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25 Cards in this Set
- Front
- Back
accommodation |
the process of changing the shape of the lens from round and fat to thin and flat, and vice versa, so that light can be focused on the retina to accommodate vision of objects near and far away |
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acetylcholine |
one of the most common neurotransmitters of both the somatic nervous system and the parasympathetic nervous sy |
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action potential |
the change in charge that occurs when the gates of the potassium ion channels close and the gates of the sodium ion channels open; a large depolarization event that is conducted along the membrane of a nerve cell or a muscle cell |
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adaptation |
the process by which the iris adjusts the diameter of the pupil based on light conditions, thus controlling the amount of light that enters the eye and strikes the retina |
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all-or-none response |
action that occurs either completely or not at all, such as the generation of an action potential by a neuron |
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amplify |
to increase the amplitude or the extent of a vibration; see intensity |
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anterior chamber |
the space in front of the iris and behind the cornea that is filled with aqueous humour |
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aqueous humour |
a clear, watery fluid in the anterior chamber of the eye that maintains the shape of the cornea and provides oxygen and nutrients for the surrounding cells, including those of the lens and the cornea |
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astigmatism |
an uneven curvature of the cornea or lens, resulting in uneven focusing, which results in poor vision |
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auditory canal |
a short channel that funnels sound waves from outside the ear to the tympanum and amplifies sounds |
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auditory nerve |
a nerve composed of sensory fibres from the organ of Corti, the vestibular apparatus that conducts impulses to the temporal lobe of the cerebrum |
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automatic nervous system (ANS) |
a division of the peripheral nervous system that conducts nerve impulses to cardiac and smooth muscles, as well as to glands; may also be called the involuntary motor system |
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axon |
the long extension that emerges from the cell body and conducts the nerve impulse away from the cell body The axon may be up to 1 m long in motor neurons. |
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axon terminal |
numerous endings found at the end of an axon Axon terminals are enlarged into knobs that are specialized for producing, storing, and releasing neurotransmitters. |
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basilar membrane |
one of two parallel membranes that comprise the organ of Corti in the inner ear Hair cells are attached to the basilar membrane. |
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bipolar cells |
specialized sensory nerve cells located in the retina that are stimulated by either rods or cones Cones mostly have a one-to-one ratio with bipolar cells, whereas several rod cells may communicate with one bipolar cell. |
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blind spot |
the area at the back of the eyeball that is deficient in rods and cones; the area where the sensory fibres come together to form the optic nerve |
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cataract |
a cloudy or grey-white area on the lens caused by deterioration of the protein composing the lens Cataracts prevent the passing of light to the photoreceptors of the retina. |
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cell body |
the part of a neuron that contains the nucleus and other cell organelles for carrying out the metabolic reactions of the nerve cell; relays the nerve impulse from the dendrites to the axon |
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central nervous system (CNS) |
the part of the nervous system that includes the brain and spinal cord |
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chemoreceptor
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a sensory receptor that transmits information about the solute concentration in a solution or about individual kinds of molecules in solution
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cholinesterase
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an enzyme necessary to decompose acetylcholine in the synaptic cleft so that the products (choline and ethanoic acid) can be reabsorbed by the presynaptic membrane; also called acetylcholinesterase
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choroid
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the middle layer of the eye ball that lies between the sclera and retina and is highly vascular and heavily pigmented. The choroid absorbs stray light rays not detected by the photoreceptors of the retina
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ciliary muscle
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a ring of muscle behind the iris that is attached to the lens by suspensory ligaments and is involved in changing the shape of the lens
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cochlea
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contains the organ of Corti, which functions to convert the mechanical energy of sound waves into a nerve impulse
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