Content copyright . Roger N. Braden. All rights reserved.
The first layer, the dura mater, is made of 2 layers of a white membrane. The top layer is called the periosteum, and the bottom layer, the dura. The dura lines the skull and separates the top and bottom and the right and left quadrants of the brain.
The second layer of the meninges is the arachnoid membrane. The arachnoid membrane is a thin, blood vessel filled film that covers the entire brain. There is a space between the dura and the arachnoid membrane that is called the subdural space.
The third layer is the pia mater. This layer lies against the brain and has blood vessels that reach into the depths of the brain. The pia mater covers the entire brain and follows the folds in it. There is a space between the arachnoid membrane and the pia mater called the subarachnoid space. It is in the subarachnoid space that the cerebrospinal fluid flows.
The spinal fluid is a clear, watery fluid that surrounds the brain and spinal cord that has many purposes inside the brain. First, it helps to protect the brain from trauma. Second, because the brain is floating in the spinal fluid, it puts less pressure on the bottom of the brain near the spinal cord. It also helps to pull waste from the brain and helps to transport hormones in the brain. The spinal fluid is produced and flows through 4 ventricles located inside the brain. During a traumatic injury spinal fluid can leak out of the ear or nose, or in the case of a skull fracture, can leak out through the skull. If this happens bacteria can get into the opening that the spinal fluid leaked through and can cause infections such as meningitis.
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The brain itself weighs about 3 pounds and is made up of glial cells and neurons. Glial cells are responsible for nutrition maintain chemical balance in the brain, and facilitate communications in the nervous system. Neurons are responsible for sending and receiving nerve impulses. The major part of the brain is called the cerebrum. The cerebrum is often used to refer to the brain in general (everything that lies above the cerebellum), and is the part you normally see with all the wrinkles. This part of the brain can be divided into 4 lobes: frontal, occipital, parietal, and temporal. Click here to view a diagram of the brain.
Frontal lobe is the largest lobe and is responsible for motor skills such as speech, voluntary movement, memory, intelligence and behavior. It is also responsible for guiding eye and head movement, as well as a person’s sense of orientation.
Occipital lobe is located in the back of the brain and is responsible for processing visual information. Hitting your head too hard in this region can result in damaged vision.
Parietal lobe is responsible for simultaneously processing signals from the other parts of the brain. Damage to this part of the brain can result in problems understanding language, visual problems, difficulties with recognition and orientation.
Temporal lobes, which are located on either side of the brain at ear level, are responsible for visual memory and recognition of people’s faces, as well as language memory and understanding, and the ability to interpret other people’s emotions.
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Because each part of the brain is responsible for different functions, the location of the brain damage will determine where the resulting injury will be. For example, you may see personality changes in someone who has suffered a frontal lobe injury. If you have damage to a parietal lobe, you may lose feeling on one side of your body. Since the right side of the brain affects the left side your body, and vise versa, an injury to one side of the brain will cause damage to the opposite side of the body.
Another region of the brain is the cerebellum. This fist-sized region is located at the back of the brain under the occipital lobes. The cerebellum is responsible for balance, posture, ability to control limbs, fine motor skills (such as the ability to paint or perform surgery), coordination of movements.
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The hypothalamus is another structure in the brain that sends messages to the pituitary gland, the gland that controls growth, development, hormones, various body functions and other glands. The hypothalamus controls functions such as eating, sleeping and sexual behavior. It also regulates body temperature.
When any part of the brain is damaged the results are devastating and often life changing. The damage doesn’t only affect the brain, but the body region associated with it as well.
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The Nervous System
Together, the spinal cord and the brain make up the Central Nervous System (CNS) . Most functions of the body are controlled by the CNS. The spinal cord acts as the primary information pathway between the brain and other nervous systems of the body, such as the peripheral nervous system.
Oftentimes, when a person has a traumatic brain injury there will also be spinal cord injury or injury to the CNS. Therefore, great caution has to be utilized in the initial evaluation of the injury person to identify and avoid additional injury to the spinal cord or CNS.
The American Spinal Injury Association’s Impairment Scale is as follows:
Classification / Description
A - Complete: no motor or sensory function is preserved below the level of injury, including the sacral segments S4-S5
B - Incomplete: Sensory, but not motor, function is preserved below the neurologic level and some sensation in the sacral segments S4-S5
C - Incomplete: motor function is preserved below the neurologic level, however, more than half of key muscles below the neurologic level have a muscle grade less than 3
D - Incomplete: motor function is preserved below the neurologic level, and at least half of key muscles below the neurologic level have a muscle grade of 3 or more
E - Normal: motor and sensory functions are normal
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