Neuroscience - Neural Communication & Synaptic Transmission

Presynaptic ${\text{Ca}}^{2+}$ influx binds to Synaptotagmin (the ${\text{Ca}}^{2+}$ sensor). This triggers interaction with the SNARE complex (v-SNARE: Synaptobrevin; t-SNAREs: Syntaxin-1 and SNAP-25), forcing the synaptic vesicle to fuse with the presynaptic membrane and release neurotransmitters via exocytosis.

Ionotropic Receptors: Ligand-gated ion channels that open directly upon ligand binding, mediating rapid, short-duration responses (e.g., AMPA, ${\text{GABA}}_A$).
Metabotropic Receptors: G-protein coupled receptors (GPCRs) that activate second messenger cascades, producing slower, longer-lasting modulatory effects (e.g., $\text{mGluR}$, ${\text{GABA}}_B$).

EPSP (Excitatory Postsynaptic Potential): Local depolarization caused by cation influx (e.g., ${\text{Na}}^{+}$, ${\text{Ca}}^{2+}$), shifting $V_m$ closer to threshold.
IPSP (Inhibitory Postsynaptic Potential): Local hyperpolarization caused by anion influx (e.g., ${\text{Cl}}^{-}$) or cation efflux (e.g., ${\text{K}}^{+}$), moving $V_m$ away from threshold.

The primary excitatory neurotransmitter in the central nervous system.

The primary inhibitory neurotransmitters of the nervous system.

Key neurotransmitter at the neuromuscular junction (NMJ), autonomic ganglia, and central cholinergic pathways.

Temporal Summation: Addition of multiple postsynaptic potentials generated by a single presynaptic axon firing repeatedly at high frequency.
Spatial Summation: Addition of simultaneous postsynaptic potentials originating from multiple distinct presynaptic inputs at different dendritic locations.

A persistent strengthening of a synapse following high-frequency stimulation (tetanus). High ${\text{Ca}}^{2+}$ influx through NMDA receptors activates kinases (such as CaMKII), triggering insertion of additional AMPA receptors into the postsynaptic membrane to enhance synaptic responsiveness.