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Therapeutics > W6 - Ion channels > Flashcards

W6 - Ion channels Flashcards

1
Q

How many genes encode K channels

A

70

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2
Q

what are the purpose of the K channels in the body

A

frequency and shape of action potentials

Secretion of hormones

Secretion of neurotransmitters

Membrane potential

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3
Q

What is the standard amount of K+ in a cell

A

150 mMOL

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4
Q

What is the extracellular amount of K+ at rest

A

2.5 mMOL

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5
Q

At rest what happens in response to the concentration gradient K+

A

due to electrochemical gradient K+ moves out of the cell into the extracellular fluid

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6
Q

What about Na+ and Ca2+ (electrochemical gradient

A

They have the opposite to K+ so move into the cell down the concentration gradient from the extra cellular fluid.

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7
Q

Describe the structure of K+ channel

A

There is a N (NH2) terminus and C (COOH) terminus located intracellularly

There are 6 subunits S1 - S6 which are connected across the membrane (transmembrane)

There is a gap between S5 and S6 which is where the K+ ion is conducted through the membrane

S4 has a positive charge so is believed to be sensitive to voltage.

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8
Q

What is an example of something that opens K+

A

Minoxidil opens the K+ channel and causes hyper polarization in smooth muscle cells, muscle relaxation and hence vasodilation.

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9
Q

What can minoxidil be used to treat

A

can be used to treat hypertension in combination with a diuretic and beta adrenoreceptor blocker

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10
Q

What type of channel is a sodium ion channel

A

voltage gated

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11
Q

How many alpha subunits makes up a sodium channel

A

one pore forming alpha subunit (which can be associated with either one or two beta subunits)

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12
Q

How many alpha subunits is a Potassium channel made up of

A

4 pore forming alpha subunits

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13
Q

what is the minimum amount of genes coding a sodium channel

A

at least 10

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14
Q

Describe the structure of a sodium channel

A

There is an amino terminus and a carboxyl terminus intracellularly

There are 6 Segments denoted s1 through to s6

S4 again is the voltage sensing subunit being positively charged

there is a gap between segment 5 and 6

While the transmembrane subunits they are connected to form the alphas subunit

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15
Q

What are the two terminus’s of the sodium channel

A

carboxyl and amino terminus

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16
Q

how many segments are there

A

6

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17
Q

what is the voltage sensing segment

A

4

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18
Q

why is s4 believed to be the voltage sensing segment

A

due to its positive charge

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19
Q

where do the ions move through

A

there is a gap between s5 and s6

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20
Q

What is an example of a drug that affect the sodium ion channel

A

lidocaine

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21
Q

what does lidocaine do

A

blocks voltage gated sodium channels

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22
Q

what is the primary target of lidocaine

A

Nav1.5 which is the main cardiac sodium channel

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23
Q

what is the indication of lidocaine

A

ventricular arrhythmias, especially after myocardial infarction in addition to local anaesthesia

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24
Q

what is myocardial infarction

A

heart attack

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25
Q

What type of channel is Ca2+

A

voltage gated ion channel

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26
Q

what do Ca2+ channels form

A

hetero oligomeric complexes

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27
Q

What is an oligomer

A

a polymer whose molecules consist of relatively few repeating units.

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28
Q

What is a hetero oligomer

A

Functional protein complexes formed by oligomerization of similar subunits.

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29
Q

Describe the Ca2+ hetero oligomeric complex

A

The α1 subunit is pore-forming and provides the extracellular binding site(s) for practically all agonists and antagonists.

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30
Q

What are the three families of Ca2+ channels

A

high voltage activated dihydropyridine sensitive channels

The high voltage activated dihydropyridine insensitive channels

low voltage activated channels

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31
Q

What does L type refer to

A

high voltage activated dihydropyridine sensitive channels

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32
Q

What does CaV1.x refer to

A

high voltage activated dihydropyridine sensitive channels

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33
Q

What does CaV2.x refer to

A

The high voltage activated dihydropyridine insensitive channels

34
Q

What does T type refer to

A

low voltage activated channels

35
Q

What does CaV3.x refer to

A

low voltage activated channels

36
Q

what does alpha 2 delta 1 and 2 do

A

bind gabapentin and pregabalin

37
Q

Describe the structure of a high voltage activated calcium channel

A

N terminus C terminus intracellularly similar to K+ and Na+

Contains a gamma and a beta subunit (low voltage activated does not have either of these)

Contains alpha 2 delta subunit

Contains 4 domains which consist of 6 transmembrane sections

as per the K+ and Na+ S4 is the voltage sensitive section

there is a gap between s5 and s6 which Ca2+ travels through

38
Q

What two terminals does a Ca2+ channel have

A

NH2

CooH

39
Q

What are the different subunits contained in a calcium channel

A

Alpha subunit
Beta subunit
Gamma Subunit

40
Q

How many sections does a domain of an alpha subunit have

A

6

41
Q

what is the voltage sensitive section of a domain of an alpha subunit

A

4

42
Q

where does the ca2+ travel through

A

there is a gap between s5 and s6

43
Q

what is a drug which effects the ca2+ channe

A

verapamil

44
Q

what does verapamil do

A

blocks voltage gated Ca”+ channels (L type)

45
Q

What effect does verapamil have

A

blocks calcium influx in myocardial and vascular smooth muscle cells.

Lead to a reduction in cardiac and VSm contraction

bringing about a dilation in coronary and systemic arteries

46
Q

what is the indication of verapamil

A

supraventricular arrhythmias, angina, hypertension (dose and preparation dependent)

47
Q

What channels effect epilepsy

A

K+
Ca2+
Na+

48
Q

What channels effect diabetes

A

K+

Katp

49
Q

What channels effect ataxia

A

K+

Ca2+

50
Q

what is ataxia

A

People with ataxia lose muscle control in their arms and legs. This may lead to a lack of balance, coordination, and trouble walking. Ataxia may affect the fingers, hands, arms, legs, body, speech, and even eye movements.

51
Q

What channels affect pain

A

Na+

Ca2+

52
Q

What are ligand gated channels often known as

A

ionotropic receptors

53
Q

what do ligand gated channels do

A

they link ligand binding to an ionic flux

54
Q

How many subunits are ligand gated ion channels made up of

A

4-5

55
Q

How many ACh receptors are there

A

2

56
Q

What are the 6 receptor classes

A 
nAChR
Glutamate (ionotropic)
5HT3
Glycine
GABAa
ATP receptors (P2X)
57
Q

What gated Ion is nAChR

A

Na+

58
Q

What effect does Na+ have on the nAChR receptor

A

Excitatory

59
Q

What gated ion channel is Glutamate

A

Na+

60
Q

What effect does Na+ have on the Glutamate receptor

A

Excitatory

61
Q

What gated ion channel is 5HT3

A

Na+

62
Q

What effect does Na+ have on 5HT3

A

Excitatory

63
Q

What gated ion channel is Glycine

A

Cl-

64
Q

What effect does Cl - have on Glycine

A

inhibitory

65
Q

what gated ion channel is GABAa

A

Cl-

66
Q

what effect does Cl- have on GABAa

A

inhibitory

67
Q

What type of ion channels is P2X

A

Na+
K+
Ca2+
Exceptionally CL

68
Q

What are ligand gated ion channels

A

integral membrane proteins that contain a pore which allows the regulated flow of selected ions across the plasma membrane

69
Q

what type of process is ion flux

A

passive

70
Q

what is ion flux driven by

A

electrochemical gradient

71
Q

what are the channels opened by

A

ligand binding that triggers a conformational change that results in the conducting state

72
Q

What is the abbreviation of ligand gated ion channel

A

LGIC

73
Q

What scale do LGIC’s mediate fast synaptic transmission

A

millisecond time scale

74
Q

Where do LGIC’s mediate fast synaptic transmission

A

nervous system and somatic neuromuscular junction

75
Q

what suggests that LGIC’s have additional functions

A

expression by non excitable cells

76
Q

Describe the structure of a typical ligand gated channel

A

There is a Nh2 terminus and a cooh terminus extra cellularly

ACH binding site extracellularly near the Nh2 terminus

there are 5 repeating subunits

in each subunit there is TM2 which is the voltage sensitive

77
Q

What are exceptions to the standard structure

A

Ach, Gaba and Glycine receptor channels

Glutamate receptor channels

ATP receptor channels

78
Q

What drug can affect nAChR

A

Succinylcholine

79
Q

What does it do

A

its a full agonist of the nAChR receptor activates the channel

80
Q

what effect does Succinylcholine have

A

mimics the effects of ACh but is not subject to breakdown by AChE

81
Q

Indication of Succinylcholine

A

Neuromuscular blocade for surgery

Therapeutics (50 decks)

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