Flashcards in Neurons: Lec 2 Deck (135)
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1
Neurons
information processors
2
Glial Cells
Scaffolding and support services and communication facilitators
3
Anatomy of a neuron
Cell body/ soma/ perikaryon
Dendrites
Axon
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components of the cell body/soma/perikaryon
nucleus, organelles, mitochondria, golgi apparatus, cytoskeleton, microtubules, neurofiliments
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components of the dendrites
dendritic tree
dendritic spines
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components of the axon
axon hillock
initial segment
node of ranvier
terminal button
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Oligodendrocytes are myelin cell for what system
central nervous system
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oligodendrocytes are multiple axons to 1 what
cell
9
Schwann cells are myelin cells for what system
PNS
10
schwann cells are multiple cells to 1 what
axon
11
schwann cells are speed what?
synaptic transmission
12
types of glial cells
oligodendrocytes
schwann cells
astrocytes
13
Astrocytes
star shaped cytoskeletal cells
14
three types of astrocytes
Protoplasmic
fibrous
radial
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what are protoplasmic astrocytes
gray matter
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what are fibrous astrocytes
white matter
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what are radial astrocytes
development guide cells
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Roles of the astrocytes
-structural support
-Blood brain barrier
-scar formation
-nutrient transport
-release glutamate (neurotransmitter)
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unipolar
one cell process
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example of unipolar cells
spinal ganglia
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Bipolar
two cell processes
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functions of bipolar
sensory
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example where bipolar cells are
retina
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Multipolar
> 2 dendrites. many dendrites and 1 axon
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Multipolar transmit what
sensory and motor
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What systems are mostly composed of multipolar cells
CNS & PNS
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pseudounipolar
afferent and efferent
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afferent
takes info from environment to CNS
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Efferent
takes information from CNS to muscles, glands
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Ganglion/ ganglia
collection of cell bodies
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Projection fibers
axon that travel up and down the CNS
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Association fibers
axon that connect one lobe to another
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commissural fibers
axon running between the hemispheres
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Internuncial neurons
transmit AP from one neuron to another
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Gray Matter
collections of nerve cell bodies
unmylinated fibers
dendtries found in CNS
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white matter
collections of mylinated fibers
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Fasiculas
small bundle of myelinated fibers
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Fasiculas is synonym for what
tract in certain spinal cord sections
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funiculus
"a little cord" composed of several fasiculi
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funiculus differentiate what
dorsal, lateral and ventral funiculi
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Brachium
"arm" thick bundle of fibers connecting one part of the brain to the other
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what are synaptic triggers of action potential
-mechanical
-thermal
-chemical
-light
-electrical
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the 3 things of a basic synaptic transmission
1. stimulus causes change in electrical potential of cell
2. threshold is reached and AP travel down axon
3. Terminal endings release chemicals that cause depolarization of next dendritic tree or cell body
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Axon hill is the what of transmissions
gatekeeper
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All or none phenomena
once AP fires, it is equal throughout length of axon
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myelinated axons transmitted what than non myelinated
faster
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fatter or skinner axons are faster?
fatter
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voltage sensitive channels collect where
nodes of ranvier
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voltage sensitive channels collect at nodes of ranvier, facilitating what?
saltatory conduction
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Electrical potential as the basis for what?
synaptic transmission
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at resting potential the cell membrane is what ?
semipermeable
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synaptic/ receptor potentials are small areas of
depolarization
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Depolarization
> 15 mV change required causing a rush of Na+ into channels
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Action potential propagation continues until when
all channels are opened (cell becomes -50mV)
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when does repolarization happen?
resting potential is reestablished
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what is not possible during repolarization?
action potential
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Characteristics of ion channels in cell membranes
multiple states
gating
selectivity for types and sizes of ions
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at multiple states channels can be
either open or closed
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voltage gate channels respond to
voltage changes
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ligand gated channels respond to
signal molecules that land on binding sites
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thermal gated channels respond to
temperature changes
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mechanically gated channels respond to
deformation
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selectivity for types and sizes of ions depend on what/
size of channel and type of molecular lining
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absolute refractory period
intracellular charge reaches +30 - +50 mV and all Na+ channels are closed. No AP possible during this time
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Relative refractory Period
both Na+ and K+ channels are closed causing hyper polarization .
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During relative refractory period was cause a AP
MORE stimulus
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Factors that affect transmission speed
-myelination
-axon diameter (larger faster)
-temp of limb (cold slow)
-age (>4 - faster)
-disease (demyelinating slow)
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amines
small molecules / neurotransmitters
69
examples of amines
acetylcholine, catecholamines (dopamine, norepinphrine) serotonin, histamine
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Amino acids
1-10 amines
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examples of amino acids
glutamate, GABA, Glycine
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Neuropeptides
large amino acid clusters
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examples of neuropeptides
angiotensin II, B-endorphin, Cholecystokinin, corticotropin releasing factor, substance P, Enkephalin
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Amines are creased in
presynaptic cytoplasm
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Peptides are created in
cell body
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Nicotinic receptors on the cell yield excitatory effect in
response to acetylcholine
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Muscarinic receptors yield inhibitory effect in ?
response to acetylcholine
78
Acetylcholine can be what depending on the receptors
-Excitatory or inhibitory
79
Acetylcholine on skeletal muscles has what effect
excitatory
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Acetylcholine on smooth and cardiac muscle has what effect
inhibitory
81
neurons communicate by what
chemical transmitters that cause electrical potentials
82
When does the nervous system begin to evolve
week 3
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when does the bilaminar disc form from which nervous system will form?
14 days
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When is their implantation ?
week 2
85
when is there further development of you sac,amnion and embryonic disc?
week 2
86
Primitive streak and groove appear where and when
in the ectoderm and week 3
87
when is there neural tube formation ?
week 3
88
Neural crest become
sensory & ANS ganglia
glands
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Neural tube becomes
CNS, epidermis, tooth enamel
90
Notochord becomes
nucleus propulsus
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Dermatome becomes
subcutaneous skin, sensory
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Myotome becomes
dorsal spinal muscles
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Sclerotome becomes
vertebral column & ribs
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when does neural tube folding begin
week 4
95
What are the Neural tube layers
-epitheial layer
-Mantle layer
-Marginal layer
-Dorsal/alar plate
-ventral/ basal plate
-Intermediare zone
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Gliablasts or spongioblasts (epithelial layer) becomes
-ependymal cells
-astrocytes
-oligodendrocytes
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mantle layer becomes
gray matter
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mantle layer sends what
neuronal process outward
99
marginal layer becomes
white matter following myelination
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What functions does the dorsal / alar plate have
sensory
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what functions does the ventral/ basal plate have
motor
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What functions does the intermediate zone have
autonomic
103
what happens at week 5
cephalic folds
limbs buds appear
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what happens at week 6
Eye
UE elbow-hand
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What happens at week 7
acoustic meat
UE digits
foot plate
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Prosencephalon split into
telencephalon & diencephalon
107
Telencephalon becomes what
cerebral hemispheres, corpus striatum, cortex + medullary center of white matter
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Diencephalon becomes what
thalamus, epithalamus, hypothalamus and sub thalamus
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Mesencephalon becomes
midbrain
110
Rhombencephalon divides into
metencephalon & Myelencephalon
111
Metencephalon becomes
pon & cerebellum
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Myelencephalon becomes
Medulla oblongata
113
What happens at week 8?
facial features begin to form, UE and LE joints and digits have differentiated.
abdominal cavity is not complete
tail is not obvious
114
week 9-38 are considered
fetal period
115
When is a baby most vulnerable to teratogenic influences
first 2 months
116
Anencephaly
rostral neuropore does not close in 4th week
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Spina bifida occulta
caudal neuropore does not close in 4th week, vertebral arches do not fuse
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Meningocele
dural sack extrudes but no spinal nerve included
119
Meningomyelocele
portions of spinal cord displaced into extruding dural sack
120
Cleft palate
lack of midline closure during 6-12 weeks
121
plagiocephaly
asymmetrical skull shape
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Brachycephaly
when baby lays on back all the time
123
Neonatal Neuronal Exuberance
-greater # of neurons are created than needed
-duplication of synaptic pathways is plentiful during development
-Synaptic connections multiply quickly
-selected cells become dormant if not used
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Neurotophism
changes occur from the interaction of synaptically connected cells
125
during neurotophism what happens to dendrites, axon and synaptic vessel
dendritic spine proliferation
axonal myelination
synaptic vesicle development
126
What happens when neurons do not get stimulation
degrad, die or go dormant
127
What happens to cells that do not connect with enough other cells
do not receive the neurotrophic stimuli to mature
128
paring in the NS may help what
streamline communication
129
Dormant cell may be used at a later time if what happens
stimulation
130
What is neural plasticity
ability of CNS to create new pathways
131
what increases synaptic activity in the cortex and in periphery
practicing a skill
132
During an injury, what takes over for damaged tissue
adjacent cortical tissue
133
During injury, what is done to accomplish the same functional result
development of new pathways
134
what excites neurons
stimulation
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