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PHPY 301 > Lec 10 & 11 > Flashcards

Lec 10 & 11 Flashcards

1
Q

One of the 3 roles of K+ channels is to make the membrane potential (Vm) more _____ (positive/negative)

A

negative

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2
Q

One of the 3 roles of K+ channels (during repolarization) is to resist depolarization of the cell towards action potential threshold.

T or F?

A

True

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3
Q

One of the 3 roles of K+ channels is to speed up the rate of firing of action potentials. (encourage burst firing)

T or F?

A

False;

to slow the rate of firing of action potentials

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4
Q

What are the electrophysiological 4 major types of currents?

A
  1. delayed outward rectifiers
  2. transient outward rectifiers (A-type currents)
  3. Ca2+-activated K+ currents
  4. inward rectifiers
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5
Q

What is does “delayed” mean?

A

delay in activation

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6
Q

What does “Rectifier” mean?

A

current that flows better in one direction than another.

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7
Q

Which electrophysiological current types are voltage-gated K+ currents?

A

delayed outward rectifiers

and

transient outward rectifiers

(both are outward rectifiers)

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8
Q

Identification of the first gene for a voltage-gated K+ channel occurred through genetic analysis of what organism?

A

Shaker fruit fly.

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9
Q

The “Shaker” mutation was found in a gene coding for a voltage-gated K+ channel. This led to the discovery of a family of K+ channels called the _____ Family.

A

Shaker Family

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10
Q

The Shaker family is non-voltage gated.

T or F?

A

False

they are all voltage gated and delayed rectifiers

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11
Q

Members of the Shaker Family can display a range of inacivation properties.

T or F?

A

True

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12
Q

A-Type K+ Channels are not voltage gated.

T or F?

A

False: they are.

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13
Q

A-Type K+ channels refers to currents that are ___ (high/low) threshold. They _____ (slowly/rapidly) activate and inactivate K+ current.

A

low

rapidly

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14
Q

A-type K+ channels (like Na+ channels) are partially _______ (activated, inactivated) at the resting membrane potential (Vm).

A

inactivated

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15
Q

Like __-Type Ca2+ channels, A-Type K+ Channels activate at potentials below threshold and can regulate the rate at which a cell reaches the threshold for an action potential.

A

T type

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16
Q

A large A-Type current will ______ (increase/decrease) the interspike interval.

A

increase

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17
Q

A small A-Type current will ______ (increase/decrease) the interspike interval.

A

decrease

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18
Q

Kv-Type channel’s inactivation can depend on a sequence in the a-subunits or B subunits:

what is the a-subunit inactivating structure?

what is the B-subunit inactivating structure?

A

N - terminal domain ball

and

B-subunits,itself, blocks the channel.

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19
Q

In different Kv-type K+ channels, B-subunits can alter the inactivation rates.

T or F?

A

True

Some B-subunits attached to a Kv-Type channel will inactivate and some wont.

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20
Q

The KCNQ (or Kv7) family were originally identified because these genes are mutated in a condition known as…

*also found in neurons*

A

long QT syndrome

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21
Q

The neuronal version of KCNQ (Kv7) were discovered through sensitivity to muscarinic activation and were named __-type K+currents/channels.

A

M-type

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22
Q

Defects in M-type K+ channels in main neuronal members of the KCNQ (Kv7) Family underlie a type of familial ______ ______. (disease)

A

neonatal epilepsy

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23
Q

The Kv7 family mediate currents that are ____ (low/high) threshold, ______ (inactivating, non-inactivating), and very ____ (fast/slow).

A

low threshold

non-inactivating

very slow

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24
Q

A member fo the Kv7 family can contribute to the _______ (depolarization/repolarization) of the cardiac action potential because the action potential in cardiac muscle is also very ____ (slow/fast).

A

repolarization

slow

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25
Q

Activation of M-type K+ channels tends to _____ (inhibit/activate) firing over a long time scale.

A

inhibit

26
Q

The loss of M-type currents tends to neuronal ________ (hypoexcitabiility/hyperexcitability).

A

hyperexcitability

without M-type there would be repetitive firing.

27
Q

The two main families of Ca2+ activated K+ channels are:

A

large conductance (BK) channels

and

small conductance (SK) channels

28
Q

Large conductance (BK) K+ channels are sensitive to what stimulus?

A

voltage

and

Ca2+

29
Q

Small conductance (SK) channels are sensitive to what stimulus?

A

only to Ca2+

30
Q

SK K+ channels increase their open probability (Po) in response to membrane depolarization.

T or F?

A

False

BK channels increase Po in response to depolarization.

31
Q

What is defined as “the accumulation of Ca2+ in a cell during the firing of multiple action potentials can lead to a progressively larger Ca2+ activated K+ current, which can turn off cell firing and causing this event” ?

A

spike frequency adaptation

32
Q

What is the name of the current that accumulates as a result of spike frequency adaptation (SFA) ?

A

slow afterhyperpolarization sAHP

33
Q

What substance blocks Ca2+ entry and blocks sAHP slow afterhyperpolarization ?

A

Cd2+ cadmium ions

34
Q

An increase in Ca2+ levels can cause Ca2+ activated K+ channels to burst fire.

T or F?

A

True

35
Q

BK large conductance Ca2+ activated K+ channels have 6 transmembrane proteins.

T or F?

A

False;

7

36
Q

Inwardly rectifying K+ channels have only 2 transmembrane spanning regions and therefore must possess the voltage-sensing S4 region.

T or F?

A

False;

Inwardly rectifying K+ channels have only 2 transmembrane spanning regions and therefore DO NOT possess the voltage-sensing S4 region.

37
Q

Measurements of current through single Kir (inwardly rectifying) channels show that there is more likely to be current at ________ (negative/positive) voltages.

A

negative!

38
Q

What family or type of K+ channel requires the presence of Mg2+?

A

Kir or inward rectifying K+ channels

39
Q

Kir-type K+ channels have a voltage dependent block .

T or F?

A

True

Mg2+ does it.

40
Q

In Kir-type channels , the current is greater on which side of the cell?

inside or outside?

A

inside

  • due to Mg2+ on the inside , there is no current on the outside
41
Q

In Kir channels, Mg2+ occludes the channel pore and prevents the exit of K+. This prevents the entrance and exit of K+ ions temporarily.

T or F?

A

False;

K+ ions can still enter the cell by displacing Mg2+

42
Q

Inwardly rectifying K+ channels do not carry outward current.

T or F?

A

False;

Outward current tends to maintain a low membrane potential acting like leak channels

43
Q

By increasing or decreasing the activity of the Kir channel currents, they can therefore change the membrane potential to make the cell more or less likely to fire action potentials.

What type of channel is an example of this?

A

ATP - sensitive (KATP ) channel

44
Q

An example of a Kir channel that can be modulated is…

A

ATP-sensitive channel (KATP)

45
Q

KATP -type Inward rectifying channels are closed by ______ (increases/decreases) in the ATP/ADP ratio which regulates insulin release in a glucose-dependent manner.

A

increases

therefore by increasing the amount of ATP in the cell, you will close the channels.

46
Q

What type of K+ channel is glucose dependent?

A

KATP inwardly rectifying

47
Q

What drug is used to enhance insulin release by blocking KATP channels through an action on a SUR receptor?

A

Sulfonlyureas

48
Q

What class of drug is used in the treatment of type II diabetes?

A

Sulfonlyureas

49
Q

What type of Ca2+ channels are important in the delivering of Ca2+ to the cell and causing the release of insulin to the body?

A

N and P|Q type channels

50
Q

Inwardly Rectifying K+ Channels:

are selective for K+ and therefore tend to __________(depolarize, hyperpolarize) the cell and make it less likely to fire an action potential.

A

hyperpolarize

51
Q

Inwardly Rectifying K+ Channels:

are gated

T or F?

A

False not gated

52
Q

Inwardly Rectifying K+ Channels:

Cell voltage is never below Ek, and these channels function to allow flow of K+ ions out of the cell. much like a leak channel.

T or F?

A

True

53
Q

Inwardly Rectifying K+ Channels:

Since they are not gated, they contribute to rapidly raising the resting membrane potential.

T or F?

A

False;

contribute to setting the resting membrane potential.

54
Q

What are 2 examples of modulated Inward rectifying K+ channels?

A

GIRK channels

KATP channels

55
Q

GIRK and KATP channels cause cahgnes in resting membrane potential and therefore change the excitability of the cell.

T or F?

A

True

exciteability = liklihood of firing action potentials.

56
Q

Sulfonylurea drugs are used in maintaining blood pressure and act by blocking KATP channels, which increases the excitability of the Beta cells, leading to an increase in insultin release.

T or F?

A

False

used in treatment of type 2 diabetes

57
Q

What family is comprised of a tandem pore or two pore K+ channel (K2P) ?

A

TWIK family

58
Q

Which family includes tandem pores and mediates “leak” K+ currents in many types of cells?

A

TWIK family

59
Q

Are the TWIK family of K+ channels gated?

A

no

60
Q

A mutation in one type of two pore K+ channel (TRESK) has been linked to a familial type of ________.

A

migraine headache.

61
Q
A

PHPY 301 (23 decks)

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