Electrophysiology
Electrophysiology (from Greek ἥλεκτρον,
ēlektron,
"amber" [see the etymology of
"electron"]; φύσις, physis, "nature, origin";
and -λογία, -logia) is the study of the electric-
al properties of biological cells and tissues. It
involves measurements of voltage change or
electric current on a wide variety of scales
from single ion channel proteins to whole or-
gans like the heart. In neuroscience, it in-
cludes measurements of the electrical activ-
ity of neurons, and particularly action poten-
tial activity.
"Current Clamp" is a common technique in
electrophysiology. This is a whole-cell cur-
rent clamp recording of a neuron firing due
to it being depolarized by current injection
Definition and scope
Classical electrophysiological
techniques
Classical electrophysiology techniques
in-
volve placing electrodes into various prepara-
tions of biological tissue. The principal types
of electrodes are: 1) simple solid conductors,
such as discs and needles (singles or arrays),
2) tracings on printed circuit boards, and 3)
hollow tubes filled with an electrolyte, such
as glass pipettes. The principal preparations
include 1) living organisms, 2) excised tissue
(acute or cultured), 3) dissociated cells from
excised tissue (acute or cultured), 4) artifi-
cially grown cells or tissues, or 5) hybrids of
the above.
If an electrode is small enough (micromet-
ers) in diameter, then the electro-physiologist
may choose to insert the tip into a single cell.
Such a configuration allows direct observa-
tion and recording of the intracellular elec-
trical activity of a single cell. However, at the
same time such invasive setup reduces the
life of the cell. Intracellular activity may also
be observed using a specially formed (hollow)
glass pipette. In this technique, the micro-
scopic pipette tip is pressed against the cell
membrane, to which it tightly adheres. The
electrolyte within the pipette may be brought
into fluid continuity with the cytoplasm by
delivering a pulse of pressure to the electro-
lyte in order to rup