overriding habitual actions, such as when you need to take a detour from a normal commuting route. The frontal lobe is also involved in articulation of speech and movement.
The parietal lobe, located at the top of the head, is involved in processing nerve impulses and in sensory integration, primarily with visual processes. The latter is commonly termed hand-eye coordination. Sensations processed in the parietal lobe include pain, temperature, touch and pressure.
Hearing is the primary function of the temporal lobe, which is located under the ears. It also functions in memory and integrating multiple sensory functions, like the partial lobe. The occipital lobe, located in the back of the head, is involved with vision, and damage to this area can result in partial or complete blindness.
Subcortex
Below the cortex lies a collection of gray matter called the subcortex. This area of the brain is generally divided into different systems. The first is the basal ganglia, which lies in each hemisphere. The basal ganglia are involved in motor control and skills learning. Disorders to this area cause either hypokinetic (poverty of moment) or hyperkinetic (excess of movement) problems. Examples include Parkinson's and Hunington's disease.
Another important part of the subcortex is the limbic system. It is primarily involved in the detection and expression of emotional responses. Specifically, the amygdala detects fearful or threatening objects, the hippocampus is involved in laughter and the connection between the amygdala, thalamus and hippocampus is associated with loving feelings. The hippocampus also plays an important role in learning, memory and detecting novelty.
Another part of the subcortex is called the diencephalon. It is composed of two structures---the thalamus and hypothalamus. The thalamus is the main sensory relay for all senses, except smell, between the sense organs. The hypothalamus lies beneath the thalamus in the center of the brain. Its functions include regulating body temperature, hunger and thirst, sexual activity and body growth.
Midbrain and Hindbrain
The midbrain and hindbrain regions, which are positioned around the brain stem, contain several important structures, such as the superior and interior colliculi. These structures are more primitive auditory and visual pathways. They provide a fast route to orient a person to stimuli before it is consciously seen or heard.
The hindbrain contains the cerebellum, which literally means "little brain." It is involved in the smooth execution of movements, because it integrates sensory feedback with motor commands. The hindbrain region also houses the medulla oblongata, which merges with the spinal cord. It regulates breathing, swallowing, heart rate and the wake-sleep cycles.
References
- "The Student's Guide to Cognitive Neuroscience"; Jamie Ward; 2006
- "The Human Brain Coloring Book"; Marian C. Diamond, Arnold B. Scheibel and Lawrence M. Elson; 1985
- How Stuff Works: "Limbic System"
