SAKMANN AND NEHER INVENT PATCH-CLAMPING Flashcards Preview

Neuroscience > SAKMANN AND NEHER INVENT PATCH-CLAMPING > Flashcards

Flashcards in SAKMANN AND NEHER INVENT PATCH-CLAMPING Deck (98)
Loading flashcards...
1

A method to measure the behavior of a single ion channel

SAKMANN AND NEHER
PATCH-CLAMPING

2

Erwin Neher and Bert Sakmann invented a new technique called patch
clamping, which allowed them to study the

behavior of a single ion channel

3

1991 Nobel Prize in Medicine or Physiology

Neher and
Sakmann

4

The ion channel is
inserted in the

membrane that is
in the lumen of the electrode,

5

However, whether
open for a longer or shorter period, the conductance of the Na channel (the amount of current passed
during any instant in time) is always the same. T/F

True

6

individual channel opens and closes

very rapidly

7

channels have ___ conductances

unitary

8

If the same depolarizing pulse was presented a
second time, or a third or fourth time, the same inward current pattern was evoked. This pattern
of current flowing through the entire axon is called the

macroscopic current

9

patterns of inward current evoked in a single Na channel, called the

microscopic current,

10

The opening and closing of an individual channel was variable because the behavior of any
channel is

probabilistic.

11

What the membrane potential does is to change the ___that a
channel will open.

probability

12

In the case of the Na channel, depolarization increases the probability that the

activation gate will open.

13

hyperpolarization
increases the probability of

closing the Na activation gate

14

depolarization increases the probability that the inactivation gate will

close

15

hyperpolarization
increases the probability that the inactivation gate will

open

16

How then do we reconcile the stereotyped current response of the squid giant axon to a
depolarization of -10 mV, the shape of the macroscopic current, with the highly variable
response of an individual Na channel, the microscopic current, to exactly the same
depolarization?

squid giant
axon during voltage clamp shows the summated (or averaged) currents through many ion
channels in the entire membrane of the axon rather than the current through a single channel.

17

was simple to calculate
the probability of a Na channel opening as a function of

membrane potential

18

function of membrane potential. That function is
shown in Fig. 4E, and has a ___shape

sigmoidal

19

inward currents are
shown as

downward deflections

20

Current through a single
channel is called the

microscopic
current

21

The sum of many such
microscopic currents shows that most
channels open in the initial___after
which the probability of channel
openings diminishes because of channel
inactivation.

1-2 ms,

22

The macroscopic
current resulting from the current
flowing through all of the Na channels
while

voltage clamping the entire axon

23

is very similar
to the summed microscopic current in C.

macroscopic current

24

The probability of Na channel
opening depends on the

membrane
potential,

25

Notice that the
probability is virtually zero (few or no
channels open) at

-60 to -80 mV

26

probability of channel opening is about
80% even when the membrane is
depolarized to

+40 mV

27

Depolarizing steps cause outward currents which are seen as

(upward
deflections

28

Notice that the K channel opens with different
latencies to the depolarization and that the channels
stay open for the length of the

depolarization,

29

the probability-membrane
potential function is similar to both the K
conductance-membrane potential function and to the
Na conductance-membrane potential function

T/F

T

30

Strong hyperpolarization virtually ensures that
52
activation gates are closed, since the probability of a Na or K channel being open at ____
is just about zero (

-70-80 mV