Lecture 3: Modulation of Membrane Potential Flashcards
What are the two different types of synapses?
chemical and electrical
How do ligand-gated ion channels work?
neurotransmitter binds -> channel opens -> ions flow across membrane
How do GPCRs work?
neurotransmitter binds -> G-protein is activated -> G-protein subunits or intracellular messengers modulate ion channels -> ion channel opens -> ions flow across membrane
Are ionotropic receptors fast or slow?
fast
Are metabotropic receptors fast or slow?
slow
What are the different types of neurotransmitter?
acetylcholine, amino acids, purines, catecholamines, indoleamines, imidazoleamines and peptides
What are the three main classes of ionotropic receptors and what is their division based upon?
AMPA, NMDA and kainate
divided into families based on their pharmacology
What is the subunit of a receptor determined by?
genes
What are the features of a receptor subunit?
amino terminus and carboxy terminus
transmembrane spanning domain
What do multiple receptor subunits form?
a pore / channel
How can different receptors be made?
different combinations of receptor subunits
What is the nature of AMPA channels? Will more sodium or potassium initially pass through these channels?
non-selective cation channels which allow equal passage of sodium and potassium -> initially larger proportion of sodium moving through the channel
What is the nature of NMDA channels?
glutamate binding to NMDA receptor opens a channel that transmits Ca2+, Na+ and K+
What are glutamate ion channels made up of?
subunits which have three membrane-spanning domains and a re-entrant loop
most models predict four subunits making up an ion channel
How is glutamate removed from the synaptic cleft?
EATTs present on astrocytes transport glutamate into the cell to that it can be converted to glutamine and inactivated -> glutamine is then taken up by EATTs present on the presynaptic terminal and converted back to glutamate
Are acetylcholine receptors ionotropic or metabotropic?
both
nicotinic receptor = ionotropic
muscarinic receptor = metabotropic
What are nicotinic receptors important for?
somatic movement
How is acetylcholine inactivated?
acetylcholinesterase breaks down ACh to acetate and choline
What are nicotinic receptors and what are they made up of?
non-selective cation channels
they are made of pentamers of four transmembrane spanning domains
What are gap junctions composed of and what do they enable?
molecules such as connexins
electrical synapses
How do electrical synapses work?
enable direct passage of ions between neurons -> this ionic movement alters the postsynaptic membrane potential
Is there such thing as mixed synapses?
yes
What are ionotropic receptors made of?
collections of protein subunits that interact to form a pore
What is the effect of opening a non-selective ion channel dependent on?
the membrane potential and the transmembrane ion concentrations
