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| the adjustment of the lens of the eye for focusing on objects at various distances. |
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| the portion of the nervous system that controls such unconscious functions as the activities of the heart, other visceral organs, and various glands. |
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| the point on the retina of the eye where the optic nerve leaves the eyeball, at which there are no light-sensitive cells to receive visual messages. |
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| the tightly sealed walls of capillaries in the central nervous system that prevent harmful substances and pathogenic microorganisms from entering the brain or cerebrospinal fluid. |
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| the base of the brain, consisting of the midbrain, pons, and medulla oblongata. |
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| the part of the brain that lies behind the brain stem and just below the occipital lobe of the cerebrum; primary function is to coordinate skeletal muscle activity |
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| outer layer of the cerebrum |
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| the fluid that occupies the ventricles of the brain, the subarachnoid space of the meninges, and the central canal of the spinal cord; serves to protect and nourish brain and spinal tissue |
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| the portion of the brain that occupies the upper part of the cranial cavity and is responsible for thought, memory, and learned behavior |
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| a layer of connective tissue of the eye that is rich in blood vessels and provides the eye with nourishment; considered part of the uvea |
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| the front portion of the choroid of the eye that contains the ciliary muscles and adjusts the curvature of the lens for focusing |
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| the snail-shaped portion of the inner ear that contains the sensory receptors for the sense of hearing |
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Definition
| a prolonged state of unconsciousness |
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| a period of paralysis of the central nervous system accompanied by a short period of unconsciousness (usually less than five minutes and rarely more than ten minutes) caused by a blow to the head |
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Definition
| visual receptor cells located in the retina of the eye that are responsible for color vision; also called cone cells |
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Definition
| the transparent front portion of the outer layer of the eyeball |
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| a measurement of the relative intensity or loudness of sound |
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| a tough, tightly stretched membrane of skin in the ear that detects sound vibrations and transmits them by means of special bones to the cochlea |
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| a condition in which the pressure of the fluid inside the eye becomes higher than normal; can cause permanent damage to the retina if left untreated |
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Definition
| the colored portion of the uvea at the front of the eye that regulates the size of the pupil |
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Definition
| the transparent, convex structure of the eye, behind the iris, that adjusts the focus of light rays passing through it; responsible for accommodation |
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| a group of several structures located at the core of the brain that are thought to coordinate the activity of the different parts of the brain and seem to be important in generating and regulating emotions and desires |
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| the lowest part of the brain stem, located between the pons and the spinal cord, whose nerve centers control such vital functions as breathing and heartbeat |
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| triple layer of tissues that covers and protects the brain and spinal cord |
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| a biologist who specializes in the study of the nervous system |
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| a physician who specializes in disorders of the nervous system |
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| the opening in the iris through which light enters the eye |
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Definition
| a quick, automatic response to a stimulus in which the nerve impulse bypasses the brain |
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Definition
| a period of sleep characterized by small, fast brain waves similar to those of an awake person, accompanied by rapid eye movements as though watching the events off a dream |
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Definition
| the light-sensitive layer of the eye |
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Definition
| the substance in rod cells that detects light consists of a molecule derived from vitamin A suspended in a protein framework; also known as visual purple |
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| visual receptor cells located in retina of the eye that are responsible for night vision; also called rod cells |
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Definition
| glial cells that wrap around nerve-cell axons in peripheral nerves, providing them with layers of myelin sheathing that acts much like the insulation on an electrical wire |
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| the tough, white outer layer of the eye |
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| partial or complete hearing loss resulting from repeated or prolonged exposure to excessively loud sounds |
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| a serious injury of the nervous system that results when part of the brain is deprived of blood as a result of a blockage or rupture in a blood vessel |
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| the narrow junction between the axon of one nerve cell and the dendrite or cell body of another neuron |
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| chemoreceptors on the tongue responsible for the sense of taste |
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| a buzzing or ringing in the ears that occurs without any external stimulus’ often results from inner-ear damage caused by excessive exposure to loud noises |
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| the pigmented, vascular layer of the eye, consisting of the choroid, ciliary body, and iris |
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| a neck injury characterized by pain, muscle spasm, and limited motion of the neck, caused by injury to the spinal nerves that protrude from the cervical vertebrae |
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