8/20/2019 LEB01_05

1/314 PHYWE Systeme GmbH & Co. KG · D-37070 GöttingenLaboratory Experiments, Biology

Nervous System LEB 01

01.05 Neurosimulator: Membrane time constant and low-pass filtering

Principle and tasks:To use a nerve function model towork on the following themes:● The time constant of the nerve

membrane and intracellular po-tential

● The low-pass characteristic of thenerve membrane

Result of a single stimulation

What you can learn about

Time constant of nerve mem-brane

Intracellular potential

Low-pass characteristic

Cobra3 Basic Unit 12150.00 1

Power supply, 12 V 12151.99 1

RS232 data cable 14602.00 1Cobra3 Universal Recorder software 14504.61 1

Neurosimulator 65963.00 1

Neurosimulator, power supply 65963.93 1

Connecting cord, 500 mm, yellow 07361.02 1

PC, Windows® 95 or higher

What you need:

Neurosimulator: Membrane time constantand low-pass filtering P4010511

Result of a succession of stimulations

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2/3Phywe Series of publication • Laboratory Experiments Biology • © PHYWE SYSTEME GMBH & Co. KG • D-37070 Göttingen 40105 21

LEB01.05

Neurosimulator:Membrane time constant and low-pass filtering

Related topicsTime constant of nerve membrane, intracellular potential,low-pass characteristic

Principle and taskTo use a nerve function model to work on the followingthemes:• The time constant of the nerve membrane and intracel-

lular potential• The low-pass characteristic of the nerve membrane

EquipmentCobra3 Basic Unit 12150.00 1Power supply, 12 V 12151.99 1RS232 data cable 14602.00 1Cobra3 Universal Recorder software 14504.61 1

Neurosimulator 65963.00 1Neurosimulator, power supply 65963.93 1Connecting cord, 500 mm, yellow 07361.02 1PC, Windows ®

Set-up— Connect the instruments as shown in Fig. 1.

— Power supply for the neuro-simulator: 9 V out to 9 Vin (three-pin cable)

— Propagation of stimulus: Stimulus output 1 to stimula-tory synapse (short white cable)

— Intracellular potential: Output 1 to Analog in 1 (yellowcable)

— Stimulating signal: Stimulus output 1 to Analog in 2(yellow cable), Earthing socket to Analog in 2 (longwhite cable)

Procedure— Call up the COBRA 3 M EASURE programme in Windows— Select the UNIVERSAL WRITER as measuring instrument— Use the rotary knob S of the neuro-simulator to adjust

the threshhold value to the smallest value (turn to theleft stop)

— Set stimulation channel 1 of the power supply to max-imum stimulation (turn to the right stop)

— Set the measurement parameters (see Fig. 2) and goto measurement with C ONTINUEExperiment 1:

— Briefly tip the switch of stimulation channel 1; save theresult

Fig. 1: Experimental set-up

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Experiment 2:— Click on the red point and go to measurement with

C ONTINUE— Tip the switch of stimulation channel 1 repeatedly and

at increasingly shorter intervals; save the result

Results and evaluation— Experiment 1: When the neuro-simulator is excited by

a rectangular pulse from a synapse, the intracellularpotential only increases slowly, and then falls off evenslower when the stimulation stops (Fig. 3). As a resultof this behaviour, rapid and brief stimulating signalscan only be weakly transmitted (low-pass characteris-tic of the membrane)

— Experiment 2: When short rectangular impulses act atrelatively large intervals, the intracellular potential can

follow the stimulating pulse frequency (Fig. 4). Thelow- pass characteristic of the membrane allows theconversion of the low frequencies to a response.When the stimulating frequency is higher, the intracel-lular potential reaches an almost constant value.Individual rectangular stimulations then no longercause a separate response of the membrane.

Note— Many further experiments can be carried out in a sim-

ilar way using 1, 2, 3 or 4 neurosimulators (see the“Operating Instructions”).

Phywe Series of publication • Laboratory Experiments Biology • © PHYWE SYSTEME GMBH & Co. KG • D-37070 Göttingen4010522

LEB01.05

Neurosimulator:Membrane time constant and low-pass filtering

Fig. 2: Measurement parameters

Fig. 3: Result of a single stimulation

Fig. 4: Result of a succession of stimulations