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Neuroscience Unit 3 > Lecture 6: Channels and Transporters > Flashcards

Lecture 6: Channels and Transporters Flashcards

1
Q

When the membrane potential is +52mV, what change in current occurs?

A

early inward Na+ current is missing

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2
Q

When the membrane potential is +65mV, what change in current occurs?

A

early inward Na+ current reverses to an outward flow

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3
Q

What technique provided the first direct evidence for single channels? Describe it

A
  • Patch clamp technique
  • voltage change activates channel openings
  • glass pipet is sealed against cell membrane
  • all current flows through electrode
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4
Q

In the patch-clamp technique, what do macroscopic and microscopic currents result from?

A
  • Macroscopic - current flow through many channels

- Microscopic - current flow through a single channel

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5
Q

Ion channels open in a stochastic (___) manner

A

random

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6
Q

Depolarizing stimulus _____ the probability that the Na+ channel is opened when a K+ channel is experimentally blocked

A

increases

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7
Q

The sum of many _____ trials approximates the _____ of the _____ currents from the whole cell

A
  • microscopic
  • time course
  • macroscopic
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8
Q

Which channels specifically inactivate? Which just close?

A
  • Na+ inactivate

- K+ close

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9
Q

What forms the binding sites in the K+ channels? Whtt energetic role do they play?

A
  • O atoms of 5 AA lining channel

- stabilize the energetically unfavorable shedding of H2O

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10
Q

Which atom, Na+ or K+ is larger? Which is effectively larger? Why? Which ion channel therefore has a smaller pore?

A
  • K+ is larger
  • Na+ is effectively larger - more water molecules which are more tightly bound
  • K+ channel has smaller pore
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11
Q

How many types of Na+ channels exist?

A

One

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12
Q

How many types of K+ channels exist?

A

Multiple

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13
Q

What three characteristics differentiate K+ channels?

A
  1. low vs high voltage activation
  2. rate of activation (how quickly max conductance is reached)
  3. inactivation properties (fast, slow, do/don’t inactivate)
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14
Q

Describe activation of fast After Hyperpolarization. Which channel is involved?

A
  • BK K+ channel
  • activated by Ca2+ and depolarization; then rapid inactivation
  • shortens AP by quickly repolarizing membrane
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15
Q

Describe activation of medium After Hyperpolarization. Which channel is involved?

A
  • IK and SK K+ channels
  • no inactivation
  • slowly activated by Ca2+ entry; early interspike interval
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16
Q

Describe slow After Hyperpolarization

A

limits firing by an unknown channel

17
Q

Ka is the A-type _____ potassium channel. It inactivates _____.

A
  • voltage-sensitive

- rapidly

18
Q

Kdr is the _____ potassium channel. It is ______ and inactivates _____ or _____.

A
  • delayed rectifier
  • voltage sensitive
  • slowly
  • does not inactivate
19
Q

Kbk is the _____ (name), ___-activated, _____ potassium channel. It requires both _____ and _____ to be activated.

A
  • big conductance
  • Ca2+
  • voltage-sensitive
  • Ca2+ and depolarization
20
Q

What are the 5 channel timings of APs?

A
  1. Na+ channels open
  2. Na+ channels inactivate; Ka and Kdr channels open
  3. Kbk channels open
  4. Ca2+ channels open
  5. other known and unknown K+ channels open
21
Q

Which type of channel usually only allows one type of ion to pass through? Which usually allows multiple?

A
  • Voltage-gated = 1

- Ligand-gated = multiple

22
Q

Which K+ channel plays a + role in tumorigenic human mammary cells?

A

Kv1.4

23
Q

So many genes encoding K+ channels allow them to differ in which three aspects?

A

Activation
Gating
Inactivation

24
Q

Congenital stationary night blindness, familial hemiplegic migrane, and episodic ataxia type two are all due to mutations in ______ channels.

A

Voltage-gated Ca2+

25
Q

Generalized epilepsy with febrile seizures is caused by a _____ channel defect

A

Na+

26
Q

Benign familial neonatal convulsion is caused by a _____ channel mutation

A

K+

27
Q

Teradotoxin (puffer fish), saxitoxin (red tide), Alpha- and beta-toxins (scorpion), and batrachotoxin (frogs) all affect ___ channels.

A

Na+

28
Q

Dendrotoxin (wasps) and apamin (bees) affect ___ channels

A

K+

29
Q

w-conotoxins and w-agatoxin affect ____ channels

A

Ca2+

30
Q

Active ion transporters are _____ which create and maintain ion gradients using ____ as the energy source.

A
  • membrane proteins

- ATP

31
Q

Ion exchangers use the _____ as an energy source to exchange ions.

A

electrochemical gradients of co-transported ions

32
Q

What is co-transport of ions?

A

2 or more ions/molecules move in the same direction across the membrane

Neuroscience Unit 3 (8 decks)

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