Electrical properties of neurons

Gilad Silberberg

Different types of neurons in the different structures of the nervous system

The nervous system: Elaborate

And vulnerable…

Structural diversity in the nervous system demonstrated with markers.

Electrical Properties of Neurons

Common Features:

• Membrane potential & ion channels

• Passive membrane properties

• Voltage-dependent (active) membranes

1.2 Examples of the rich variety of nerve cell morphologies found in humans. (Part 3)

2.2 Recording passive and active electrical signals in a nerve cell. (Part 1)

2.2 Recording passive and active electrical signals in a nerve cell. (Part 2)

2.3 Ion transporters and channels are responsible for ionic movements across membranes.

The membrane as a charge separator

2.4 Electrochemical equilibrium. (Part 1)

2.4 Electrochemical equilibrium. (Part 2)

Nernst Potential

Example for Potassium:

2.5 Membrane potential influences ion fluxes. (Part 2)

2.5 Membrane potential influences ion fluxes. (Part 3)

Different ions determine the membrane potential

Circuit representation:

Different ions determine the membrane potential

Different ions determine the membrane potential

Which ion is dominant?

The Goldman equation

Another version of the same thing:

2.7 Evidence that the resting potential is determined by K+ concentration gradient. (Part 1)

2.4 Electrochemical equilibrium. (Part 2)

Next:

Properties of ion-channels

Ion Channels

• Specialized membrane proteins that

traverse the cell membrane

• Conduct ions

• Recognize and select among specific ions

• How?

Transporters vs. Channels

Control of Ions Flux through Ion

Channels

• The flux of ions is passive, i.e., does not

require energy

• The direction of ions flux is not determined by

the channel

• The direction of ions flux is determined by the

electro-chemical driving force

Two Classes of Ion ChannelsTwo Classes of Ion Channels

• Non-gated ion channels

» Always open

» Leak channels

» Maintain the resting membrane potential

• Gated ion channels

» Open and close in response to a specific stimulus

» Transition between closed and open states = Gating

» Synaptic potentials, Action potentials

Gated Ion Channels

Type of channel Stimulus Effect

Ligand-gated Transmitter substance Directly gated synaptictransmission

Phosphorylation-gated Phosphorylation 2nd

messenger-mediatedsynaptic transmission

Voltage-gated Change in membranepotential

Generation of actionpotential

Stretch or pressure-gated Mechanical deformationof the membrane

Generation of receptorpotential in mechano-receptors

Example of the Patch-Clamp technique

Summary

• Ion channels are:

• Specialized membrane proteins

• Conduct ions

• Recognize and select among specific ions

• Subdivided into two classes: non-gated and

gated channel