PC-505B Manual, Rev. 201013
Warner
Instruments
A Harvard Apparatus Company
49
current-voltage relationship
– A measure of the way in which the current varies as a function of the
applied voltage. In an Ohmic device (obeys Ohm’s law or
V=IR
), this relationship is linear. An
understanding of the current-voltage relationship of
a channel yields information about that channel’s
function.
depolarization
– A biological membrane in which charge separation has resulted in transmembrane
voltage is
termed ‘polarized’. Electrically, depolarization refers to any action which tends to reduce the
degree of polarization. Biophysically, a polarized membrane has a resting transmembrane potential
between
–40 and –90 mV, relative to the inside of the cell. An action which tends to increase the
polarization (e.g., increase the transmembrane potential to, say, -100 mV) is termed hyperpolarization,
while depolarization refers to any action which decreases the transmembrane potential. (It should be
noted that by this definition, a transmembrane potential of +100 mV is still depolarized.)
digital
– Quantized or discrete. Normally refers to information manipulated by a computer. All processes
within a computer are discrete and are composed of 0’s and 1’s. The universe we interact with is
functionally analog, therefore information we wish to manipulate with a computer must be digitized
prior to use by the computer.
DIN connector
– Deutsche Industrie Norm. A German standard for electronic and industrial products. DIN
connectors can be 3 to 6 pin plugs with the same outer diameter and appearance.
electrode
– One terminal of a voltage source which can either supply or collect current.
electromagnetic
– From physics. An electric current induces a magnetic field and a changing magnetic
field induces an electric current. Therefore, these two entities are related to each other and are
combined into electromagnetism.
electrophysiologist
– A scientist who combines the disciplines of physics, electrical engineering, and
physiology to the study biological systems.
Faraday cage
– A grounded conducting enclosure which shields its interior from external electric fields.
Named after Michael Faraday, who first described it in 1875.
gain
– The numerical value of the amplification of a signal by an amplifier. User selectable in the
OUTPUTS
block of the amplifier.
gain telegraph
– A defined voltage dependent on the gain setting appearing at the associated BNC at the
rear of the amplifier. Used to communicate the gain setting to external devices.
ground loop
– A loop formed from multiple connections into the circuit ground plane by the same device.
The flux of magnetic fields through this loop can induce small currents within the ground plane resulting
in increased noise in the circuit. Careful consideration of the interconnection between several devices
is often required to identify ground loops.
headstage
– A low gain amplifier placed as close to the preparation as possible. Used to amplify small
currents to a range sufficient for the main amplifier to accept.
I
m
– A measure of the current passed through an open channel in the presence of a driving force.
Operationally, the current appearing at the Im
OUTPUT
of the amplifier.
intracellular
– Situated or occurring within a cell.
