Lec 5 & 6 Flashcards
A small number of ions will change the Vm by Alot!
T or F?
True
What is defined as “a measurement of cell voltage while controlling applied current “ ?
Current Clamp
What is defined as “a measurement of cell currents hwile controlling cell voltage “ ?
Voltage Clamp
Which “Clamp” experiment is being described?
When current is injected, capacitance causes a delay in voltage response in order to charge the membrane.
Current Clamp
Capacitance (in Voltage Clamp) depends on what two variables?
size of the cell
and
size of voltage change
Which “Clamp” experiment is being described?
When cell voltage ‘steps up’ there is a transient burst of current.
The equal but opposite current that occurs when the membrane is returned to original voltage is dissipated.
Voltage Clamp
Which 2 people discovered the Patch Clamp Technique?
Erwin Neher + Bert Sakmann
What “enables recordings of the opening and closing of individual ion channels” ?
*high resistance seal*
Patch Clamp Technique
What are the 4 types of Patch Clamp Configurations?
- cell-attached
- whole-cell patch
- inside-out excised patch
- outside-out excised patch
What is “The cell-attached patch clamp technique” ?
Channels remain on the cell surface - single channel recording
What is “The whole-cell patch clamp technique” ?
enables recording of all currents on the cell membrane
(broken open to cell membrane)
What is “The inside-out excised patch clamp technique” ?
the cytoplasmic side of the channel is facign into the bath solution.
** makes it very easy to change the internal concentration of a ligand
What is “The outside out-out excised patch clamp technique” ?
the extracellular side of the channel is facing out into the bath.
** makes it very easy to change the concentrations of an external ligand.
The period of time during an action potential when “a second response is not possible regardless of strength or duration of stimulus” is called …?
Absolute Refractory Period
The period of time during an action potential when “a second response can be elicited but at a greater “cost” (strength/duration) is called…?
Relative Refractory Period
The diameter of a Giant squid axon is around ____ micrometers
Where as the mammalian axon is around 2 micrometers.
800 nanometers
The amplitude of an action potential depends on the external ____ concentration.
a. K+
b. Na+
c. Cl-
d. Ca2+
answer: B Na+
Resting membrane potential (Vm) is changed ______ (little or alot) by Na+ concentrations.
Vm is changed very little by Na+
Resting membrane potential (Vm) is changed ______ (little or alot) by K+ concentrations.
Vm depends strongly on the K+
- In a Current-Voltage relationship graph, the early current is a potential difference created by which ion?
- how does it behave as the membrane potential becomes more positive?
Na+
Sodium current reverses to outflow and positive current at its reversal potential (around +50 mV)
- In a Current-Voltage relationship graph, the late current is a potential difference created by which ion?
- how does it behave as the membrane potential becomes more positive?
K+
K+ curve continues to increase as the driving force gets larger
What ion blocker(s) are used to inhibit early current?
TTX - tetrodotoxin
STX - Saxitoxin
What ion blocker(s) are used to inhibit late current?
TEA - tetraethylammonium
Which ion Blocker (used in early and late currents) resides in pufferfish and is 1,200x more poisonous than cyanide?
TTX tetrodotoxin
When channels are assumed to always be fully open the current through them is linear or “ohmic”
T or F?
True
Conductance changes with voltage when channels are assumed to always be fully open.
T or F?
False
Conductance does not change with voltage when channels are assumed to always be open.
The opening of Na and K channels depends on resistance and conductance.
T or F?
False
depends on Voltage!
