Anatomy of the Brain

It is important to fully understand the anatomy of the brain when understanding traumatic brain injuries (TBIs).  Traumatic brain injuries are often very complex and in order to evaluate and assess the damage component of the TBI one must ensure they are prepared to handle the challenges of a complex medical situation with a myriad of possible prognoses.

The anatomy of the brain is complex due its intricate structure and function.  This amazing organ acts as a control center by receiving, interpreting, and directing sensory information throughout the body.  There are three major divisions of the brain.  They are:

• Forebrain – responsible for a variety of functions including receiving and processing sensory information, thinking, perceiving, producing and understanding language, and controlling motor function.
• Midbrain – and the hindbrain together make up the brainstem. The midbrain is the portion of the brainstem that connects the hindbrain and the forebrain.  This region of the brain is involved in auditory and visual responses as well as motor function.
• Hindbrain – extends from the spinal cord and is composed of the metencephalon and myelencephalon.  The metencephalon contains structures such as the pons and cerebellum.  These regions assists in maintaining balance and equillbrium, movement coordination, and the conduction of sensory information.  The myelencephanlon is composed of the medulla oblongata which is responsible for controlling such autonomic functions as breathing, heart rate, and digestion.

A healthy adult brain weighs about 2 and a half to 3 pounds, and is located inside the skull, which protects the brain from injury.

Inside the skull, the brain is covered by three think protective layers called the meninges.  The space between the meninges and the brain is filled with a clear liquid called cerebral spinal fluid.  This fluid works to keep the central nervous system healthy.

The most basic functions of the brain, such as breathing, are controlled at the deepest level, called the brain stem.  Further up in the brain, more complicated functions, such as emotions are controlled.  At the highest levels, the most complex functions such as reasoning are found.

The outermost and largest part of the brain is called the cerebrum and it controls things like thoughts and actions.  It consists of folded bulges called gyri that create deep furrows.  The cerebrum is divided into four sections, called lobes:

• Frontal Lobes – involved with decision-making, problem solving, and planning
• Occipital Lobes – involved with vision and color recognition
• Parietal Lobes – receives and processes sensory information
• Temporal Lobes – involved with emotional responses, memory, and speech

Beneath the cerebrum is the limbic system, sometimes referred to as the “emotional brain.”  The limbic system structures are:

• Amygdala – involved in emotional responses, hormonal secretions, and memory

• Cingulate Gyrus – a fold in the brain involved with sensory input concerning emotions and the regulation of aggressive behavior

• Fornix – an arching, fibrous band of nerve fibers that connect the hippocampus to the hypothalamus

• Hippocampus – sends memories out to the appropriate part of the cerebral hemisphere for long-term storage and retrievs them when necessary

• Hypothalamus – directs a multitude of important functions such as body temperature, hunger, and homeostasis

• Olfactory Cortex – receives sensory information from the olfactory bulb and is involved in the identification of odors

• Thalamus – mass of grey matter cells that relay sensory signals to and from the spinal cord and the cerebrum

Located at the back of the brain beneath the occipital lobes, is the cerebellum.  Like the cerebrum, the cerebellum is divided into two halves, called hemispheres.  The main job of the cerebellum is to control, regulate and coordinate movement, posture, and balance.