EXAM 2 Flashcards
electrophysiology
the recording of voltages between reference points in or near cell by using a probe to stimulate or measure
How does an electrophysiology rig work?
An electrical signal is recorded by a microelectrode and passed along to an amplifier. The amplifier compares the recording to a ground electrode, and then passes along the signal to an oscilloscope and/or computer.
oscilloscope
presents a visual display of the membrane potential over time, which can also be heard using a loudspeaker
Why are glass pipettes necessary for patch clamp recordings?
because they can create tight seals
How many electrodes are needed for any electrophysiology recording?
2, the recording electrode itself and a ground electrode for reference because an electrophysiology measurement is a comparison
amplifier
enhances the relatively weak electrical signal from an FM antenna and receives info from the ground electrode
Why are loudspeakers used in electrophysiology?
they can pick up changes in voltage over time because they can hear neurons
Why is a vibration isolation system (air table) used?
to absorb tiny changes in vibration that can disturb the placement of the microelectrode
Faraday cage
blocks external electrical interference to eliminate noise from sensitive electrical recording that can detect external electrical activity
I/V curve
a plot of the voltage across a neuronal membrane and the associated ionic current flow through channels in the membrane
What axis is the voltage on in the I/V curve?
x-axis
What axis is the current on in the I/V curve?
y-axis
How is an I/V curve produced?
a voltage clamp is used to hold the voltage of a neuron at a specific value and then current can be recorded using one of the patch clamp methods
Currents with a (-) value are __.
inward currents; cations coming into the cell
Currents with a (+) value are __.
outward currents; anions coming into the cell
Non-voltage dependent channels are ___ channels.
independent
magnification
how much larger the sample appears compared to its actual size
resolution
the minimum distance by which two points can be separated yet still be distinguishable as two separate points
numerical aperture
a measure of the light-collecting ability of the microscope objective
What does a higher numerical aperture mean?
more light rays collected, leading to better resolution
What does the numerical aperture of an objective depend on?
the angle that light enters the objective and the index of refraction of the medium in which the objective is working
index of refraction (refractive index)
indicates changes in the speed of light traveling through a particular medium
What does a greater index of refraction mean?
the greater the index of refraction, the greater the numerical aperture
What does the slope of the tracing in an I/V curve mean?
it indicates the resistance of the channel (or conductance)
What does a greater slope mean?
it indicates more charges per unit time passing through the channel for a given voltage
