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parasympathetic nervous system
parasympathetic nervous system That part of the autonomic nervous system which generally causes bodily functions to become appropriate for calm conditions, for instance by slowing down the heart rate and promoting digestion. Nerves of the parasympathetic nervous system tend to form ganglia (ganglion...
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sympathetic nervous system
sympathetic nervous system That part of the autonomic nervous system which generally acts to stimulate the body to cope with stress, such as increasing the rate of heart beat. Nerves of the sympathetic nervous system tend to form ganglia (ganglion) beside the vertebrae, preganglionic fibres leading ...
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herpes zoster
herpes zoster infection of a ganglion (nerve center) with severe pain and a blisterlike eruption in the area of the nerve distribution, a condition called shingles. The causative organism is varicella zoster, a common, filtrable virus that is also known to cause chicken pox. Herpes zoster usually a...
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earthworm
earthworm terrestrial, cylindrical segmented worm of the class Oligochaeta. There are 2,200 earthworm species, found all over the world except in arid and arctic regions and ranging in size from 1 in. (2.5 cm) to the 11-ft (330-cm) giant worms of the tropics. Some earthworms are pallid in color, ma...
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nervous system
nervous system network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the animal kingdom have at least a rudimentary nervous system. Invertebrate animals show varying degrees of complexity in their nervous system...
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Peripheral Nervous System
Peripheral Nervous System
The peripheral nervous system (PNS) refers to all the neurons (and their supporting cells, or glia) of the body outside the brain and spinal cord (central nervous system [CNS]). The brain is the organ that decides how a person responds to what happens in the surrounding ...
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brain
brain the supervisory center of the nervous system in all vertebrates. It also serves as the site of emotions, memory, self-awareness, and thought.
Anatomy and Function
Occupying the skull cavity (cranium), the adult human brain normally weighs from 2 1/4 to 3 1/4 lb (1-1.5 kg)....
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Arthropoda
Arthropoda [Gr.,=jointed feet], largest and most diverse animal phylum. The arthropods include crustaceans , insects , centipedes , millipedes , symphylans, pauropodans, and the extinct trilobites . Arthropods are characterized by a segmented body covered by a jointed external skeleton (exoske...
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Annelida
Annelida [Lat., anellus =a ring], phylum of soft-bodied, bilaterally symmetrical (see symmetry, biological ), segmented animals, known as the segmented, or annelid, worms. Over 12,000 known species are grouped in three classes: the earthworms and freshwater worms (oligochaetes), the leeches (...
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