V
A B
100 mM KCl
10 mM KCl
K+ permselective membrane
I
10 mM KCl
100 mM KCl
I
V
I
V
Unpolarizable
electrodes
Electrophysiological
Recordings
-90/-60 mV
0 mV
A cell membrane with a specific permeability and also electrical properties,
channels are proteins in a lipidic environment
Resting Potential
? Ionic Equilibria
i
o
K
K
ZE ][
][ln
F
RT
K ?
?
?
Nernst equation
i
o
K
K
ZF
RT
E
][
][
lnK
?
?
?
Big cylindrical axons
And channel concept
Small myelinated axons
Large neurons
molluscs
motoneurones
Medium size neurons
Small neurons
And other cells
And Channels
~ 1mm
1-5 μm
500 μm
75 μm
< 20 μm
5-10 μm
Metal electrodes
Patch-clamp
Sucrose gap
Glass electrode
recording
K,Cole
1940s
A,Hodgkin
& Huxley
1950s
Hold and Sample
B,Sakmann
And E,Neher
1992
Neuron type Size Technique History
Ling 1949
The voltage clamp
I
V
V command
membrane
5 mM K+
145 Na+
110 Cl-
1 Ca2+
2,Electrical properties of a non-excitable cell,
A resting potential,
leak (background) channels + Na+/K+ ATPase
On the long term,the pump imposes
an assymetrical ionic distribution
Selective permeability to K+
Of the membrane imposes
most of the membrane potential
140 mM K+
4-15 Na+
4-30 Cl-
0.0001 Ca2+
Cell Extracellular
-80/-60 mV
+ osmolarity
Na+/K+ ATPase
Goldman-Hodgkin-Katz equation
oi
oo
K
K
]Cl[P]Na[P][P
]Cl[P]Na[P][Pln
F
RTV
CliNaK
iClNaK
m ???
???
??
???
-90/-60 mV
0 mV
A cell membrane with a specific permeability and also electrical properties,
channels are proteins in a lipidic environment
Experiments Data
NB,On passing current,the ions moving in the cell and in the external
medium is not the same (K and Na respectively)
Experiments Data
Active Ion Pumping
? Na+,K+ -ATPase
? Pump is electrogenic
? K+ equilibrium potential
Action Potential
Nerve Action Potential
Action Potential
The synaptic current is local
Action Potential
Action Potential
? Na+ equilibrium potential
? Na+ Channel
? K+ Channel
Voltage Clamp
Voltage Current
The synaptic current is local
Recording in voltage clamp conditions
Na+ K+
From the currents to the spike
Threshold
Conduction,Velocity
An action potential is all or none!
Patch Clamp
? Single Channel
? Interaction of the Sensory,Motor,and
Motivational Systems is Essential for Even
Simple Behavior
Four Principles
? (1) Relay Centers
? (2) distinct Pathways
? (3) Each Pathway is Topographically
Organized
? (4) Most Pathways Cross the Body’s
Midline
Each System Is composed of
Several Distinct Pathways
? (1) Sensory system
? (2) Motor system
? (3) Motivational system
A B
100 mM KCl
10 mM KCl
K+ permselective membrane
I
10 mM KCl
100 mM KCl
I
V
I
V
Unpolarizable
electrodes
Electrophysiological
Recordings
-90/-60 mV
0 mV
A cell membrane with a specific permeability and also electrical properties,
channels are proteins in a lipidic environment
Resting Potential
? Ionic Equilibria
i
o
K
K
ZE ][
][ln
F
RT
K ?
?
?
Nernst equation
i
o
K
K
ZF
RT
E
][
][
lnK
?
?
?
Big cylindrical axons
And channel concept
Small myelinated axons
Large neurons
molluscs
motoneurones
Medium size neurons
Small neurons
And other cells
And Channels
~ 1mm
1-5 μm
500 μm
75 μm
< 20 μm
5-10 μm
Metal electrodes
Patch-clamp
Sucrose gap
Glass electrode
recording
K,Cole
1940s
A,Hodgkin
& Huxley
1950s
Hold and Sample
B,Sakmann
And E,Neher
1992
Neuron type Size Technique History
Ling 1949
The voltage clamp
I
V
V command
membrane
5 mM K+
145 Na+
110 Cl-
1 Ca2+
2,Electrical properties of a non-excitable cell,
A resting potential,
leak (background) channels + Na+/K+ ATPase
On the long term,the pump imposes
an assymetrical ionic distribution
Selective permeability to K+
Of the membrane imposes
most of the membrane potential
140 mM K+
4-15 Na+
4-30 Cl-
0.0001 Ca2+
Cell Extracellular
-80/-60 mV
+ osmolarity
Na+/K+ ATPase
Goldman-Hodgkin-Katz equation
oi
oo
K
K
]Cl[P]Na[P][P
]Cl[P]Na[P][Pln
F
RTV
CliNaK
iClNaK
m ???
???
??
???
-90/-60 mV
0 mV
A cell membrane with a specific permeability and also electrical properties,
channels are proteins in a lipidic environment
Experiments Data
NB,On passing current,the ions moving in the cell and in the external
medium is not the same (K and Na respectively)
Experiments Data
Active Ion Pumping
? Na+,K+ -ATPase
? Pump is electrogenic
? K+ equilibrium potential
Action Potential
Nerve Action Potential
Action Potential
The synaptic current is local
Action Potential
Action Potential
? Na+ equilibrium potential
? Na+ Channel
? K+ Channel
Voltage Clamp
Voltage Current
The synaptic current is local
Recording in voltage clamp conditions
Na+ K+
From the currents to the spike
Threshold
Conduction,Velocity
An action potential is all or none!
Patch Clamp
? Single Channel
? Interaction of the Sensory,Motor,and
Motivational Systems is Essential for Even
Simple Behavior
Four Principles
? (1) Relay Centers
? (2) distinct Pathways
? (3) Each Pathway is Topographically
Organized
? (4) Most Pathways Cross the Body’s
Midline
Each System Is composed of
Several Distinct Pathways
? (1) Sensory system
? (2) Motor system
? (3) Motivational system
