Sünapsidel

Sünapsidel is the Estonian term for synapses, the junctions through which neurons relay signals in the nervous system. In the nervous system, a synapse connects the presynaptic neuron with a postsynaptic neuron or effector cell. Most synapses are chemical, with a presynaptic terminal releasing neurotransmitters into a narrow synaptic cleft, which then bind to receptors on the postsynaptic membrane. A smaller number are electrical, formed by gap junctions that allow direct ionic current flow.

The presynaptic component contains synaptic vesicles loaded with neurotransmitters. Arrival of an action potential opens voltage-gated calcium channels, triggering vesicle fusion via SNARE proteins and transmitter release. Neurotransmitters diffuse across the cleft and bind to receptors, producing excitatory or inhibitory postsynaptic potentials. Receptors include ionotropic receptors that mediate fast responses and metabotropic receptors that produce slower, longer-lasting effects through second messenger systems.

Synaptic strength changes through plasticity. Long-term potentiation (LTP) and long-term depression (LTD) adjust the efficacy of transmission and are central to learning and memory. Short-term plasticity, such as facilitation or depression, shapes signaling on shorter time scales. During development, synaptogenesis creates connections, followed by synaptic pruning to refine networks.

Dysfunction at Sünapsidel can contribute to neurological and psychiatric disorders, including Alzheimer's disease, autism spectrum disorders, epilepsy, and schizophrenia. Treatments may target neurotransmitter systems, receptor function, or signaling cascades to modulate synaptic activity.