Outline Neuronal excitability Nature of neuronal electrical signals Convey information over distances Convey information to other cells via synapses Signals depend on changes in electrical potential Resting potential concepts Action potential Properties of action potentials (APs) Dynamics of potential explained by changes in Na+ and K+ permeabilities Voltage clamp (review) Na+ channel activation and inactivation kinetics K+ channel activation (and inactivation) kinetics AP propagation Ion transporters and Ion channels Complementary functions to maintain and use electrochemical gradient Transporters… Generate concentration gradients Channels… Use concentration gradients to make electrical signals
Transcript
Outline
Neuronal excitability
Nature of neuronal electrical signals
Convey information over distances
Convey information to other cells via synapses
Signals depend on changes in electrical potential
Resting potential concepts
Action potential
Properties of action potentials (APs)
Dynamics of potential explained by changes in Na+ and K+ permeabilities
Voltage clamp (review)
Na+ channel activation and inactivation kinetics
K+ channel activation (and inactivation) kinetics
AP propagation
Ion transporters and Ion channels
Complementary functions to maintain and use electrochemical gradient
Transporters…
Generate concentration gradients
Channels…
Use concentration gradients to make electrical signals
Outline
Neuronal excitability
Nature of neuronal electrical signals
Convey information over distances
Convey information to other cells via synapses
Signals depend on changes in electrical potential
Resting potential concepts
Action potential
Properties of action potentials (APs)
Dynamics of potential explained by changes in Na+ and K+ permeabilities
Voltage clamp (review)
Na+ channel activation and inactivation kinetics
K+ channel activation (and inactivation) kinetics
AP propagation
Ion transporters and Ion channels
Complementary functions to maintain and use electrochemical gradient
Transporters…
Generate concentration gradients
Channels…
Use concentration gradients to make electrical signals
Figure 2.1 Types of neuronal electrical signals
Figure 2.2 Recording passive and active electrical signals in a nerve cell
Outline
Neuronal excitability
Nature of neuronal electrical signals
Convey information over distances
Convey information to other cells via synapses
Signals depend on changes in electrical potential
Resting potential concepts
Action potential
Properties of action potentials (APs)
Dynamics of potential explained by changes in Na+ and K+ permeabilities
Voltage clamp (review)
Na+ channel activation and inactivation kinetics
K+ channel activation (and inactivation) kinetics
AP propagation
Ion transporters and Ion channels
Complementary functions to maintain and use electrochemical gradient
Transporters…
Generate concentration gradients
Channels…
Use concentration gradients to make electrical signals
Figure 2.3 Transporters and channels move ions across neuronal membranes
Figure 2.4 Electrochemical equilibrium
Nernst equation
Ek = 58/z * log [K]2/[K]1 = 58 log 1/10 = -58 mV
Figure 2.5 Membrane potential influences ion fluxes
Goldman equation – multiple ionic species and permeabilities
V = 58 log (PK[K]2+PNa[Na]2+PCl[Cl]1
(PK[K]1+PNa[Na]1+PCl[Cl]2
Ek = 58/z * log [K]2/[K]1 = 58 log 1/10 = -58 mV
Reduces to Nernst if only one ion present or permeable…
Figure 2.6 Resting and action potentials arise from differential permeability to ions
Figure 2.7 Resting membrane potential is determined by the K+ concentration gradient
Box 2A The Remarkable Giant Nerve Cells of Squid
Figure 2.8 The role of Na+ in the generation of an action potential in a squid giant axon
Box 2B Action Potential Form and Nomenclature
Outline
Neuronal excitability
Nature of neuronal electrical signals
Convey information over distances
Convey information to other cells via synapses
Signals depend on changes in electrical potential
Resting potential concepts
Action potential
Properties of action potentials (APs)
Dynamics of potential explained by changes in Na+ and K+ permeabilities
Voltage clamp (review)
Na+ channel activation and inactivation kinetics
K+ channel activation (and inactivation) kinetics
AP propagation
Ion transporters and Ion channels
Complementary functions to maintain and use electrochemical gradient
Transporters…
Generate concentration gradients
Channels…
Use concentration gradients to make electrical signals
Box 3A The Voltage Clamp Technique
Figure 3.1 Current flow across a squid axon membrane during a voltage clamp experiment
Figure 3.2 Current produced by membrane depolarizations to several different potentials
Figure 3.3 Relationship between current amplitude and membrane potential
Figure 3.4 Dependence of the early inward current on sodium
Outline
Neuronal excitability
Nature of neuronal electrical signals
Convey information over distances
Convey information to other cells via synapses
Signals depend on changes in electrical potential
Resting potential concepts
Action potential
Properties of action potentials (APs)
Dynamics of potential explained by changes in Na+ and K+ permeabilities
Voltage clamp (review)
Na+ channel activation and inactivation kinetics
K+ channel activation (and inactivation) kinetics
AP propagation
Ion transporters and Ion channels
Complementary functions to maintain and use electrochemical gradient
Transporters…
Generate concentration gradients
Channels…
Use concentration gradients to make electrical signals
Figure 3.5 Pharmacological separation of Na+ and K+ currents
Figure 3.6 Membrane conductance changes underlying the action potential are time- and voltage-dependent
Figure 3.7 Depolarization increases Na+ and K+ conductances of the squid giant axon
Figure 3.8 Mathematical reconstruction of the action potential
