Applied Sciences

Conductivity of strong and weak electrolytes (with the Cobra3 Basic-Unit)

Principle

It is possible to differentiate between strong and weak electrolytes by measuring their electrical conductance. Strong electrolytes follow Kohlrausch's law, whereas weak electrolytes are described by Ostwald's dilution law. The examination of the concentration depen ...

Determination of diffusion potentials

Principle

An electrochemical potential establishes itself at the interface between two solutions of different ion concentrations. The magnitude of this is determined by the concentration ratio and the transference numbers of ...

Absorption of light (UV-VIS spectroscopy)

Principle

The structures of molecules are not changed by their chemical environment in the gas phase. In contrast to this, on transition to the condensed phase, in dilute solution, the solvent changes the binding state of the dissolved substance. One of the way this influence ...

Excitation of molecules

Principle

The position of the longest wavelength π - π* -absorption band in the UV-visible spectrum of organic compounds which have chromophoric systems can be approximately calculated by various methods. For dyes with extended conjugated π-systems, the model of the ...

Absorption spectra and pKa values of p-methoxyphenol

Principle

For weak acids HA, the position of the K_a and pK_a values that characterize the dissociation equilibrium in the ground state can be determined from photometric measurements in solutions having different pH values. Further to this, ...

Recording of nerve and muscle potentials by mechanical stimulation at the rear end of an earthworm (Cobra3)

Principle and tasks

To work on the following themes by measuring nerve and muscle potentials:

• the course of a biphasic action potential over time
• estimation of the conduction velocity
• coding of the stimulant intensity as frequency modulation ...

Recording of nerve and muscle potentials by mechanical stimulation at the front end of an earthworm (Cobra3)

Principle and tasks

To work on the following themes by measuring nerve and muscle potentials:

• The difference in sensitivity of the front and rear ends
• The facilitation effect
• Conduction velocity and fibre diameter
• Synaptic depress ...

Recording of nerve potentials after the electrical stimulation of an anaesthetised earthworm (with the Cobra3 Basic-Unit

Principle and tasks

To work on the following themes by measuring nerve and muscle potentials:

• The action of an anaesthetic
• The different conduction velocities of median and lateral giant fibres
• Refractory period of the median giant fibre

Model experiment illustrating the development of resting potential (with Cobra4)

Principle and tasks

The potential difference between two electrolyte concentrations separated by a membrane (cellophane or cation permeable) is detected by two silver chloride electrodes and measured with a mV meter. The measured and calculated values are compared.

Neurosimulator: membrane time constant and low-pass filte-ring (with the Cobra3 Basic-Unit)

Principle and tasks:

To use a nerve function model to work onthe following themes:

• The time constant of the nerve membrane and intracellular potential
• The low-pass characteristic of the nerve membrane

What you can le ...

Neurosimulator: mode of operation of excitatory synapses (with the Cobra3 Basic-Unit)

Principle and tasks

To use a nerve function model to work on the following themes:

• The origin of action potentials
• The transformation of stimulation intensity to action potential frequency

What you can learn about

Neurobiology: the nerve cell

Principle and tasks

To use a nerve function model to study the following aspects of a nerve cell: intercellular potential and actionpotential.

What you can learn about

• Comparison between low and high threshold levels
• Comparison b ...

Neurobiology: nerve cell interactions

Principle

To use a nerve function model to study the following aspects of nerve cell interactions with other nerve cells or with motoric and sensoric cells:

Renshaw inhibtion

• Motoneuron signals wit ...

Neurobiology: neural networks

Principle, tasks and what you can learn about:

To use a neve function model to study the following aspects of neural networks:

TRANSIENT (PHASIC) RESPONSES: FOCUS ONVISUALSENSE

• Transient responses: ON neu ...

Neurobiology: complex neural networks

Principle, tasks and what you can learnabout

To use a nerve function model to studythe following aspects of neuralnetworks:

• Direction selectivity by unilateralinhibition
• Self-calibration of paired sensorychannels