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Chapter 14 medical terminology
nervous system
62
Anatomy
10/17/2009

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Term
Neurons
Definition
cells that transmit impulses. commonly identified by the direction the impulse travels as afferent when the direction is toward the brain or spinal cord, or efferent, when the direction is away from the brain or spinal cord.
Term
Neuroglia
Definition
Cells that support neurons and bind them to other neurons or other tissues of the body. ALthough they do not transmit impulses, they provide a variety of activities essential to proper functioning of neurons.
Term
afferent
Definition
Carry or move inward or toward a central structure. The term afferent refers to certain arteries, veins, lymphatic vessels, and nerves.
Term
Blood-brain barrier
Definition
Protective mechanism that blocks specific substances found in the blood stream from entering delicate brain tissue.
Term
Central Nervous system
Definition
Network of nervous tissue found in the brain and spinal cord.
Term
efferent
Definition
Carry or move away from a central structure. The term efferent refers to certain arteries, veins, lymphatic vessels and nerves.
Term
nerve fiber
Definition
Projection of a neuron, especially the axon that transmits impulses
Term
neurolemma
Definition
additional sheath external to myelin that is formed by Schwann cells and found only on axons in the peripheral nervous system. Because neurilemma does not disintegrate after injury to the axon, its enclosed hollow tube provides an avenue for regeneration of injured axons.
Term
Ventricle
ventr: belly, belly side
ical: pt
Definition
Chamber or cavity of an organ that receives or holds a fluid.
Term
Cell body
Definition
enlarged structure of the neuron that contains the nucleus of the cell and various organelles. It s branching cytoplasmic projections are dendrites that carry impulses to the cell body and axons that carry impulses from the cell body. Dendrites resemble tiny branches on a tree, providing additional surface area for receiving impulses from other neurons. Axons are long, single projections ranging from a few millimeters to more than a meter in length. Axons transmit impulses to dendrites of other neurons as well as muscles and glands. Axons in the peripheral nervous system and the CNS possess a white lipoid covering called myelin sheath. This covering acts as an electrical insulator that reduces the possibility of an impulse stimulating adjacent nerves. It also acceleerates impulse transmission through the axon. ON nerves in the PNS, a myelin sheath is formed by a neuroglial cell called a Schwann cell that wraps tightly around the axon. Its exterior surface forms a thin tube called neurilemma or neurolemma. the neurilemma does not disintegrate after an axon has been crushed or severed, as does the axon and myelin sheath, but remains intact. This intact sheath provides a pathway for possible neuron regeneration after injury.
Term
oligodendrocytes
Definition
Forms the myelin sheath covering axons in the central nervous system- do not produce neurilemma, thus injury or damage to neurons located in CNS is irreparable.
Term
Nodes of Ranvier
Definition
short unmyelinated spaces between adjacent segments of myelin sheath which help speed the transmission of impulses down the axon because an impulse jumps across the nodes at a faster rate than it is able to travel through the myelinated axon.
Term
synapse
Definition
functional connection between two neurons or between a neuron and its target (muscle or gland) is in this gap or space. Impulses must travel from the axon terminal of one neuron to the dendrite of the next neuron or to its target by crossing this synapse.
Term
neuroglia
Definition
literally: nerve glue: supply nutrients and oxygen to neurons and assist in other metabolic activities. They also play an important role when the nervous system suffers injury or infection. Includes: astrocytes, Oligodendrocytes, microglia, and ependyma
Term
Astrocytes
Definition
star shaped neuroglia - provide three dimensional support for neurons and form tight sheaths around the cappilaries of the brain. These sheaths provide an obstruction called the bklood brain barrier, that keeps large molecular substances from enterinng the delicate tissue of the brain. Even so, small molecules such as water, carbon dioxide, oxygen, and alcohol readily pass from blood vessels through the barrier and enter the interstitial spaces of the brain. researchers must take the blood-brain barrier into consideration when developing drugs for treatment of brain disorders. Astrocytes also perform mildly phagocytic functions in the brain and spinal cord.
Term
Oligodendrocytes
Definition
responsible for developing myelin on neurons of the CNS.
Term
Microglia
Definition
smallest of the neuroglia possess phagocytic properties and may become very active during times of infection.
Term
Ependyma
Definition
ciliated cells that line fluid-filled cavities of the central nervous system, especially the ventricles of the brain. they assist in the circulation of cerebrospinal fluid (CSF).
Term
central nervous system
Definition
brain and spinal cord.
white matter=bundles of axons with their white lipoid myelin sheath
gray matter = unmyelinated fibers, dendrites, and nerve cell bodies
Term
Cerebrum
Definition
largest and uppermost portion of the brain. Consists of 2 hemispheres joined by the corpus callosum. Each hemisphere is divides into 5 lobs: frontal, parietal, temortal, occipital, and insula. Surface consists of numerous folds called gyri, and are separated by furrows or fissures called sulci. Cerebral cortex covers the entire cerbrum and is composed of gray matter. Major functions = sensory perception and interprtation, language, voluntary movement, memory, and the montional aspects of behavior.
Term
Cerebellum
Definition
occupies the posterior portion of the skull. All functions of the cerebellum involve movement. When the cerebrum initiates muscular movement, the cerebellum coordinates and refines it. The cerebellum also aids in maintaining equilibrium and balance.
Term
Diencephalon (interbrain)
Definition
composed of many smaller structures including the thalamus and hypothalamus.
Thalamus receives all sensory stimuli except olfactory and processes and transmits them to the appropriate centers in the cerebral cortex. In addition, the thalamus receives impulses from the cerebrum and relays them to efferent nerves.

Hypothalamus: regulates activities of the autonomic nervous system including impulses that regulate heartbeat, body temperature, and fluid balance. It also controls many endocrine functions.
Term
Thalamus
Definition
receives all sensory stimuli except olfactory and processes and transmits them to the appropriate centers in the cerebral cortex. Receives impulses from the cerebrum and relays them to efferent nerves.
Term
Hypothalamus
Definition
regulates activities of the autonomic nervous system including impulses that regulate heartbeat, body temperature, and fluid balance. It also controls many endocrine functions.
Term
Brainstem
Definition
complete the last major section of the brain. It is composed of 3 structures: the midbrain (separates the cerebrum from the brainstem), the medulla - which attaches to the spinal cord, and the pons (or bridge) connecting the midbraini to the medulla. In general, the brainstem is a pathway for impulse conduction between the brain and spinal cord. the brainstem is the origin of 10 of the 12 pairs of cranial nerves and controls respiration, blood pressure, and heart rate. Because the brainstem is the site that controls the beginning of life (the initiation of the beating heart in the fetus) and the end of life (the cessagtion of respiration and heart activity), it is sometimes called the primary brain.
Term
spinal cord
Definition
transmits sensory impulses from the body to the brain and motor impulses from the brain to muscles and organs of the body. the sensory nerve tracts are called ascending tracts because the direction of the impulse is upward. Conversely, the motor nerve tracts are called descending tracts because they carry impulses in a downward direction to muscles and organs. A cross-section of the spinal cord reveals an inner gray matter composed of cell bodies and dendrites and an outer white matter area composed of myelinated tissue of the ascending and descending tracts.
Term
Meninges
Definition
Dura mater = outermost covering of brain and spinal cord. It is tough, fibrous, and dense composed primarily of connective tissue. Beneath dura mater = subdural space which is filled with serous fluid.
Arachnoid = middle covering with spider-web appearance. Subarachnoid space contains the cerebrospinal fluid, a colorless fluid that contains proteins, glucose, urea, salts andsome white blood cells. this fluid circulates around the spinal cord and brain and through ventricles located within the inner portion of the brain. It provides nutritive substances to the CNS and adds additional protection for the brain and spinal cord by acting as a shock absorber. Normally, CSF is absorbed as rapidly as it is formed, maintaing a constant fluid voluem. Any initerference with absorption results ina collection of fluid in the brain, a condition called hydrocephalus.
Pia matter = innermost meninx. THis membrane directly adheres to the brain and spinal cord. As it passes over the brain, it follows the contours of the gyri and sulci. It contains numerous blood vessels and lymphatics that nourish the underlying tissues. because of the thiness and ddelicacy of the arachnoid and pia matter, these two meninges are collectively called the leptomeninges.
Term
PNS
Definition
Composed of all nervous tissue located outside of the spinal column and skull. IIts anatomical structures consist of 12 pairs of cranial nerves and 31 pairs of spinal nerves. Functionally, the PNS is subdivided into the somatic nervous system (SNS) and the autonomic nervous system (ANS).
Somatic nervous system consists of nerve fibers that ransmit sensory information to the brain and spinal cord, and nerve fibers that transmit impulses from the brain and spinal cord to muscles under conscious or voluntary control, such as those required for walking and talking.
The autonomic nervous system consists of nerves that control involuntary movments such as digestion, heart contraction, and vasoconstriction. It also regulates secretions by glands.
Term
Autonomic nervous system
Definition
consists of nerves that control involuntary movment, and is subdivided into sympathetic and parasympathetic divisions.
Term
sympathetic division of ANS
Definition
Dilates pupils, inhibits the flow of saliva, relaxes bronchi, accelerates heart rate, slows digestive activities, constricts visceral blood vessels.
Term
Parasympathetic Division
Definition
constricts pupils, increases the flow of saliva, constricts bronchi, slows heart rate, accelerates digestive activities, dilates visceral blood vessels.
Term
Cranial nerves
Definition
1 Olfactory
II: optic
III: oculomotos
IV: trochlear
V: Trigeminal
VI: Abducens
VII: Facial
VIII:: Vestibulocochlear
IX: Glossopharyngeal
X: Vagus
XI: Accessory
XII: Hypoglossal
Term
cerebr/o
Definition
cerebrum: Cerbrotomy - incision of the cerebrum
Term
crani/o
Definition
cranium (skull): craniomalacia
Term
dendr/o
Definition
tree
i.e. drendroid: resembling a branching tree. Dendrons: the highly branched portion of the neuron, conduct nerve impulses toward the cell body.
Term
encephal/o
Definition
brain
encephalocele. A condition in which portions of the braiin and meninges protrude through a bony midline defect in the skull. It is usually associated with a neural tube defect.
Term
gangli/o
Definition
ganglion (knotlike)
i.e. gangliectomy.
A ganglion is a mass of nerve cell bodies (gray matter) in the peripheral nervous system.
Term
gli/o
Definition
glue; neuroglial tissue
glioma: tumor composed of neuroglial tissue. A glioma is a tumor composed of neuroglial or supporting tissue of the nervous system.
Term
kinesi/o
Definition
movement
i.e. bradykinesia
Term
lept/o
Definition
thin, slender
I.e. leptomeningopathy: disease of the meninges. The leptomeninges include the pia mater and arachnoid, both of which are thin and delicate in structure, as opposed to the dura mater.
Term
lex/o
Definition
word, phrase
i.e. dyslexia: difficulty using words.
Dyslexia is difficulty or inability with reading, including the tendency to reverse letters or words when reading or writing.
Term
myel/o
Definition
bone marrow; spinal cord
poliomyelitis: inflammation of the gray matter of the spinal cord.
Term
poli/o
Definition
gray matter ( of the brain or spinal cord)
Term
narc/o
Definition
stupor, numbness, sleep
i.e. narcotic: relating to sleep. Narcotics depress the central nervous system, thus relieving pain and producing sleep
Term
neur/o
Definition
nerve
neurolysis: destruction of a nerve.
Neurolysis is sometimes performed using cryoablation or radio-frequency techniques to relieve intractable pain as a temporary or permanent measure.
Term
radicul/o
Definition
nerve root
i.e. radiculalgia: pain in the nerve root.
Term
sthen/o
Definition
strength
i.e. hypersthenia: condition of excessive strength. Hypershenia is a condition of excessive strength or tonicity of the body or a body part.
Term
Thalam/o
Definition
thalamus
i.e. thalamotomy: incision of the thalamus. Thalamotomy is performed to treat intractable pain or psychoses.
Term
thec/o
Definition
sheath (usually refers to the meninges_
intrathecal: pertaining to the space within a sheath.
Term
ton/o
Definition
tension
i.e. dystonia: usually refers to a movement disorder characterized b sustained muscle contractions resulting in a persistently abnormal posture.
Term
ventricul/o
Definition
ventricle (of heart or brain)
ventriculometry: measurement of ventricle
Term
-algesia
-algia
Definition
pain
i.e. analgesia: absence of pain
synalgia: joined pain. Synalgia is pain experienced in a part of the body other than the place of pathology. For example, right shoulder pain is commonly associated with gallstones.
Term
-asthenia
Definition
weakness, debility
I.e. myasthenia: muscle weakness
Term
-esthesia
Definition
feeling
I.e. hyperesthesia: involves a marked sensitvity to touch, pain, or other sensory stimuli.
Term
-lepsy
Definition
seizure
narcolepsy: seizure of sleep.
Term
-paresis
Definition
partial paralysis
i.e. hemiparesis: paralysis of one-half of the body; also called hemiplegia. when used alone, the term paresis means partial paralysis or motor weakness.
Term
-plegia
Definition
paralisis
ie. quadirblegia: paralysis of four extremeties.
Term
-plegia
Definition
paralisis
ie. quadirblegia: paralysis of four extremeties.
Term
-taxia
Definition
order, coordianation
i.e. ataxia: poor muscle coordination, especially when voluntary movements are attempted.
Term
pachy-
Definition
thick
pachymeningitis: inflammation of the dura mater
mening: meninges (membranes covering brain and spinal cord)
Term
para-
Definition
near, beside; beyond
paraplegia: paralysis of lower body and limbs
Term
syn-
Definition
union, together, joined
i.e. synalgia: referred pain. Pain in a deteriorated hip commonly causes reffered pain in a healthy knee.