Communication By Receptors Flashcards
What can receptors be connected to?
Ion channels (ionotrophic receptors) G proteins (G protein coupled receptors or coupled ion channels)
What do receptors do?
Help neurotransmitters to communicate with the post synaptic cell
What receptors link to ion channels
Ionotrophic receptors
What receptors link to G proteins
Metabotrophic receptors
What are ionotrophic receptors also known as?
Ligand gated ion channels
What does ligand mean?
Neurotransmitter or agonist
What are the subunits that ion gated receptors are composed of?
Combination of 5 Alpha, beta, delta or gamma
How many regions does each subunit have that span the membrane?
4
What are the subunits comprised of across the membrane?
Polypeptides which are made up of amino acids
What is a binding site?
A part of the chemical which is exposed to allow neurotransmitters to attach to the receptor to open the ion channel
What happens when a ligand binds?
The molecules change confirmation and let the ions come into the cell
How is an action potential stimulated
Different neurotransmitters and ions channels specify different ions into the cell. If you increase positive ions in the cell it will make the cell fire
What are the neurotransmitters that allow sodium and calcium into the cell
Acetylcholine and glutamate
What are the neurotransmitters that let negative ions into the cell
GABA and glycine
What effect does letting negative ions into the cell have on action potentials
It inhibits them
What is a metabotrophic receptor made of
A single polypeptide.
It does not have subunits.
It has 7 membrane spanning domains which are alpha helix coil
How does a metabotrophic receptor bind to the transmitter
The neurotransmitter binds to the alpha helices. It then causes the receptor to bind to the G protein
What is the G protein made up of
Alpha, beta and gamma and GDP- a low energy protein which is bound to alpha.
What happens when the neurotransmitter binds?
It causes phosphorylation to the GDP to make it GTP because it has picked up another phosphate group. It then gives it energy to have other reactions within the cell.
What happens when GTP is bound to the G protein
The subunits split- alpha, beta and gamma
Alpha protein goes to another effector protein
Beta and gamma proteins both go to other effector proteins
What are effector proteins
Proteins that are sitting in the membrane waiting to be activated via a G protein coupled receptor and then cause other cascades within the neuron
What cascade is activated by the G protein
Second messenger cascades, which is how information is spread within the neuron
As well as activating second messenger cascades, what else do G proteins activate?
The opening of ion channels
What happens after the G protein has been activated
The membrane returns to normal, alpha breaks GTP back to GDP
What can second messenger systems activate?
Downstream activation of enzymes important to neuronal function
What is a second messenger system
Regulation of systems within the neuron to respond to information that the neuron has received from outside transmitters
Why do we have second messenger systems?
More sophisticated transfer of information as many systems can be involved
Amplification of the signal- one receptor can effect many downstream systems
What does an inhibitory G protein do?
Prevent the second messenger system cascade
What is receptor feedback
When feedback is provided to the presynaptic neuron to stop releasing neurotransmitter
What does endogenous mean
Chemicals that are in the body
What does exogenous mean
Chemicals that are applied to the body
What is an agonist
It binds to a receptor and has an effect on the neuron
What is an antagonist receptor
Binds to the receptor but doesn’t have an effect on the neuron
