Ion channels Flashcards

1
Q

Why are ion channels needed?

A

Ions are rebounded off the cell because of theirs and the membrane’s charge

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2
Q

How do ion channels work?

A

They are selective

Ions pass down their electrochemical gradients through the channels

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3
Q

List 5 types of ion channel

A
Potassium channels
Sodium channels
Calcium channels
TRP channels
Ligand-gated channels
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4
Q

How do potassium channels regulate cell excitability?

A

Through:
Frequency and shape of action potentials
Secretion of hormones and neurotransmitters
Membrane potential

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5
Q

Describe the structure of potassium channels

A

C terminus us larger (phosphorylation events can change the properties of the channel)
6 transmembrane domains
S4 has a positive charge = voltage centre = channel is voltage-gated
Can get different combinations of α sub-units (homomeric or heteromeric)

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6
Q

Give an example of how a potassium channel works

A

Minoxidil open potassium channels
Causes hyperpolarisation
= muscle relaxation = vasodilation

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7
Q

Where are sodium channels found?

A

Sodium channels are present in the membranes of the most excitable cells
Voltage-gated

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8
Q

Describe the structure of sodium channels

A

1 pore-forming α sub-unit , which may be associated with either 1 or 2 of the β sub-units
6 transmembrane domains

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9
Q

Where are calcium channels found?

A

In the membranes of the most excitable cells

Voltage-gated

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10
Q

Describe the structure of the calcium channel

A

Calcium channels form hetero-oligomeric complexes

The α sub-unit is pore-forming and provides the extra-cellular binding sites for practically all agonists/antagonists

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11
Q

What are TRP channels?

A

Transient receptor potential channels
Some are sensory (e.g. heat, pain)
Multiple ions can pass through the channels

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12
Q

What can ligand-gated channels also be known as?

A

Ionotropic receptors

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13
Q

What is the role of ligand-gated channels?

A

They link ligand binding to an ionic flux

Fast synaptic transmission

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14
Q

Describe the structure of ligand-gated channels

A

Sub-units combine to form pentamers (or tetramers)

Families are diverse`(different combinations of sub-units)

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15
Q

How do acetyl choline receptors work?

A

Sodium flows along its concentration gradient and causes depolarisation of cell
MUscle contraction
Increased probability of neurone firing action potential

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16
Q

What type of receptor is the acetyl choline receptor?

A

Ligand-gated receptor

17
Q

Describe the structure of the acetyl choline receptor

A

4 or 5 sub-units
Each sub-unit has 4 transmembrane domains
TM2 from each sub-unit lines the ion channel pore
Different nAChRs exist - depending on which sub-units are assembled into the complex

18
Q

What is succinylcholine?

A

Full agonist of the nACh receptor
Mimics the effects of ACh but is not subject to breakdown ACh-ase
So sits in receptor longer so it can’t respond to other signals

19
Q

What is the indication of succinylcholine?

A

For surgery - neuromuscular blockade (short duration)

20
Q

What is granisetron?

A

5-HT3 agonist

5-HT mediates synaptic transmission to medullary vomiting centre and area postrema

21
Q

What is the indication of granisetron?

A

For nausea and vomiting caused by chemo/radiotherapy

22
Q

What is diazepam?

A

Full agonist of the GABA(A) receptor

Enhance the activity of the GABA receptor

23
Q

What is the indication of diazepam?

A

Anxiety or insomnia