Flashcards in Ion channels Deck (23):
Why are ion channels needed?
Ions are rebounded off the cell because of theirs and the membrane's charge
How do ion channels work?
They are selective
Ions pass down their electrochemical gradients through the channels
List 5 types of ion channel
How do potassium channels regulate cell excitability?
Frequency and shape of action potentials
Secretion of hormones and neurotransmitters
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)
Give an example of how a potassium channel works
Minoxidil open potassium channels
= muscle relaxation = vasodilation
Where are sodium channels found?
Sodium channels are present in the membranes of the most excitable cells
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
Where are calcium channels found?
In the membranes of the most excitable cells
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
What are TRP channels?
Transient receptor potential channels
Some are sensory (e.g. heat, pain)
Multiple ions can pass through the channels
What can ligand-gated channels also be known as?
What is the role of ligand-gated channels?
They link ligand binding to an ionic flux
Fast synaptic transmission
Describe the structure of ligand-gated channels
Sub-units combine to form pentamers (or tetramers)
Families are diverse`(different combinations of sub-units)
How do acetyl choline receptors work?
Sodium flows along its concentration gradient and causes depolarisation of cell
Increased probability of neurone firing action potential
What type of receptor is the acetyl choline receptor?
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
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
What is the indication of succinylcholine?
For surgery - neuromuscular blockade (short duration)
What is granisetron?
5-HT mediates synaptic transmission to medullary vomiting centre and area postrema
What is the indication of granisetron?
For nausea and vomiting caused by chemo/radiotherapy
What is diazepam?
Full agonist of the GABA(A) receptor
Enhance the activity of the GABA receptor