Ion channels Flashcards Preview

PM2C Autumn Amy L > Ion channels > Flashcards

Flashcards in Ion channels Deck (23):
1

Why are ion channels needed?

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

2

How do ion channels work?

They are selective
Ions pass down their electrochemical gradients through the channels

3

List 5 types of ion channel

Potassium channels
Sodium channels
Calcium channels
TRP channels
Ligand-gated channels

4

How do potassium channels regulate cell excitability?

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

5

Describe the structure of potassium channels

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)

6

Give an example of how a potassium channel works

Minoxidil open potassium channels
Causes hyperpolarisation
= muscle relaxation = vasodilation

7

Where are sodium channels found?

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

8

Describe the structure of sodium channels

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

9

Where are calcium channels found?

In the membranes of the most excitable cells
Voltage-gated

10

Describe the structure of the calcium channel

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

11

What are TRP channels?

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

12

What can ligand-gated channels also be known as?

Ionotropic receptors

13

What is the role of ligand-gated channels?

They link ligand binding to an ionic flux
Fast synaptic transmission

14

Describe the structure of ligand-gated channels

Sub-units combine to form pentamers (or tetramers)
Families are diverse`(different combinations of sub-units)

15

How do acetyl choline receptors work?

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

16

What type of receptor is the acetyl choline receptor?

Ligand-gated receptor

17

Describe the structure of the acetyl choline receptor

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

What is succinylcholine?

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

What is the indication of succinylcholine?

For surgery - neuromuscular blockade (short duration)

20

What is granisetron?

5-HT3 agonist
5-HT mediates synaptic transmission to medullary vomiting centre and area postrema

21

What is the indication of granisetron?

For nausea and vomiting caused by chemo/radiotherapy

22

What is diazepam?

Full agonist of the GABA(A) receptor
Enhance the activity of the GABA receptor

23

What is the indication of diazepam?

Anxiety or insomnia