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 Neurons and Behavior:From Ion Channel to Action

Potential

Christian Kreipke, PhD

ckreipke@med.wayne.edu

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Outline

Nerve Cells and Behavior 

Cytology and Neurons

Synthesis and Trafficking of Neuronal Protein

Ion Channels

Membrane Potential

Local Signaling: Passive Electrical Properties

Action Potential

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 Nerve Cells and Behavior 

Part I

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Two Major types of Cells

Glial Cells

Nerve Cells

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Glial Cells (support)

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Nerve Cell

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There are

Several

Classifications

Of Neurons

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Divergence and Convergence is key

organizational feature

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Inhibitory interneurons produce either 

feedforward or feedback inhibition

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Common features to all Neurons

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Membrane potential

Resting

Potential

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Sensory neurons transform physical

stimuli into electrical activity

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Reflex Action

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Cytology of Neurons

Part II

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Basic Organization

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Example: SensoryMotor 

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Spinal Motor Neurons

Glia

DendritesAxons of spinal motor neurons have branches that make

synaptic contact with several interneurons

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Pyramidal Neurons

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Axons: Insulated by a myelin sheath

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Synthesis and Trafficking

of Neuronal Protein

Part III

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Free and membrane bound

polysomes translate mRNAs

that encode proteins with avariety of destinations 

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Secretory v. transmembrane proteins

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Ion Channels

Part IV

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The ionic

permeability

properties of a

membrane are

determined by

the interactions of 

ions with water,

the membranelipid bilayer, and

ion channels

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Characteristics of Current in a single

ion channel

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Models for the opening and closing of 

ion channels

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Several types of Stimuli control the

opening and closing of ion channels

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Closing a voltage-gated channel

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Ligand binding and receptor kinetics

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Membrane Potential

Part V

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Membran Potential

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Distribution of Major Ions Across a

 Neuronal Membrane  ION [cytoplasm] [extracellular fluid] Equilibrium potential

K+ 400 20 -75

NA+ 50 440 +55

Cl- 52 560 -60

  385Organic ions

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K + flux across the membrane is determined by

[K +] and electrical potential 

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Resting Potential is determined by the relative proportion of open

ion channels with the value of their equilibrium potential 

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Passive Electrical

Properties of a Neuron

Part VI

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Passive conduction of depolarization contributes to

 propagating action potentials 

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Action potentials are regenerated at

 Nodes of Ranvier 

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Propagated Signaling:

The Action Potential

Part VII

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Voltage-gated Na+ channels

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Gating Currents

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Gating is dependent on redistribution

of charge in a very discreet region