A&P II lecture exam 1 - Anatomy and Physiology(Bio E212...

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Anatomy and Physiology (Bio E212) Lecture Exam 1 The brain weighs about 3lbs [1]. The brain is an amazing organ that acts as a control center by receiving, interpreting and directing sensory information throughout the body. The visual system is part of the central nervous system, this system gives organisms the ability to process visual detail and non-image photo responses. The human eye can be compared to a camera. The visual system interprets information from visible light and builds a representation of the surrounding environment. The lens focuses light and the cornea is responsible for bending light rays and forming images on the retina. The reflective area in the back of the eye, the image focused on the retina is inverted top to bottom and reversed right to left [2]. Vision is generated by photoreceptors in the retina, a layer of cells located at the back of the eye. Information leaves the eye from the optic nerve and crossover some nerve fibers, it occurs at the optic chiasm [1, 2,]. Each eye sees a portion of the visual field and is divided into right and left fields. Each hemisphere receives visual information from the medial half of the visual field of the eye on that side and the lateral half of the fields of the eye on the opposite side. Each eye gets information from both hemifields. The brain works on a crossed wires system, the right side of the brain control the left side and the left controls the right. The cerebral hemispheres contain a map of the entire field of vision [3]. The optic nerve is the second of the twelve pairs of cranial nerves [1]. The optic nerve is part of the central nervous system and is derived from the diencephalon. The optic nerve is located in the back of the eye [5]. The optic nerve is responsible for transferring visual
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information from the retina to other vision centers of the brain through electrical impulses, in other words the optic nerve carries images of what the eyes see to the brain [5]. The optic nerve is made up of nerve or ganglionic cells, including about a million small thread like nerve fibers that come from the retina [6]. The Optic nerve passes through optic canals of sphenoid, then converge at the ventral anterior margin of the diencephalon at the optic chiasm. At the optic chiasm fibers from the medial half of each retina cross over to the opposite side of the brain. The optic nerve is part of the eyes that gets damaged when an individual has glaucoma [7].
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