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Biologa. (2007). Campbell, N. A. y
Reece, J.B. Sptima edicin. EditorialMdica Panamericana.
Madrid
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LE 48-9
Microelectrode
Referenceelectrode
Voltagerecorder
70 mV
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LE 48-10
CYTOSOL EXTRACELLULARFLUID
[Na+]15 mM
[K+]
150 mM
[A]100 mM
[Na+]150 mM
[K+]5 mM
[Cl]120 mM
[Cl]10 mM
Plasmamembrane
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LE 48-11
150 mM
KCl
Innerchamber
Outerchamber
92 mV
Potassiumchannel
Membrane selectively permeable to K+ Membrane selectively
permeable to Na+
5 mM
KCl
Artificialmembrane
K+Cl
150 mM
NaCl
Innerchamber
Outerchamber
+62 mV
Sodiumchannel
15 mM
NaCl
Na+
Cl
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LE 48-13_1
Resting potential
Threshold
M
embranepotential
(mV)
Actionpotential
Time100
50
+50
0
Potassium
channel
Extracellular fluid
Plasma membrane
Na+
Resting state
Inactivationgate
Activation
gates
Sodiumchannel
K+
Cytosol
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LE 48-13_2
Resting potential
Threshold
M
embranepotential
(mV)
Actionpotential
Time100
50
+50
0
Potassium
channel
Extracellular fluid
Plasma membrane
Na+
Resting state
Inactivationgate
Activation
gates
Sodiumchannel
K+
Cytosol
Na+
Depolarization
K+
Na+
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LE 48-13_3
Resting potential
Threshold
Membrane
potential
(mV
)
Actionpotential
Time100
50
+50
0
Potassiumchannel
Extracellular fluid
Plasma membrane
Na+
Resting state
Inactivationgate
Activationgates
Sodiumchannel
K+
Cytosol
Na+
Depolarization
K+
Na+
Na+
Rising phase of the action potential
K+
Na+
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LE 48-13_4
Resting potential
Threshold
Membrane
potential
(mV
)
Actionpotential
Time100
50
+50
0
Potassiumchannel
Extracellular fluid
Plasma membrane
Na+
Resting state
Inactivationgate
Activationgates
Sodiumchannel
K+
Cytosol
Na+
Depolarization
K+
Na+
Na+
Rising phase of the action potential
K+
Na+
Na+
Falling phase of the action potential
K+
Na+
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LE 48-13_5
Resting potential
Threshold
Membrane
potential
(mV
)
Actionpotential
Time100
50
+50
0
Potassiumchannel
Extracellular fluid
Plasma membrane
Na+
Resting state
Inactivationgate
Activationgates
Sodiumchannel
K+
Cytosol
Na+
Depolarization
K+
Na+
Na+
Rising phase of the action potential
K+
Na+
Na+
Falling phase of the action potential
K+
Na+
Na+
Undershoot
K+
Na+
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LE 48-14a
An action potential is generated as Na+flows inward acrossthe
membrane at one location.
Na+
Actionpotential
Axon
LE 48 14b
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LE 48-14b
An action potential is generated as Na+flows inward acrossthe
membrane at one location.
Na+
Actionpotential
Axon
Na+
ActionpotentialK+
The depolarization of the action potential spreads to
theneighboring region of the membrane, re-initiating the
actionpotential there. To the left of this region, the membrane
isrepolarizing as K+flows outward.
K+
LE 48 14
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LE 48-14c
An action potential is generated as Na+flows inwardacross the
membrane at one location.
Na+
Actionpotential
Axon
Na+
ActionpotentialK+
The depolarization of the action potential spreads to
theneighboring region of the membrane, re-initiating theaction
potential there. To the left of this region, themembrane is
repolarizing as K+flows outward.
K+
Na+
ActionpotentialK+
The depolarization-repolarization process is repeated in thenext
region of the membrane. In this way, local currents ofions
acrossthe plasma membrane cause the actionpotential to be
propagated alongthe length of the axon.
K+
LE 48 15
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LE 48-15
Cell body
Schwann cell
Depolarized region(node of Ranvier)
Myelinsheath
Axon
LE 48 16
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LE 48-16
Postsynapticneuron
Synapticterminalsof pre-synaptic
neurons
5m
LE 48 17
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LE 48-17
Postsynaptic cellPresynapticcell
Synaptic vesicles
containing
neurotransmitter
Presynaptic
membrane
Voltage-gated
Ca2+channelCa2+
Postsynaptic
membrane
Postsynapti
membrane
Neuro-
transmitter
Ligand-gated
ion channel
Na+K+
Ligand-gated
ion channels
Synaptic cleft
LE 48 18
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LE 48-18
Postsynapticneuron
Terminal branchof presynapticneuron
E1 E1
Axon
hillock
E1E2
E1
I
Action
potential
E1E1+ E2
Spatial summationof EPSP and IPSPSpatial summation
I E1+ I
Action
potential
E1
Temporal summation
E1
Threshold of axon of
postsynaptic neuron
E1
Subthreshold, nosummation
E1
Resting
potential
Membranepotential(mV)
70
0
