Behind our faces and under our hair, there sits one of the most important organs in our body – our brain. This critical structure is soft and mushy (60% fat) and must be protected by a hard encasing skull. The brain not only controls our physical movements such as walking and talking, it essentially defines who we are. The tiny electric signals (action potentials) passed from neuron to neuron generate our thoughts and emotions. I find this to be the most fascinating part of human anatomy as it is associated with our identity, creativity, and what makes each of us an unique individual.
The brain is divided into the cerebrum, brainstem and cerebellum. The cerebrum is the largest part. The outer layer is made of gray matter and the inner part is made of white matter. The darker colored gray matter is made of neuron cell bodies. This layer is where most information is processed. The lighter colored white matter is made of axons that connect the neurons to send signals for communication. Axons are covered by myelin which increase the speed of conduction.
The cerebrum is divided into two hemispheres. The left hemisphere controls the right side of the body while the right hemisphere controls the left side of the body. The left hemisphere is dominant in over 90% of people since most people are right handed. In the middle of the brain, the corpus callosum allows crossing of the white matter fibers between the two hemispheres. I wonder why this interesting switch occurs. Was there an evolutional advantage?
Each hemisphere has four lobes: frontal, parietal, temporal and occipital. Each lobe has its own specialized function.
The frontal lobe is the largest and plays a part in complex functions such as our personality. It is important for decision making. The motor strip controls body movement. The Broca’s area for speech is here too. If this area is damaged, the person will have difficulty with speech and even writing.
The parietal lobe contains the somatosensory strip and controls sense of touch, temperature, and pain. It processes the different sensory information as well as spatial awareness.
The occipital lobe is at the back of the head. It is involved with vision by processing information sent from the eyes. It processes information on color, motion, and depth.
The temporal lobe is at the side of the brain and processes auditory information. It contains the Wernicke’s area which helps us understand language. The hippocampus located here is involved in memory formation. The hippocampus is a seahorse shaped structure located under the temporal lobe. It is very important in memory and learning.
We will continue with the deep brain structures in the next entry…
