Neuroscience, 4e

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Multiple sclerosis - MS Demyelinating disease
of the CNS Can produce sensory and motor
deficits May be an autoimmune disorder
Amyotrophic lateral sclerosis - ALS, Lou
Gehrigs and Stephen Hawkings disease Disease
of motor neurons specifically
Neurodegenerative motor neurons die, muscles
atrophy Only known cause is mutation of SOD1
gene, but this accounts for 1-2 of patients
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Box 3A The Voltage Clamp Technique
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Figure 3.1 Current flow across a squid axon
membrane during a voltage clamp experiment
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Figure 3.2 Current produced by membrane
depolarizations to several different potentials
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Figure 3.4 Dependence of the early inward
current on sodium
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Figure 3.5 Pharmacological separation of Na and
K currents
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Figure 3.6 Membrane conductance changes elicited
in voltage clamp are time- and voltage-dependent
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Figure 3.7 Depolarization increases Na and K
conductances of the squid giant axon
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Figure 3.8 Mathematical reconstruction of the
action potential
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Figure 3.9 Feedback cycles responsible for
membrane potential changes during an action
potential
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Box 3B Threshold
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www.sciencemag.org SCIENCE VOL 287 14 January
2000
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Figure 1
Interneuron dendrites are the sites of synaptic
input and axonal output
reconstruction of filled neuron
electron micrograph
20 µm
axon
0.3 µm
dendrites
biotin-filled dendrite
b1, b2 synapses
soma
50 µm
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Figure 2
Active conductances in dendrites
ITEA / IK total
INa
IK
Axon-bearing dendrite
Axon-lacking dendrite
Soma
INa and IK (pA/µm2)
Distance from soma (µm)
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Figure 4
Active somato-dendritic propagation of action
potentials and boosting of synaptic potentials
A
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Conclusion dendrites can be electrically
excitable and propagate action potentials
www.sciencemag.org SCIENCE VOL 287 14 January
2000