Excitatory and inhibitory Neurotransmission in the CNS
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what are the 2 major families of ligand gated channels?
GABA, Glycine and ACh receptors (pentamers) Glutamate receptors (tetramers) classified as non-NMDA (fast excitatory) and NMDA (slow excitatory) receptors Metabotropic glutamate receptors modulate role of NT
Effects of the following drugs inreltion to GABA receptors: Benzodiazepines Barbiturates Baclofen
GABA is inhibitory (so is glycine) • positive allosteric modulator of the GABA receptor so enhance Cl entry, decrease rmp and enhance inhibition in presence of GABA • similar to bentos, potentates effect of GABA at GABAa receptor • agonist of the GABAb receptor so enhances K current and increases inhibition
Give definitions: EPSP IPSP Graded potential Glutamate GABA interneurone Projection neurone Excitatory neurone Inhibitory neurone quanta
A depolarizing change in rmp caused by the actions of excitatory neurotransmission. Multiple EPSPs or very large EPSPs can cause rmp to cross threshold and result in an Action Potential (AP) negative change in rmp caused by release of an inhibitory neurotransmitter. Inhibits crossing of the threshold and inhibits AP. a change in the rmp caused by an EPSP or IPSP, such a change is caused by (inhibitory or excitatory) neurotransmitter release and is not of a magnitude large enough to cross threshold and result in an AP The major excitatory neurotransmitter, acts on ionotropic receptors to allow Na and Ca in and K out of the cell, net result is an EPSP, depolarization, and excitation. The major inhibitory neurotransmitter, acts on ionotropic receptors to allow Cl into the cell, net result is an IPSP, hyperpolarization, and inhibition A locally-acting neurone, typically releases GABA and so brings about an IPSP and inhibition, function is local processing of information A neuron responsible for conveying signals to other parts of the brain, typically releases Glutamate and so brings about an EPSP Releases a depolarizing neurotransmitter (e.g. glutamate) Releases a hyperpolarizing neurotransmitter (e.g. GABA) The release of NT form a single vesicle
factors influencing the outcome of nuerotransmission?
NT might be excitatory or inhibitory neurone may have different receptor types responding to single presynaptic event influence of a synapse depends on the distance the current has to travel to the neurones trigger zone varying quanta released neurone has multiple synaptic contacts from multiple cells excitatory and inhibitory synapses have competitive actions