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What two organ systems are decidated to maintaining homeostasis? |
nervous and endocrine systems |
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How does the endocrine system communicate? |
chemical messengers secreted into the blood |
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What are these chemical messengers more commonly known as? |
hormones |
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How does the nervous system communicate? |
electrical and chemical means to send messages very quickly from cell to cell |
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What is the study of the nervous system? |
neurobiology |
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What are the primary subdisciplines of neurobiology? |
neuroanatomy (study of structure) and neurophysiology (study of function) |
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What are the 2 major anatomical subdivisions of the nervous system? |
Central Nervous System (CNS) and Peripheral Nervous System (PNS) |
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What does the CNS consist of? |
brain and spinal cord |
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What protects the brain? the spinal cord? |
cranium, vertebral column |
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What makes up the PNS? |
all the nervous system except the brain and spinal cord; composed of nerves and ganglia |
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What is a nerve? |
a bundle of nerve fibers (axons) wrapped in fibrous CT |
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What is a ganglion? |
a knotlike swelling in a nerve where the cell bodies of neurons are concentrated |
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The PNS is divided into ___ and ___ which are each divided into ___ and ___ divisions. |
sensory and motor divisons; somatic and visceral |
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The sensory (afferent) division functions to: |
carry signals from various receptors to the CNS; the pathway that informs the CNS of stimuli in and around the body |
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The somatic sensory divison carries signals from receptors in: |
the skin, muscles, bones, and joints |
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The visceral sensory division carries signals from receptors in: |
the viscera of the throacic and abdominal cavities |
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The motor (efferent) division functions to: |
carry signals from the CNS to the gland and muscle cells that carry out the body's responses |
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Cells and organs that respond to commands from the nervous system are called: |
effectors |
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The somatic motor division carries signals to: |
the skeletal muscles |
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This divison produces muscular contractions that are under voluntary contral, as wella s involuntary muscle contractions called: |
somatic reflexes |
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The visceral motor division (autonomic nervous system) carries signals to: |
glands, cardiac muscle, and smooth muscle |
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The reponses of this system and its effectors are ___ ____. |
visceral reflexes |
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The ANS further divides into: |
the sympathetic division and the parasympathetic division |
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The sympathetic divsion tends to: |
arouse the body for action but inhibits digestion |
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The parasympathetic divsion tends to: |
adapt the body for energy intake and conservation, stimulates digestion but slows down heartbeat |
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The functional unit of teh nervous system is the: |
nerve cell or neuron |
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What are the 3 fundamental physiological properties of neurons that are necessary to communicate: |
Excitability, Conductivity, Secretion |
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What is excitibility/irritability? |
ability to respond to stimuli, nerurons have developed this to the highest degree |
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What is conductivity? |
respond to stimuli by producing traveling electrical signals that quickly reach other cells at distant locations |
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What is secretion? |
when electrical signal reaches end of nerve fiber, neuron usually secretes a neurotransmitter to stimulate next cell |
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What are the 3 general classes of neurons? |
sensory (afferent) neurons, interneurons, and motor (efferent) neurons |
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How are sensory/afferent neurons specialized? |
sepcialized to detect stimuli (light, heath,pressure, chemicals) and to transmit info. about them to CNS |
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What function do interneurons serve? |
lie entirely in CNS, recive signals so they process, store, and retrieve info and "make decisions" about how body responds to stimuli |
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About ___% of human neurons are internuerons. |
90 |
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What role do motor/efferent neurons play? |
send signals to muscle and glad cells, carry out body's responses to stimuli |
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The control center of the neuron is its: |
soma or cell body |
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The soma has __ nucelus/nuclei. |
1 |
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The cytoskeleton of the soma consists of a dense mesh of _____ and ____. |
microtubules and neurofibrils |
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These compartmentalize the rough ER into dark-staining regions called ____ ____, unique to neurons. |
Nissl bodies |
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Nissl bodies are helpful to: |
identify neurons in tissue sections with mixed cell types |
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The major cytoplasmic inclusions in a neuron are: |
glycogen granules, lipid droplets, melanin, and lipofuscin (pushes nucleus to one side) |
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Soma of neuron usually gives rise to a few thick process that branch into a vast number of ____. |
dendrives |
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The dendrites function to; |
receiving signals from other neurons |
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How many dendrites does a neuron have? |
some have one, others have thousands |
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on one side of teh soma is a mound called the __ ___. |
axonal hillock |
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What does the axonal hillock do? |
axon orignates from |
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The axon hillock adn the nearby portino of the axon (initial segment) are collectively the: |
trigger zone b/c this is where teh neuron first generates action potentials |
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What is an action potential? |
electrical changes that constitute the nerve signal |
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What is an axon specialized to do? |
rapid conductino of nerve signals to points remote from the soma |
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The axon may give rise to a few branches called __ ___. |
axon collaterals |
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The cytoplam in an axon is called ____.
The membrane is called the ___. |
axoplasm, axolemma |
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A neuron always/can/never has more than one axon. |
Never has more than one, some neurosn in retina and brain have none. |
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At the distal end an axon usually has a ____ ____ which is an extensive complex of fine branches. |
terminal aborization |
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Each branch of the terminal arborization ends in a __ __. |
synaptic knob |
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What is a synaptic knob? |
a little sweeling that forms a junction/synapse with a muscle cell, gland cell, or another neuron |
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Neurons are classified structurally into 4 categories: |
multipolar, bipolar, unipolar, anaxonic |
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Describe multipolar neurons. |
1 axon, 2+ dendrites
most common type of neuron, most neurons in brain/spinal cord |
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Describe bipolar neurons. |
1 axon, 1 dendrite |
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Describe unipolar neurons. |
one process leading away from soma |
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Where are unipolar neurons found? |
carry sensory signals to spinal cord |
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What are these neurons also called, why? |
pseudounipolar b/c they start out as bipolar neurons in embryo but processes fuse into 1 |
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What are the names of the two fibers, where do they lead? |
peripheral fiber-from sources of sensation
central fiber- continue to spinal cord |
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Describe anaxonic neurons. |
multiple dendrites, no axon
communicate over short distances through dendrites, don't produce action potentials |
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What are the supportive cells of neurons? |
neuroglia or glial cells |
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What are their function? |
protect the neurons and aid their function |
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What are 6 different kinds of glia? |
oligodendrocytes. ependymal cells. microglia. astrocytes. schwann cells. satellite cells. |
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What are oligodendrocytes? |
resemble octopus. wrap around nerve fiber with their processes. in CNS |
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What is the spiral wrapping of an oligodendrocyte called? function? |
myelin sheath, insulates nerve fiber from extracellular fluid and speeds up signal conduction |
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What are ependymal cells? |
resemble cuboidal epithelium lining internal cavities of brain/spinal cord, produce quite a bit of CSF |
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What is CSF? |
clear liquid that pathes CNS and fills its internal cavities |
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What are microglia? |
small macrophages that deveop from monocytes, wanter trhrough CNS and phagocytize foreign matter |
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Where are microglia highly found? |
areas damaged by infection, trauma, or stroke |
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Where are astrocytes found? |
most abundant glia cells in CNS, cover entire brain surface and most nonsynaptic regions of neurons in gray matter of CNS |
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What is the function of astrocytes? |
form supportive framework for NT, form blood/brain barrier, convert blood glucose to lactate and supply to neurons for nourisment |
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What is the function of astrocytes? (part 2) |
secrete protein called nerve growth factors, communicate electrically with neurons and my influence future synaptic signaling between neurons |
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What is the function of astrocytes? (part 3) |
regulate chemical composition of tissue fluid, form hardened scar tissue adn fill space formerly occupied by neurons (sclerosis) |
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Where are Schwann cells found? |
in nerve fibers of PNS |
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What is the function of Schwann cells? |
form a sleeve around fibers called neurilemma, also assist in regeneration fo damaged fibers |
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What are satillate cells? |
surround neuon cell bodies in ganglia of PNS. little is known about their function |
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What is a myelin sheath? |
an insulating layer around a nerve fiber |
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What makes up in myelin sheath in the CNS? in PNS? |
CNS - oligodendrocyte
PNS - Schwann cell |
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What is it composition? |
20% protein, 80% lipid (phospholipids, glycolipids, cholestrol) |
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Myelin imparts a __ color to certain regions of nervous tissue. |
white, like the white matter of the brain and spinal cord |
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Production of the myelin sheath is called: |
myelination |
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The outer layer of the myelin sheath in a Schwann cell is the ____ |
neurolemma |
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what are the gaps between the segments of Schwann cells or oligodendrocytes? |
nodes of ranvier |
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what are the myelin-covered segments from one gap to the next called? |
internodes |
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Many nerver fibers in CNS and PNS are unmyelinated. In the PNS even the unmyelinated fibers are enveloped in Schwann cells. |
yes |
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What 2 factors affect the speed of the signal along a nerve fiber? |
dimater of fiber
prescense/abscense of myelin |
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Singal conduction occurs along surface or deep within axoplam? |
along surface |
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What 2 things are required for regeneration of an axon? |
neurilemma and endoneurium |
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Schwann cells of neurilemma secret __ ___ ___ that stimjulate regrowth of axon. |
nerve growth factors |
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the Schwann cells and endoneurium together form a ___ ___. |
regeneration tube |
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What is the function of the regeneration tube? |
guides growing axon to its destination |
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CNS neurons can/can't regenerate |
can't |
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Since CNS is enclose in ___ it sufferes less traume than the PNS |
bone |
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The meeting point betwen a neuron and any other cell is called a ____. |
synpase |
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Synapses make ____ ____ (information processing) possible. |
neural integration |
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Each synapse is a "decision-making" device that determines where a seconds cell with repons to signals from the first. |
yes |
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The nerve before the synapse is the: |
presynaptic neuron |
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The nerve after the synapse is the: |
postsynaptic neuron |
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A synapse where the presynaptic axon ends at teh dendrite of a postynaptic neuron |
axodendritic synapse |
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A synapse where the presynaptic axon ends on the soma of the next cell |
axosomatic synapse |
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A synapse where the presynaptic axon ends on the axon of the next cell: |
axoaxonic synapse |
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What is a chemical synapse: |
a junction at which the presynaptic neuron releases a neurotransmitter to stimulate the postsynaptic cell |
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What is a common neurotransmitter: |
acetylcholine |
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Some neurotransmitters are ___ and tend to cause the postsynaptic cell to generate a nerve signal. |
excitatory |
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Other neurotransmitters are ___ and suppress responses in the post-synaptic cell. |
inhibitory |
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The terminal branch of the presynaptic nerve fiber ends in a swelling call the ___ ___. |
synaptic knob |
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The knob is separated from the next cell by the __ __. |
synaptic cleft |
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The knob contains membrane-bounded secretory vesicles called ___ ___, which contain ___. |
synaptic vesicles, neurotransmitters |
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Neurotransmitters release through the process of ___. |
exocytosis |
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The membrane of of the postsynaptic neuron is ___. |
folded to increase surface area |
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Another type of synapse, an __ ___, connects some neurons, neuroglia and cardiace and single-unit smooth muscle cells. |
electrical synapse |
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What kind of junctions connect the adjacent cells of an electrical synapse? |
gap junctions |
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What is the advantage of an electrical synapse? |
quick transmission, no delay for release/binding of neurotransmitter |
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What is the disadvantage of an electrical synapse? |
can't integrate info and make decisions |
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Neurons function in ensembles called __ ___. |
neural pools |
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The interconnections btwn neurons are called: __ __ |
neural circuits |
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What are the 4 principle kinds of circuits? |
diverging circuit, converging circuit, reverberating circuit, parallel after-discharge circuit |
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What is a diverging circuit? |
one nerve fiber brances adn synapses with several postsynaptic cells, etc.
1 motor neuron => thousands muscle fibers |
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What is a converging circuit? |
input from many sources is funnel to one neuron or neural pool; contraol breathing rate, lots of sources |
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What is a reverberating circuit? |
neurons stimulate ea. other in line but one sends back to beginning; diapgraphm and intercostal muscle to make inhale; when stops fire exhale |
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What is a parallel after-discharge circuit? |
input neron diverges to stimulate several chains of neurons, eventually all reconverge. sontinued firing after stim. stops |
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Approximately _ in every 100 live-born infants exhibit major defects in brain development. |
1 |
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common among these are ___ ___ ___ such as ___ ___. |
neural tube defects; spina bifida |
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Spind bifida occurs when: |
1 or more vertebrae fail to form a complete neural arch for enclosure of the spinal cord |
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The mildest form is called: |
spina bifida occulta |
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What is spina bifida occulta? |
involves only 1 to a few vertebrae and causes no functional problems |
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What are the external signs of spina bifida occulta? |
dimple or patch of hairy pigmented skin on lower back |
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What is a mroe serious kind of spina bifida? |
spina bifida cystica |
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What is spina bifida cystica? |
a sac protrudes from teh spine and may contain parts of the spinal cord and nerve roots, meninges and CSF |
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What is microcephaly? |
a neural tube defect where the face is of normal size but the brain and calvaria are abnormally small; mental retardation |
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What is anencephaly? |
failure of the rostral end of the neural tube to close, the brain is exposed to the amniotic fluid |
