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 neuro4e-fig-02-01-0.jpg

Figure 2.2 Recording passive and active electrical signals in a nerve cell neuro4e-fig-02-02-0.jpg

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 neuro4e-fig-02-03-0.jpg

Figure 2.4 Electrochemical equilibrium neuro4e-fig-02-04-0.jpg

Ek = 58/z * log [K]2/[K]1 = 58 log 1/10 = -58 mV Nernst equation Ek = 58/z * log [K]2/[K]1 = 58 log 1/10 = -58 mV

Figure 2.5 Membrane potential influences ion fluxes neuro4e-fig-02-05-0.jpg

Goldman equation – multiple ionic species and permeabilities (PK[K]2+PNa[Na]2+PCl[Cl]1 V = 58 log (PK[K]1+PNa[Na]1+PCl[Cl]2 Reduces to Nernst if only one ion present or permeable… Ek = 58/z * log [K]2/[K]1 = 58 log 1/10 = -58 mV

Figure 2.6 Resting and action potentials arise from differential permeability to ions neuro4e-fig-02-06-0.jpg

neuro4e-table-02-01-0.jpg

Figure 2.7 Resting membrane potential is determined by the K+ concentration gradient neuro4e-fig-02-07-0.jpg

Box 2A The Remarkable Giant Nerve Cells of Squid neuro4e-box-02-a-0.jpg

Figure 2.8 The role of Na+ in the generation of an action potential in a squid giant axon neuro4e-fig-02-08-0.jpg

Box 2B Action Potential Form and Nomenclature neuro4e-box-02-b-0.jpg

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 neuro4e-box-03-a-0.jpg

Figure 3.1 Current flow across a squid axon membrane during a voltage clamp experiment neuro4e-fig-03-01-0.jpg

Figure 3.2 Current produced by membrane depolarizations to several different potentials neuro4e-fig-03-02-0.jpg

Figure 3.3 Relationship between current amplitude and membrane potential neuro4e-fig-03-03-0.jpg

Figure 3.4 Dependence of the early inward current on sodium neuro4e-fig-03-04-0.jpg

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 neuro4e-fig-03-05-0.jpg

Figure 3.6 Membrane conductance changes underlying the action potential are time- and voltage-dependent neuro4e-fig-03-06-0.jpg

Figure 3.7 Depolarization increases Na+ and K+ conductances of the squid giant axon neuro4e-fig-03-07-0.jpg

Figure 3.8 Mathematical reconstruction of the action potential neuro4e-fig-03-08-0.jpg

Box 3B Threshold neuro4e-box-03-b-0.jpg

Figure 3.10 Passive current flow in an axon neuro4e-fig-03-10-0.jpg

Box 3C(1) Passive Membrane Properties neuro4e-box-03-c(1)-0.jpg

Box 3C(2) Passive Membrane Properties neuro4e-box-03-c(2)-0.jpg