Darkthorn’s Blog

Synapse – Speed and Efficiency

Presynaptic – neurotransmitter ready for release (release mechanisms present)

Synapse – effective communication pathway (where transmitter removal occurs)

Postsynaptic – receptive molecules (five sub units, each with 4 membrane spanning regions)

Neurotransmitter – synthesized in advance, then stored in vesicles

Within a bouton – similar numbers of neurotransmitter per vesicle, vesicles anchored to filaments (and docking sites)

Postsynaptic receptors become ion channels when a transmitter binds the TM2 helices move apart to allow ions through (ionotropic channels), then close. The neurotransmitter is able to bind to a large extracellular domain.

- sodium enters cells as potassium leaves

- net positive influx, depolarization

- graded fast response

each release site dispenses only one vesicle per action potential

quantal release results in EPSPs (ESPs) of approximately equal value

- amplitude depends on number and properties of receptors

- reaches threshold and increases probability of opening Na+ channels

Cl- inhibits the action potential, preventing it from reaching the threshold

Glutamate & Acetylcholine – excitatory ionotropic receptors

GABA and Glycine – inhibitory ionotropic receptors