Receptor mechanisms I Flashcards
A chemical is nothing without its
Receptor
What happens when a hormone/neurotransmitter binds to specific receptor
There will be an effect in that cell
What will an antagonist do
Will have no effect on the cell and it stops the receptor from working
What is the order of speed from fastest to slowest when it comes to receptors
- Ligand gated ion channels
- G-protein coupled
- Tyrosine kinase linked and nuclear receptors
What is the receptor of a ligand gated ion channel
Its an ion channel
What does binding of an agonist cause on a ligand gated ion channel
Causes a conformational change, opening the ion channel, creating an instant ion flow
What is a nicotine cholinoreceptor stimulated by
Acetylcholine
What is a 5HT3 receptor stimulated by
5-HT (serotonin)
What ions do the nicotine cholinoreceptor and the 5HT3 receptor use and what happens to the membrane potential
They both use Na and Ca
The membrane potential depolarises (-70mv to 0mv)
What is the GABAa receptor stimulated by
gamma-aminobutyric acid (GABA)
What is the glycine receptor stimulated by
Glycine
What ion does the GABAa and glycine receptor use and what happens to the membrane potential
They both use Cl
The membrane hyperpolarises
What is the structure of the basic protein forming the parts of the ligand gated ion channel
- Big amino terminus
- 4 transmembrane domains
- 2nd domain is differentiated from the other 3
What does a functional ligand gated ion channel require
- 5 of these grouped domains, so overall there are 20 domains
- The second domain group is situated in the middle and therefore forms the ion pathway
How is the structure of the ligand gated ion channel related to its function
Hydrophilic amino acids are on the outside of the plasma membrane
Hydrophobic/lipophilic amino acids are on the inside of the plasma membrane, therefore the transmembrane domains will be hydrophobic amino acids
How many molecules are required to open the pentamer
2 molecules of agonist e.g. acetylcholine
Where are N1/Nm nicotinic receptors found
They are found in motor end plates on skeletal muscle cells in the neuromuscular junction
Where are N2/Nn nicotinic receptors found
Found in cholinergic and adrenergic ganglia, the CNS and the adrenal medulla
Whats the difference between adult and foetal N1 muscle nicotinic receptors and why
Foetal ion channel takes longer to open and close since it has gamma subunit instead of an epsilon subunit (Alpha-1, gamma, alpha-1, beta-1 and delta)
What is the cause of Myasthesia gravis
Antibodies attack the alpha-1 subunit in N1 muscle nicotinic acetylcholine receptors causing the number of functioning receptors to drop. N2 neuronal nicotinic receptors are unaffected
What are the diagnosable differences of Myasthesia gravis
The electrical recording of the resting potential in the neuromuscular junction presents with very little miniature end plate potentials
What are the symptoms of Myasthesia gravis
Muscle weakness, dropping eyelids, fatigue, difficulty swallowing
What does the GABAa receptor do once stimulated
causes an inhibitory effect on neurotransmission by diminishing the chance of a successful action potential occurring
