Synaptic Transmission Flashcards
What is the “active zone” of a presynaptic neuron?
The end of the presynaptic neuron near the synapse where synaptic vesicles are clustered.
Which ion is the presynaptic neuron dependent on for synaptic vesicle fusion and neurotransmitter release?
Ca2+
What does the term “quanta” refer to with regards to neurotransmitters?
It refers to the fact that each synaptic vesicle has roughly equal amounts of neurotransmitter and that the amount of neurotransmitter released into the cleft is an integral multiple of the number of NT in each vesicle.
What are SNARE molecules and what do they do?
The SNARE molecules are synaptobrevin, syntaxin, and SNAP-25. They are involved in Ca2+-dependent fusion of synaptic vesicles to the neuronal plasma membrane.
What does synaptobrevin do?
A molecule in the synaptic vesicle that forms a tight-coil interaction with syntaxin in the neuronal plasma membrane and SNAP-25 in the cytoplasm to bring the vesicle close to the plasma membrane, ready for fusion.
What is synaptotagmin and how does it work?
A molecule in the synaptic vesicle membrane that acts as the fusion brake under resting conditions. When Ca2+ enters the neuron, Ca2+ binds to synaptotagmin to induce a conformational change and release of the brake –> membrane fusion.
What is the excitatory neurotransmitter of the CNS?
Glutamate
What does botulinum toxin do to SNAREs?
Hydrolyzes them –> flaccid paralysis
What are the two basic types of neurotransmitter receptors?
Ionotropic and metabotropic
What is the difference between ionotropic and metabotropic receptors?
Ionotropic receptors bind the transmitter molecules and also form an ion-permeable trans-membrane pore.
Metabotropic receptors bind neurotransmitters and activate a GTP-binding protein, which then alters the permeability of a separate ion channel.
Which receptor results in faster neurotransmission: ionotropic or metabotropic?
Ionotropic
What neuronal cell types most commonly summate afferent potentials?
Integrative CNS neurons.
What are the five ways in which the strength of a synapse can be physiologically altered?
- Change post-synaptic receptor density.
- Change the probability of pre-synaptic vesicle fusion.
- Change the activity of Ca2+ channels in nerve terminals.
- Change the post-synaptic threshold.
- Change the equilibrium potential.
Are ligand-gated ion channels often permeable to multiple ion species? Name an example.
Yeah. Ach receptors let Na+ in but also let K+ out of the cell.
What is the “reversal potential?”
The membrane potential at which driving force of Na+ into the cell equals the driving force of K+ out of the cell as in multi-permeable Ach receptor channels.
