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Background readings for first week’s lab: Website- Week 1

222 Passive Properties Electrical Terminology Axon Guide Thurman Electric fish pdf

First simulation due Monday, Jan 28 Class participation important Expect assignments on time Review Course policies on Blackboard and Web site

First Lab, Due Monday Feb 4: No formal write-up; Answer questions posed in the lab exercise

Show example figures of your results (resistor ladder graphs, RC circuit responses, electric fish EODs and frequency analysis). Hypothesize the identity of your e-fish- electric fish pdf on web site

January 23, 2013

Figure 16. Electric fish data. One male electric fish was placed in a tank for a 2 minute period at which point a female was inserted. The female has a distinctly higher main frequency component signal compared to the male and the distinction readily appears in the analysis window while other parameters (such as amplitude) may make a relatively unclear clustering. The rate behavior of the only the female discharges may be readily illustrated.0

First Lab: Biological Signals http://crawdad.cornell.edu/gprime/apps/eod1/eod1.html http://crawdad.cornell.edu/gprime/apps/eod2/eod2.html

What aspects of electrical activity in a neuron can be explained by understanding some very basic electrical concepts?

Steady-state Vm determined by Rm. Cm determines time course of voltage changes.

What are the biological representations of the relevant electrical parameters of a neuron?

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Steady-state Vm determined by Rm.

What are some of the different types of membrane channels?

Steady-state Vm determined by Rm.

What are some of the different types of membrane channels? Selectivity?

What other important properties can differentiate channels?

Inactivation kinetics Activation kinetics Opening probability What changes this? What opens (or closes) them? All also changed by neuromodulators

Only a few equations needed in Neurobiology: The separation of unlike charge results in a tendency for an electrical current flow. The extent of current flow depends on the conductance (or its reciprocol, resistance) of the medium separating the charges. What law is this?

Once a channel is open what property does it obey?

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Since R= 1 / G I = V / R V= I / G R = V /I I = V x G G = I / V

Ohm‘s Law V=IR The separation of unlike charge results in a tendency for an electrical current flow. The extent of current flow depends on the conductance (or its reciprocol, resistance) of the medium separating the charges.

How does a separation of specific types of charges come about across a cell membrane?

Current across membrane with hyperpolarizations Im = I Rm + ICm

Ion carrying this ohmic current ?

Current across membrane with strong depolarizations

current no longer ohmic!

Time dependent channel opening

Current across membrane with hyperpolarizations Im = I Rm + ICm

What’s different?

Voltage divider example

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24 V 8 ohm

4 ohm

I = 24/12 = 2A

V= 2 X 8 = 16 V

V=IR I =V/R

Voltage divider rule

+

-

V= 2 X 4 = 8 V

Extracellular

Intracellular

Neurons: 0.01- 1mm

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Changes in Rinput reflect changes in Rm . Calculation of Rinput experimentally from a neuron?? V= IRin Rin= V/I

Steady-state Vm determined by Rm. Cm determines time course of voltage changes.

Membrane Cm

What is a capacitor? C= Q/V What makes a capacitor stronger or weaker? Why does it add time to a voltage change? How does capacitance add in series? How is this relevant to Neurobiology?

Cm = 1 µF/cm2

Neurons: 1 - 20 ms 200 ms in very large cells

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Material basis of thinking

RC circuit Synaptic Integration

Extracellular Recording

Extracellular recording example: Lobster chemoreceptor response

Extracellular recording example: Lobster stomach motor pattern What information is here?