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NPB100 > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

Changes in membrane potential
are due to

A

movement of ions
across the cell membrane

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2
Q

Movement of ions is most often
controlled by the opening and
closing of

A

ion channels

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3
Q

What do patch clamps measure?

A

Ion flow - current

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4
Q

What are the 3 types of patch recordings? Explain the difference

A

Whole cell - strong pulse of suction of the pipette. The cytoplasm is continuous with the pipette interior

Inside-out - expose the intracellular cell to air and cytoplasmic domain is accessible.

Outside-out - retract the pipette, ends of the membrane anneal and extracellular domain is accessible

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5
Q

Voltage-clamp measures

A

voltage

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6
Q

Current-clamp measures

A

voltage

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7
Q

Identify examples of when it would be appropriate to use inside-out vs. outside-out patch recordings

A

Inside-out patch recording: to observe ion channel function after exposing the membrane to intracellular metabolites

Outside-out: to observe ion channel function after exposing the membrane to extracellular ligands

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8
Q

Channels switch between open and closed states almost

A

instantaneously

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9
Q

inward current is (+) or (-)?

A

negative

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10
Q

outward current is (+) or (-)?

A

positive

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11
Q

T/F At rest, single ion channel open time varies, and fluctuates around a mean
open time characteristic of that channel type.

A

T

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12
Q

What do synaptic or sensory inputs to the neuron change?

-the probability that
the channel will open
-the mean open time
-both
-neither

A

the probability that
the channel will open

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13
Q

What determines the magnitude of current
flow through an open ion channel?

A

-single channel conductance of the ion channel (pore
dimensions, charges on channel wall, etc
-Forces causing the ions to move
– Electrical driving force (charge difference)
– Chemical driving force (concentration gradient)

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14
Q

What determines Eion?

A

Electrical driving force and chemical driving force

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15
Q

What formula calculates the driving force of a current?

A

Vm-Eion

The difference between the membrane potential and the equilibrium potential of that ion.

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16
Q

What is the current if the membrane potential is at -90 and the Eion is -90?

A

0 because

I=G(Vm - Eion)
I=G(-90 - -90) = 0

17
Q

When a positive ion leaves the cell, the current is ?

A

positive outward

18
Q

An IV curve measures ?

A

current through a single channel, plot current as a function of voltage

19
Q

What does an IV curve do?

A

Clamping the voltage to different values to see the flow of current as a result.

20
Q

What does an IV curve tell you?

A

How the current that flows through that channel changes as you change the membrane potential.

21
Q

What does a linear/non-rectifying/ohmic IV curve tell you about the conductance?

A

Conductance is constant throughout all voltage. Flow of current is linear with respect with voltage

22
Q

How do you find the Eion of a IV curve?

A

Equilibrium potential is the patch potential when there is no channel current. X=0, look at your y intercept.

23
Q

How do you find the reversal potential on an IV curve?

A

X intercept - when current aka I is equal to 0. The membrane potential at which the sign of the current changes.

24
Q

How would you be able to tell if a channel is permeable to a single ion looking at a IV curve?

A

Reversal potential is equal to the equilibrium potential of that ion. So if the reversal potential is -70mV, it is permeable to K+ ions because Ek+ is -70mV.

25
Q

Reversal potential is a property of?
Equilibrium potential?
Membrane potential?

A

channel
ion
cell

26
Q

If the membrane potential is equal to the reversal potential, the driving force is

A

0

27
Q

What are the 2 types of ion channels?

A

a) channels activated by physical changes in the cell membrane
b) channels activated by ligands

28
Q

There are 2 types of channels that are activated by physical changes in the cell membrane. What are they?

A

voltage-activated and stretch-activated

29
Q

There are 2 types of channels activated by ligands. What are they?

A

Extracellular activation and intracellular activation

30
Q

What is the difference between direct and indirect transmitter action?

A

Direct - transmitter binds to the ionotropic receptor and the channel opens. Speed is 1 to 1

Indirect - transmitter binds to the metabotropic receptor which sends an intracellular second messenger to the ion channel, allowing it to open. Amplification

31
Q

Voltage-gated ion channels are activated by?

A

change in membrane potential

32
Q

slide 48

A

NPB100 (8 decks)

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