Synaptic Transmission: Post-Synaptic Flashcards
What’s the difference between an electrical synapse and a chemical synapse?
Electric - no delay, bidirectional and very fast (via gap junctions)
Chemical - delay of about 0.5-1 ms per synapse, unidirectional
What is an EPSP vs IPSP?
Excitatory vs inhibitory post synaptic potential. Excitatory are depolarizing, inhibitory are hyperpolarizing. They can be graded in size
What is spatial vs temporal summation?
Spatial - multiple neurons at the same time can fire to reach threshold potential by adding their small EPSPs
Temporal - Neurons firing repeatedly can depolarize before the repolarization period is over, and sum closer to threshold potential to trigger AP.
These can be mixed effects
How does the glutamate receptor depend on the voltage of the post-synaptic neuron, and what is the mechanism behind this?
At lower potentials, the glutamate response is short and quick. At higher potentials, it is longlasting and slower. This is because NMDA channels are activated more at higher potentials, while AMPA channels are Always active.
NMDA channels allow ions to flow through only when the potential in the cell is high enough to displace a magnesium which blocks the channel.
What causes the fast and slow EPSP responses of cholinergic receptors?
Fast: Nicotinic - nonselective ion channels open
Slow: Muscarinic - inhibit the potassium M receptor via GPCR to induce a steady-state depolarization, making the neuron more excitable.
What is the effect of norepinephrine on the hippocampus, and how does this contrast with acetylcholine?
It has a “modulatory effect”, making neurons more excitable WITHOUT modifying membrane potential. This occurs via inhibition of potassium channels involved in repolarization, so the neuron is more excitable in the relative refractory period
For patch clamping a receptor, which way signifies current flow into the cell?
A downward deflection. There are no halfway openings.
What are the cholinergic receptor types to the autonomic ganglion cells, striated muscles, and CNS?
Four classes of fibers Type 1: Postganglionic PANS - M only Type 2: Preganglionic SANS/PANS - both M / N Type 3: Somatic Motor - N only Type 4: CNS - both M / N
keep in mind there are different subtypes of these receptors
What are GABA-A vs GABA-B receptors?
Ligand-gated chloride channels, which also bind others.
GABA-A: Responsive to benzodiazepines i.e. Valium. used as anticonvulsant + sedative
GABA-B: Activated by Baclofen, which treats muscle spasms
What does alpha-bungarotoxin bind?
Nicotinic receptors specifically
What is the mechanism by which cholera toxin works?
Irreversible activation of GalphaS in the enterocytes to keep Chloride channels open and lead to osmotic pressure out of the cells.
What is the mechanism of action for pertussis toxin?
Blocks the muscarinic inhibition of the heart by modifying Gk (hyperpolarizing) and Gi (anti-cAMP, hyperpolarizing).
What is the mechanism of action of nitric oxide?
Diffuse thru membrane directly into post-synaptic cell, activating guanylate cyclase. This activates G-kinases via cGMP (you know the rest, viagra).
