Outline Neuronal excitability Nature of neuronal electrical signals Convey information over...

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

Box 3B Threshold

Figure 3.10 Passive current flow in an axon

Box 3C(1) Passive Membrane Properties

Box 3C(2) Passive Membrane Properties