the nervous system - osaka university7 functional properties of the nervous system 1.intensity is...
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The Nervous System
Nobuhiko YamamotoOsaka UniversityGraduate Sch Frontier Biosciences
Basic aspects in the nervous system
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A neuron is composed of axon, dendrite and somata
Diversity of neurons
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Generation and conduction of action potentials
Occurrence of action potentials with sodium and potassium channels
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Extracellular recording
+- -+
EPSP and IPSP
Excitatory postsynaptic potential
inhibitory postsynaptic potential
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+-
EPSC recorded by patch recording
Excitatory postsynaptic current
I = C*dV/dt + V/R
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Ionotropic and Mebotropic receptors
Function of the Brain
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Functional properties of the nervous system1.Intensity is represented by frequency of action potentials
ex, response of retinal ganglion cells to light stimuli, response of motor cortical neurons to force
2.Different modality is processed in different brain region.The presence of visual, auditory, somatosensory, and motor areas
3.Topology is present.ex, retinotopy, somatotopy
4.Reciprocal innervation produces precise control.ex, flexor and extensor
5.Hierarchy of information processing is essential for selective responses.ex. Dotted light stimulus for retinal ganglion cells, more complex visual stimuli for cortical cells
What does firing code?
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Cerebral cortexmotor
association
Somatosensoy
auditory
visual
Broadmann
コラム構造 (columnar structure)
Hubel and Wiesel
Tootel et al., 1982
Macaque retinotopyOcular dominance columnOrientation column
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Body representation
Orientation column
Blasdel
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Optical images in the higher visual cortex
Tanifuji et al., 2001
Myotatic reflex ( Ia afferent)
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Synergists and antagonists
Reflex of cutaneous and deep receptors
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Development of the Brain
Development of Human Brain
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Establishment of neuronal circuitries
cell proliferationmigrationfate determinationaxon outgrowthpath-findingtarget recognitionsynapse formation
Cell division
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Neural stem cells and neuronal cells
影山龍一郎紹介 in 新学術newsletter
proneural gene
nucleus
cytoplasm
neuron
cleavage of cytoplasmic region
neural stem cell
neuralstem cell
neuron
Desai and McConnell, 2000
Cell division and migration
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From John Parnavelas
Cell migration of inhibitory neurons
Cell fate determination
Intrinsic factors(transcriptional factor)
Cell fate
Extrinsic factors(extracellular signals)
Differentiation
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Patterning centers and graded transcription factors drive arealization of the neocortex
O’leary and Sahara, 2008
Fukuchi-Shimogori and Groove, 2001
Electroporatedsite
Neocortex Patterning by the Secreted Signaling Molecule FGF8
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Emx2 expressionHamasaki et al., 2004
Armentano et al., 2007
Axon growth and guidance
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Axon guidance mechanism
Guidance by attractive factors
By repulsive factors
Cellular responsiveness
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Diffusible factors attract growth cones
Commissural axon system
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Semaphorin is involved in the formation of spinal refelex pathway
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Retinotectal projection
posterior
anterior
lateral
medial
nasaltemporal
dorsal
ventral
Fujisawa et al., 1987
Dorsal Lateral Ventral Medial
Retinotopic map formation in the tectum
Temporal Anterior Nasal Posterior
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Stripe assay
Ephrin-Eph system regulates retinotectal projections
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Refinement by neuronal activity
WT
β2 KO
Patterned activity is necessary for fine map formation
McLaughlin et al., 2003
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Sretavan et al., 1988
Neural activity is necessary for pruning of axon branching
Huberman et al., 1988
Neural activity is necessary for segregation of RGC axons in the LGN
P1 P10 P10, epibatidine
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Plasticity
Hippocampus
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Long-term potentiation in hippocampal circuitry
Possibility for postsynaptic mechanisms for LTP
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Hubel and Wiesel, 1962
Ocular dominance column after monocular deprivation
Constantine-paton and Low, 1978
Eye-specific bands are formed by environmental control
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Orientation responsiveness
Axonal branching and synapse formation are inhibited when electrical activity is blocked
Uesaka et al., 2007
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Zuo et al., 2005
Morphology of dendritic spines also changes even in the adult
神経修復と神経再生
Repair and Regeneration
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Christopher Reeve
頚髄における皮質脊髄路の対側への軸索枝形成
0
2
4
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C4 C5 C6 C7 C8
cont
rala
tera
l / ip
sila
tera
l (%
)
42 daycontrol BDA
100μm
injury
CST
cervical spinal cord
BDA BDA
control42 day
**
* *
**
皮質脊髄路の再交叉
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V
VI
VII
VIII
X
BDA
脳損傷後に再交差した皮質脊髄路の枝はlamina VII とVIII に投射する
C4
Propriospinal neuronはlamina VII とVIII に局在する
long
short
0
10
20
30
40
50
60
I-III IV V VI VII VIII IX Xlamina
42day (C4 level)
9週齢で運動皮質切除
3日齢で運動皮質切除
幼い時は代償性神経回路の形成が著明