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RESEARCH TECHNIQUES
IN NEUROBIOLO​GY
Introduction
Electric charge
• Electrically charged objects experience
mutual force when “close” to each other
• Repulsive forces exist between objects
with the same sign of charge
• Attractive forces exist between opposite
charged objects
Electric potential
• The electrical potential of a location is the
energy that a “basic” charge has there
• The potential difference between two
points is called Voltage
• Voltage has influence on charged objects
5V
5V
10V
• We consider the voltage to be between
two points
Movement of objects
• A charged object pushes or pulls nearby
charged objects
• A pushed object might push the next
object and a chain movement will occur
• A conductor (mediator) is a matter
containing movable charged objects
Electric Conductor
• The potential in a group of (perfect)
attached conductors is one
• Therefore, a (perfect) conductor is an
extension to a point with potential
• This way, the potential can be felt from far
10V
10V
Electric current
• A chain movement of charges is called
Current
• The current moves faster than the objects
• Current can exist only in conductors
• Current can influence
Electric circuit
• An electric circuit is a “continues” chain of
conductors where one end of the chain is
connected to the other
• Circuit + voltage will generate current
• Non perfect conductors resist the current
and slow it – those are resistors
Driving force
• Voltage can be a driving force for current
• Other things can generate current
Electrons current
• The current in artificial systems depends
on electrons – basic negative particles of
atoms
• The conductor is metal in which electrons
can move from one atom to another
Ionic current
• The current in neural systems depends on
ions – electrically charged molecules
• The conductor is a solution with ions
• Voltage is created due to differences of
ionic concentrations
What is the voltage between the inside
and outside of the cell?
Use the electrons or ions?
• The voltage in the preparation is the
potential to move ions
• The computer measures potential to move
electrons
• The medium is different
A combined circuit
• An electric circuit can be combined
• The intersection should be suitable
• A chemical reaction is needed to convert
A solution with ions
• In our case (negative) Chloride ions
Voltage in the solution
• What happens when inserting two metal
wires connected to a battery?
The negatively
charged Chloride
ions will be drawn
to the positive
pole and a
chemical
compound might
be created
Closing the circuit
• Switching between the
poles and adding an
electronic device
• Ions are released from
the negative pole and
push towards the
positive pole
• A chemical reaction
enables current to
continue in the metal
Out of ions
• When the negative
pole is out of ions the
current stops
Switching the poles again
• Switching between
the poles again
reactivates the
current
The voltage is very small and can be
affected by the measurement itself or
changed on the way to the computer
The Voltage
Follower is
close to the
preparation
and can
measure
accurately
without
affecting the
voltage
The
amplifier
can also
inject
current to
stimulate
The
computer
begins to
record a bit
before
there is
stimulation
Noise
• The voltages and currents are tiny
• Parts of the set might become antennas
and insert “noise” to our recording
• To overcome this problem
– Voltage follower close to the preparation
– Isolation of the system
– Connecting everything to the “ground” and thus
direct noise to there instead into our measuring
devices