Lecture 6__neurons And Behavior

Neurons and Behavior: From Ion Channel to Action Potential Christian Kreipke, PhD [email protected]

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

Nerve Cells and Behavior

Part I

Two Major types of Cells  Glial Cells

 Nerve Cells

Glial Cells (support)

 Nerve Cell

 There are

Several Classifications Of Neurons

Divergence and Convergence is key organizational feature

Inhibitory interneurons produce either feedforward or feedback inhibition

Common features to all Neurons

Membrane potential

Resting Potential

Sensory neurons transform physical stimuli into electrical activity

Reflex Action

Cytology of Neurons

Part II

Basic Organization

Example: Sensory  Motor

Spinal Motor Neurons

Glia

Dendrites

Axons of spinal motor neurons have branches that make synaptic contact with several interneurons

Pyramidal Neurons

Axons: Insulated by a myelin sheath

Synthesis and Trafficking of Neuronal Protein

Part III

Free and membrane bound polysomes translate mRNAs that encode proteins with a variety of destinations

Secretory v. transmembrane proteins

Ion Channels

Part IV

The ionic permeability properties of a membrane are determined by the interactions of ions with water, the membrane lipid bilayer, and ion channels

Characteristics of Current in a single ion channel

Models for the opening and closing of ion channels

Several types of Stimuli control the opening and closing of ion channels

Closing a voltage-gated channel

Ligand binding and receptor kinetics

Membrane Potential

Part V

Membran Potential

Distribution of Major Ions Across a Neuronal Membrane ION

[cytoplasm]

K+

400

20

-75

NA+

50

440

+55

Cl-

52

560

-60

Organic ions

385

[extracellular fluid]

Equilibrium potential

K+ flux across the membrane is determined by [K+] and electrical potential

Resting Potential is determined by the relative proportion of open ion channels with the value of their equilibrium potential

Passive Electrical Properties of a Neuron

Part VI

Passive conduction of depolarization contributes to propagating action potentials

Action potentials are regenerated at Nodes of Ranvier

Propagated Signaling: The Action Potential

Part VII

Voltage-gated Na+ channels

Gating Currents

Gating is dependent on redistribution of charge in a very discreet region