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Outline Neuronal excitability Nature of neuronal electrical signals Convey information over distances Convey information to other cells via synapses Signals.

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Outline Neuronal excitability Nature of neuronal electrical signals Convey information over distances Convey information to other cells via synapses Signals.

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Presentation on theme: "Outline Neuronal excitability Nature of neuronal electrical signals Convey information over distances Convey information to other cells via synapses Signals."— Presentation transcript:

1 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

2 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

3 Figure 2.1 Types of neuronal electrical signals

4 Figure 2.2 Recording passive and active electrical signals in a nerve cell

5 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

6 Figure 2.3 Transporters and channels move ions across neuronal membranes

7 Figure 2.4 Electrochemical equilibrium

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

9 Figure 2.5 Membrane potential influences ion fluxes

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

11 Figure 2.6 Resting and action potentials arise from differential permeability to ions

12

13 Figure 2.7 Resting membrane potential is determined by the K + concentration gradient

14 Box 2A The Remarkable Giant Nerve Cells of Squid

15 Figure 2.8 The role of Na + in the generation of an action potential in a squid giant axon

16 Box 2B Action Potential Form and Nomenclature

17 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

18 Box 3A The Voltage Clamp Technique

19 Figure 3.1 Current flow across a squid axon membrane during a voltage clamp experiment

20 Figure 3.2 Current produced by membrane depolarizations to several different potentials

21 Figure 3.3 Relationship between current amplitude and membrane potential

22 Figure 3.4 Dependence of the early inward current on sodium

23 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

24 Figure 3.5 Pharmacological separation of Na + and K + currents

25 Figure 3.6 Membrane conductance changes underlying the action potential are time- and voltage- dependent

26 Figure 3.7 Depolarization increases Na + and K + conductances of the squid giant axon

27 Figure 3.8 Mathematical reconstruction of the action potential

28 Box 3B Threshold

29 Figure 3.10 Passive current flow in an axon

30 Box 3C(1) Passive Membrane Properties

31 Box 3C(2) Passive Membrane Properties


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