Unlike Alzheimer's disease, which shrinks the hippocampus causing progressive memory loss, white matter disease is a more diffuse mind-robbing condition that targets small blood vessels deep within the brain's white matter. The disease hardens the tiny arteries, gradually restricting nutrients to white matter -- the connections between brain regions involved in executive abilities such as planning, organizing, problem-solving, and attention.
Parts of the Nervous System. The center of the nervous system is the brain. The brain takes in what your eyes see and ears hear, and if you decide that you want to move around, your brain tells your muscles to do it. Your brain makes your muscles move by sending tiny electrical signals to them through your nerves. Peripheral nervous system (PNS): a part of the nervous system which includes all the nerves outside of the brain and spinal cord. 2  Sympathetic nervous system: The part of your nervous system that unconsciously controls your organs and glands when you're excited or frightened.
The eye is a slightly asymmetrical globe, about an inch in diameter. Just behind the iris and pupil lies the lens, which helps to focus light on the back of the eye. Most of the eye is filled with a clear gel called the vitreous. Light projects through the pupil and the lens to the back of the eye. The inside lining of the eye is covered by special light-sensing cells that are collectively called the retina. The retina converts light into electrical impulses. Behind the eye, the optic nerve carries these impulses to the brain. The macula is a small extra-sensitive area within the retina that gives central vision. It is located in the center of the retina and contains the fovea, a small depression or pit at the center of the macula that gives the clearest vision. Eye color is created by the amount and type of pigment in the iris.